The Limits to Growth: A report for the Club of Rome's project on the predicament of
mankind
AuthorMeadows, Donella H.
AuthorMeadows, Dennis L.
AuthorRanders, Jørgen
AuthorBehrens, William W., III
Date1972
Access and Usage RightsPublished with permission of Dennis Meadows, Jørgen Randers, William Behrens
III, the Sustainability Institute (on behalf of lead author Donella
Meadows), and William Watts, President of Potomac Associates. Dartmouth
College Library assigns a Creative Commons BY-NC license
(http://creativecommons.org/licenses/by-nc/3.0/deed.en_US)to the digital
work and associated web site.
About this Transcription
Literalversion preserves the author's original text, including abbreviations and historical
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THE LIMITS TO GROWTH
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A POTOMAC ASSOCIATES BOOK
THE LIMITS TO GROWTH
A REPORT FOR THE CLUB OF ROME'S PROJECT ON THE
PREDICAMENT OF MANKIND
Donella H. Meadows
Dennis L. Meadows
Jørgen Randers
William W. Behrens III
Universe Books.
NEW YORK:
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All rights reserved. No part of this publication may be reproduced, stored in a
retrieval system, or transmitted in any form or by any means, electronic,
mechanical, photocopying, recording, or otherwise, without the prior permission
of Potomac Associates.
Second printing before publication 1972 Third printing 1972 Fourth
printing 1972 Fifth printing 1972
To Dr. Aurelio Peccei, whose profound concern for humanity has
inspired us and many others to think about the world's long–term
problems
Untitled/Unnumbered Page
The MIT Project Team
Dr. Dennis L. Meadows, director, United
States
Dr. Alison A. Anderson, United States (pollution)
Dr. Jay M. Anderson, United States (pollution)
Ilyas Bayar, Turkey (agriculture)
William W. Behrens III, United States (resources)
Farhad Hakimzadeh, Iran (population)
Dr. Steffen Harbordt, Germany (socio–political trends)
Judith A. Machen, United States (administration)
Dr. Donella H. Meadows, United States (population)
Peter Milling, Germany (capital)
Nirmala S. Murthy, India (population)
Roger F. Naill, United States (resources)
Jørgen Randers, Norway (pollution)
Stephen Shantzis, United States (agriculture)
John A. Seeger, United States (administration)
Marilyn Williams, United States (documentation)
Dr. Erich K. O. Zahn, Germany (agriculture)
Page 9
FOREWORD
IN APRIL 1968, a group of thirty individuals from ten countries—scientists,
educators, economists, humanists, industrialists, and national and international
civil servants—gathered in the Accademia dei Lincei in Rome. They met at
the instigation of Dr. Aurelio Peccei, an Italian industrial manager, economist,
and man of vision, to discuss a subject of staggering scope—the present
and future predicament of man.
THE CLUB OF ROME
Out of this meeting grew The Club of Rome, an informal organization that has been
aptly described as an "invisible college." Its purposes are to foster
understanding of the varied but interdependent components—economic,
political, natural, and social—that make up the global system in which we
all live; to bring that new understanding to the attention of
policy–makers and the public worldwide; and in this way to promote new
policy initiatives and action.
The Club of Rome remains an informal international association,
with a membership that has now grown to approximately seventy persons of
twenty–five nationalities. None of its members holds public office, nor
does the group seek to express any single ideological, political, or national
point of view. All are united, however, by their overriding conviction that the
major problems facing mankind are of such complexity and are so interrelated
that traditional institutions and policies are
Page 10
FOREWORD
no longer able to cope with them, nor even to come to grips
with their full content.
The members of The Club of Rome have backgrounds as varied as their
nationalities. Dr. Peccei, still the prime moving force within the group, is
affiliated with Fiat and Olivetti and manages a consulting firm for economic and
engineering development, Italconsult, one of the largest of its kind in Europe.
Other leaders of The Club of Rome include: Hugo Thiemann, head of the Battelle
Institute in Geneva; Alexander King, scientific director of the Organization for
Economic Cooperation and Development; Saburo Okita, head of the Japan Economic
Research Center in Tokyo; Eduard Pestel of the Technical University of Hannover,
Germany; and Carroll Wilson of the Massachusetts Institute of Technology.
Although membership in The Club of Rome is limited, and will not exceed one
hundred, it is being expanded to include representatives of an ever greater
variety of cultures, nationalities, and value systems.
THE PROJECT ON THE PREDICAMENT OF MANKIND
A series of early meetings of The Club of Rome culminated in the decision to
initiate a remarkably ambitious undertaking —the Project on the
Predicament of Mankind.
The intent of the project is to examine the complex of problems
troubling men of all nations: poverty in the midst of plenty; degradation of the
environment; loss of faith in institutions; uncontrolled urban spread;
insecurity of employment; alienation of youth; rejection of traditional values;
and inflation and other monetary and economic disruptions. These seemingly
divergent parts of the "world problematique," as The Club of Rome calls it, have
three characteristics in com–
Page 11
FOREWORD
mon: they occur to some degree in all societies; they contain
technical, social, economic, and political elements; and, most important of all,
they interact.
It is the predicament of mankind that man can perceive the
problematique, yet, despite his considerable knowledge and skills, he does not
understand the origins, significance, and interrelationships of its many
components and thus is unable to devise effective responses. This failure occurs
in large part because we continue to examine single items in the problematique
without understanding that the whole is more than the sum of its parts, that
change in one element means change in the others.
Phase One of the Project on the Predicament of Mankind took
definite shape at meetings held in the summer of 1970 in Bern, Switzerland, and
Cambridge, Massachusetts. At a two–week conference in Cambridge, Professor
Jay Forrester of the Massachusetts Institute of Technology (MIT) presented a
global model that permitted clear identification of many specific components of
the problematique and suggested a technique for analyzing the behavior and
relationships of the most important of those components. This presentation led
to initiation of Phase One at MIT, where the pioneering work of Professor
Forrester and others in the field of System Dynamics had created a body of
expertise uniquely suited to the research demands.
The Phase One study was conducted by an international team, under
the direction of Professor Dennis Meadows, with financial support from the
Volkswagen Foundation. The team examined the five basic factors that determine,
and therefore, ultimately limit, growth on this planet—population,
agricultural production, natural resources, industrial production,
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FOREWORD
and pollution. The research has now been completed. This book
is the first account of the findings published for general readership.
A GLOBAL CHALLENGE
It is with genuine pride and pleasure that Potomac Associates joins with The Club
of Rome and the MIT research team in the publication of The Limits
to Growth.
We, like The Club of Rome, are a young organization, and we believe
the Club's goals are very close to our own. Our purpose is to bring new ideas,
new analyses, and new approaches to persistent problems—both national and
international—to the attention of all those who care about and help
determine the quality and direction of our life. We are delighted therefore to
be able to make this bold and impressive work available through our book
program.
We hope that The Limits to Growth will command critical attention
and spark debate in all societies. We hope that it will encourage each reader to
think through the consequences of continuing to equate growth with progress. And
we hope that it will lead thoughtful men and women in all fields of endeavor to
consider the need for concerted action now if we are to preserve the
habitability of this planet for ourselves and our children.
"I do not wish to seem overdramatic, but I can only conclude from the
information that is available to me as Secretary–General, that the Members
of the United Nations have perhaps ten years left in which to subordinate their
ancient quarrels and launch a global partnership to curb the arms race, to
improve the human environment, to defuse the population explosion, and to supply
the required momentum to development efforts. If such a global partnership is
not forged within the next decade, then I very much fear that the problems I
have mentioned will have reached such staggering proportions that they will be
beyond our capacity to control."
U THANT, 1969
The problems U Thant mentions— the arms race,
environmental deterioration, the population explosion, and economic
stagnation—are often cited as the central, long–term problems of
modern man. Many people believe that the future course of human society, perhaps
even the survival of human society, depends on the speed and effectiveness with
which the world responds to these issues. And yet only a small fraction of the
world's population is actively concerned with understanding these problems or
seeking their solutions.
HUMAN PERSPECTIVES
Every person in the world faces a series of pressures and problems that require
his attention and action. These problems
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INTRODUCTION
affect him at many different levels. He may spend much of
his time trying to find tomorrow's food for himself and his family. He may be
concerned about personal power or the power of the nation in which he lives. He
may worry about a world war during his lifetime, or a war next week with a rival
clan in his neighborhood.
These very different levels of human concern can be represented on
a graph like that in figure 1. The graph has two dimensions, space and time.
Every human concern can be located at some point on the graph, depending on how
much geographical space it includes and how far it extends in time. Most
people's worries are concentrated in the lower left–hand corner of the
graph. Life for these people is difficult, and they must devote nearly all of
their efforts to providing for themselves and their families, day by day. Other
people think about and act on problems farther out on the space or time axes.
The pressures they perceive involve not only themselves, but the community with
which they identify. The actions they take extend not only days, but weeks or
years into the future.
A person's time and space perspectives depend on his culture, his
past experience, and the immediacy of the problems confronting him on each
level. Most people must have successfully solved the problems in a smaller area
before they move their concerns to a larger one. In general the larger the space
and the longer the time associated with a problem, the smaller the number of
people who are actually concerned with its solution.
There can be disappointments and dangers in limiting one's view to
an area that is too small. There are many examples of a person striving with all
his might to solve some immediate, local problem, only to find his efforts
defeated by events occurring in a larger context. A farmer's carefully
maintained
Page 19
INTRODUCTION
fields can be destroyed by an international war. Local officials' plans
can be overturned by a national policy. A country's economic development can be
thwarted by a lack of world demand for its products. Indeed there is increasing
concern today that most personal and national objectives may ultimately be
frustrated by long–term, global trends such as those mentioned by U
Thant.
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INTRODUCTION
Are the implications of these global trends actually so threatening
that their resolution should take precedence over local, short–term
concerns?
Is it true, as U Thant suggested, that there remains less than a
decade to bring these trends under control?
If they are not brought under control, what will the consequences
be?
What methods does mankind have for solving global problems, and
what will be the results and the costs of employing each of them?
These are the questions that we have been investigating in the
first phase of The Club of Rome's Project on the Predicament of Mankind. Our
concerns thus fall in the upper right–hand corner of the space–time
graph.
PROBLEMS AND MODELS
Every person approaches his problems, wherever they occur on the space–time
graph, with the help of models. A model is simply an ordered set of assumptions
about a complex system. It is an attempt to understand some aspect of the
infinitely varied world by selecting from perceptions and past experience a set
of general observations applicable to the problem at hand. A farmer uses a
mental model of his land, his assets, market prospects, and past weather
conditions to decide which crops to plant each year. A surveyor constructs a
physical model—a map—to help in planning a road. An economist uses
mathematical models to understand and predict the flow of international
trade.
Decision–makers at every level unconsciously use mental
models to choose among policies that will shape our future world. These mental
models are, of necessity, very simple when
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INTRODUCTION
compared with the reality from which they are abstracted.
The human brain, remarkable as it is, can only keep track of a limited number of
the complicated, simultaneous interactions that determine the nature of the real
world.
We, too, have used a model. Ours is a formal, written model of the
world.* It constitutes a preliminary attempt to
improve our mental models of long–term, global problems by combining the
large amount of information that is already in human minds and in written
records with the new information–processing tools that mankind's
increasing knowledge has produced—the scientific method, systems analysis,
and the modern computer.
Our world model was built specifically to investigate five major
trends of global concern—accelerating industrialization, rapid population
growth, widespread malnutrition, depletion of nonrenewable resources, and a
deteriorating environment. These trends are all interconnected in many ways, and
their development is measured in decades or centuries, rather than in months or
years. With the model we are seeking to understand the causes of these trends,
their interrelationships, and their implications as much as one hundred years in
the future.
The model we have constructed is, like every other model,
imperfect, oversimplified, and unfinished. We are well aware of its
shortcomings, but we believe that it is the most useful model now available for
dealing with problems far out on the space–time graph. To our knowledge it
is the only formal model in existence that is truly global in scope, that has a
* The prototype model on which we have
based our work was designed by Professor Jay W. Forrester of the
Massachusetts Institute of Technology. A description of that model has been
published in his book World Dynamics
(Cambridge, Mass.: :
Wright–Allen Press., 1971).
Page 22
INTRODUCTION
time horizon longer than thirty years, and that includes
important variables such as population, food production, and pollution, not as
independent entities, but as dynamically interacting elements, as they are in
the real world.
Since ours is a formal, or mathematical, model it also has two
important advantages over mental models. First, every assumption we make is
written in a precise form so that it is open to inspection and criticism by all.
Second, after the assumptions have been scrutinized, discussed, and revised to
agree with our best current knowledge, their implications for the future
behavior of the world system can be traced without error by a computer, no
matter how complicated they become.
We feel that the advantages listed above make this model unique
among all mathematical and mental world models available to us today. But there
is no reason to be satisfied with it in its present form. We intend to alter,
expand, and improve it as our own knowledge and the world data base gradually
improve.
In spite of the preliminary state of our work, we believe it is
important to publish the model and our findings now. Decisions are being made
every day, in every part of the world, that will affect the physical, economic,
and social conditions of the world system for decades to come. These decisions
cannot wait for perfect models and total understanding. They will be made on the
basis of some model, mental or written, in any case. We feel that the model
described here is already sufficiently developed to be of some use to
decision–makers. Furthermore, the basic behavior modes we have already
observed in this model appear to be so fundamental and general that we do not
expect our broad conclusions to be substantially altered by further
revisions.
Page 23
INTRODUCTION
It is not the purpose of this book to give a complete, scientific
description of all the data and mathematical equations included in the world
model. Such a description can be found in the final technical report of our
project Rather, in The Limits to Growth we summarize the main
features of the model and our findings in a brief, nontechnical way. The
emphasis is meant to be not on the equations or the intricacies of the model,
but on what it tells us about the world. We have used a computer as a tool to
aid our own understanding of the causes and consequences of the accelerating
trends that characterize the modern world, but familiarity with computers is by
no means necessary to comprehend or to discuss our conclusions. The implications
of those accelerating trends raise issues that go far beyond the proper domain
of a purely scientific document. They must be debated by a wider community than
that of scientists alone. Our purpose here is to open that debate.
The following conclusions have emerged from our work so far. We are
by no means the first group to have stated them. For the past several decades,
people who have looked at the world with a global, long–term perspective
have reached similar conclusions. Nevertheless, the vast majority of
policymakers seems to be actively pursuing goals that are inconsistent with
these results.
Our conclusions are:
1. If the present growth trends in world population,
industrialization, pollution, food production, and resource depletion
continue unchanged, the limits to growth on this planet will be reached
sometime within the next one hundred years. The most probable result will be
a rather sudden and uncontrollable decline in both population and industrial
capacity.
Page 24
INTRODUCTION
2. It is possible to alter these growth trends and to establish a
condition of ecological and economic stability that is sustainable far into
the future. The state of global equilibrium could be designed so that the
basic material needs of each person on earth are satisfied and each person
has an equal opportunity to realize his individual human potential.
3. If the world's people decide to strive for this second outcome
rather than the first, the sooner they begin working to attain it, the
greater will be their chances of success.
These conclusions are so far–reaching and raise so many questions for
further study that we are quite frankly overwhelmed by the enormity of the job
that must be done. We hope that this book will serve to interest other people,
in many fields of study and in many countries of the world, to raise the space
and time horizons of their concerns and to join us in understanding and
preparing for a period of great transition— the transition from growth to
global equilibrium.
Page 25
CHAPTER I THE NATURE OF
EXPONENTIAL GROWTH
"People at present think that five sons are not too many and each son has
five sons also, and before the death of the grandfather there are already 25
descendants. Therefore people are more and wealth is less; they work hard
and receive little."
HAN FEI-TZU, ca. 500 B.C.
All five elements basic to the study reported
here—population, food production, industrialization, pollution, and
consumption of nonrenewable natural resources—are increasing. The amount
of their increase each year follows a pattern that mathematicians call
exponential growth. Nearly all of mankind's current activities, from use of
fertilizer to expansion of cities, can be represented by exponential growth
curves (see figures 2 and 3). Since much of this book deals with the causes and
implications of exponential growth curves, it is important to begin with an
understanding of their general characteristics.
THE MATHEMATICS OF EXPONENTIAL GROWTH
Most people are accustomed to thinking of growth as a linear process. A quantity is growing linearly when it increases
by a
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THE NATURE OF EXPONENTIAL GROWTH
constant amount in a constant time period. For example, a child who becomes
one inch taller each year is growing linearly. If a miser hides $10 each
year under his mattress, his
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THE NATURE OF EXPONENTIAL GROWTH
horde of money is also increasing in a linear way. The amount of increase
each year is obviously not affected by the size of the child nor the amount
of money already under the mattress.
A quantity exhibits exponential growth
when it increases by a constant percentage of the whole in a constant time
period. A colony of yeast cells in which each cell divides into two cells
every 10 minutes is growing exponentially. For each single cell, after 10
minutes there will be two cells, an increase
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THE NATURE OF EXPONENTIAL GROWTH
of 100 percent. After the next 10 minutes there will be four cells, then
eight, then sixteen. If a miser takes $100 from his mattress and invests it
at 7 percent (so that the total amount accumulated increases by 7 percent
each year), the invested money will grow much faster than the linearly
increasing stock under the mattress (see figure 4). The amount added each
year to a bank account or each 10 minutes to a yeast colony is not constant.
It continually increases, as the total accumulated amount increases. Such
exponential growth is a common process in biological, financial, and many
other systems of the world.
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THE NATURE OF EXPONENTIAL GROWTH
Common as it is, exponential growth can yield surprising
results—results that have fascinated mankind for centuries. There is
an old Persian legend about a clever courtier who presented a beautiful
chessboard to his king and requested that the king give him in return 1
grain of rice for the first square on the board, 2 grains for the second
square, 4 grains for the third, and so forth. The king readily agreed and
ordered rice to be brought from his stores. The fourth square of the
chessboard required 8 grains, the tenth square took 512 grains, the
fifteenth required 16,384, and the twenty-first square gave the courtier
more than a million grains of rice. By the fortieth square a million million
rice grains had to be brought from the storerooms. The king's entire rice
supply was exhausted long before he reached the sixty-fourth square.
Exponential increase is deceptive because it generates immense numbers very
quickly.
A French riddle for children illustrates another aspect of
exponential growth—the apparent suddenness with which it approaches a
fixed limit. Suppose you own a pond on which a water lily is growing. The
lily plant doubles in size each day. If the lily were allowed to grow
unchecked, it would completely cover the pond in 30 days, choking off the
other forms of life in the water. For a long time the lily plant seems
small, and so you decide not to worry about cutting it back until it covers
half the pond. On what day will that be? On the twenty–ninth day, of
course. You have one day to save your pond.*
It is useful to think of exponential growth in terms of doubling time, or the time it takes a growing
quantity to
* We are indebted to M. Robert Lattes for telling us this
riddle.
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THE NATURE OF EXPONENTIAL GROWTH
double in size. In the case of the lily plant described above, the doubling
time is 1 day. A sum of money left in a bank at 7 percent interest will
double in 10 years. There is a simple mathematical relationship between the
interest rate, or rate of growth, and the time it will take a quantity to
double in size. The doubling time is approximately equal to 70 divided by
the growth rate, as illustrated in table 1.
Scroll Table to show more columns
Table 1: DOUBLING TIME
Growth rate (% per
year)
Doubling time (years)
0.1
700
0.5
140
1.0
70
2.0
35
4.0
18
5.0
14
7.0
10
10.0
7
MODELS AND EXPONENTIAL GROWTH
Exponential growth is a dynamic phenomenon, which means that it involves
elements that change over time. In simple systems, like the bank account or
the lily pond, the cause of exponential growth and its future course are
relatively easy to understand. When many different quantities are growing
simultaneously in a system, however, and when all the quantities are
interrelated in a complicated way, analysis of the causes of growth and of
the future behavior of the system becomes very difficult indeed. Does
population growth cause industrialization or does industrialization cause
population growth? Is either one singly responsible for increasing
pol–
Page 31
THE NATURE OF EXPONENTIAL GROWTH
lution, or are they both responsible? Will more food production result in
more population? If any one of these elements grows slower or faster, what
will happen to the growth rates of all the others? These very questions are
being debated in many parts of the world today. The answers can be found
through a better understanding of the entire complex system that unites all
of these important elements.
Over the course of the last 30 years there has evolved at the
Massachusetts Institute of Technology a new method for understanding the
dynamic behavior of complex systems. The method is called System
Dynamics.* The basis of the method is the recognition that the structure of any system—the many circular,
interlocking, sometimes time-delayed relationships among its
components—is often just as important in determining its behavior as
the individual components themselves. The world model described in this book
is a System Dynamics model.
Dynamic modeling theory indicates that any exponentially
growing quantity is somehow involved with a positive
feedback loop. A positive feedback loop is sometimes called a
"vicious circle." An example is the familiar wage–price
spiral—wages increase, which causes prices to increase, which leads to
demands for higher wages, and so forth. In a positive feedback loop a chain
of cause–and–effect relationships closes on itself, so that
increasing any one element in the loop will start a sequence of changes that
will result in the originally changed element being increased even
more.
* A detailed description of the method
of System Dynamics analysis is presented in J. W. Forrester's Industrial Dynamics (Cambridge, Mass.: MIT
Press, 1961) and Principles of Systems
(Cambridge, Mass.: Wright-Allen Press, 1968).
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THE NATURE OF EXPONENTIAL GROWTH
The positive feedback loop that accounts for exponential
increase of money in a bank account can be represented like this:
Suppose $100 is deposited in the account. The first year's
interest is 7 percent of $100, or $7, which is added to the account, making
the total $107. The next year's interest is 7 percent of $107, or $7.49,
which makes a new total of $114.49. One year later the interest on that
amount will be more than $8.00. The more money there is in the account, the
more money will be added each year in interest. The more is added, the more
there will be in the account the next year causing even more to be added in
interest. And so on. As we go around and around the loop, the accumulated
money in the account grows exponentially. The rate of interest (constant at
7 percent) determines the gain around the loop, or the rate at which the
bank account grows.
We can begin our dynamic analysis of the long-term world
situation by looking for the positive feedback loops underlying the
exponential growth in the five physical quantities we have already
mentioned. In particular, the growth rates of two of these
elements—population and industrialization—are of interest, since
the goal of many development policies is to encourage the growth of the
latter relative to the former. The
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THE NATURE OF EXPONENTIAL GROWTH
two basic positive feedback loops that account for exponential population
and industrial growth are simple in principle. We will describe their basic
structures in the next few pages. The many interconnections between these
two positive feedback loops act to amplify or to diminish the action of the
loops, to couple or uncouple the growth rates of population and of industry.
These interconnections constitute the rest of the world model and their
description will occupy much of the rest of this book.
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THE NATURE OF EXPONENTIAL GROWTH
WORLD POPULATION GROWTH
The exponential growth curve of world population is shown in figure 5. In
1650 the population numbered about 0.5 billion,* and it was
growing at a rate of approximately 0.3 percent per year.1 That corresponds to a doubling time of nearly 250 years. In
1970 the population totaled 3.6 billion and the rate of growth was 2.1
percent per year.2 The doubling time at this growth
rate is 33 years. Thus, not only has the population been growing
exponentially, but the rate of growth has also been growing. We might say
that population growth has been "super"–exponential; the population
curve is rising even faster than it would if growth were strictly
exponential.
The feedback loop structure that represents the dynamic
behavior of population growth is shown below.
On the left is the positive feedback loop that accounts for
the observed exponential growth. In a population with constant average
fertility, the larger the population, the more babies will be born each
year. The more babies, the larger the popula-
*The word "billion" in this book will be used to mean 1000
million, i.e. the European "milliard."
1 Notes
begin on page 201.
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THE NATURE OF EXPONENTIAL GROWTH
tion will be the following year. After a delay to allow those babies to grow
up and become parents, even more babies will be born, swelling the
population still further. Steady growth will continue as long as average
fertility remains constant. If, in addition to sons, each woman has on the
average two female children, for example, and each of them grows up to have
two more female children, the population will double each generation. The
growth rate will depend on both the average fertility and the length of the
delay between generation's. Fertility is not necessarily constant, of
course, and in chapter III we will discuss some of the factors that cause it
to vary.
There is another feedback loop governing population growth,
shown on the right side of the diagram above. It is a negative feedback loop. Whereas positive feedback loops generate
runaway growth, negative feedback loops tend to regulate growth and to hold
a system in some stable state. They behave much as a thermostat does in
controlling the temperature of a room. If the temperature falls, the
thermostat activates the heating system, which causes the temperature to
rise again. When the temperature reaches its limit, the thermostat cuts off
the heating system, and the temperature begins to fall again. In a negative
feedback loop a change in one element is propagated around the circle until
it comes back to change that element in a direction opposite to the initial change.
The negative feedback loop controlling population is based
upon average mortality, a reflection of the general health of the
population. The number of deaths each year is equal to the total population
times the average mortality (which we might think of as the average
probability of death at any age).
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THE NATURE OF EXPONENTIAL GROWTH
An increase in the size of a population with constant average mortality will
result in more deaths per year. More deaths will leave fewer people in the
population, and so there will be fewer deaths the next year. If on the
average 5 percent of the population dies each year, there will be 500 deaths
in a population of 10,000 in one year. Assuming no births for the moment,
that would leave 9,500 people the next year. If the probability of death is
still 5 percent, there will be only 475 deaths in this smaller population,
leaving 9,025 people. The next year there will be only 452 deaths. Again,
there is a delay in this feedback loop because the mortality rate is a
function of the average age of the population. Also, of course, mortality
even at a given age is not necessarily constant.
If there were no deaths in a population, it would grow
exponentially by the positive feedback loop of births, as shown below. If
there were no births, the population would decline
to zero because of the negative feedback loop of deaths, also as shown
below. Since every real population experiences both
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THE NATURE OF EXPONENTIAL GROWTH
births and deaths, as well as varying fertility and mortality, the dynamic
behavior of populations governed by these two interlocking feedback loops
can become fairly complicated.
What has caused the recent super–exponential rise in
world population? Before the industrial revolution both fertility and
mortality were comparatively high and irregular. The birth rate generally
exceeded the death rate only slightly, and population grew exponentially,
but at a very slow and uneven rate. In 1650 the average lifetime of most
populations in the world was only about 30 years. Since then, mankind has
developed many practices that have had profound effects on the population
growth system, especially on mortality rates. With the spread of modern
medicine, public health techniques, and new methods of growing and
distributing foods, death rates have fallen around the world. World average
life expectancy is currently about 53 years3 and still
rising. On a world average the gain around the positive feedback loop
(fertility) has decreased only slightly while the gain around the negative
feedback loop (mortality) is decreasing. The result is an increasing
dominance of the positive feedback loop and the sharp exponential rise in
population pictured in figure 5.
What about the population of the future? How might we extend
the population curve of figure 5 into the twenty-first century? We will have
more to say about this in chapters III and IV. For the moment we can safely
conclude that because of the delays in the controlling feedback loops,
especially the positive loop of births, there is no possibility of leveling
off the population growth curve before the year 2000, even with the most
optimistic assumption of decreasing fertility. Most of the prospective
parents of the year 2000 have already been born. Unless there is a sharp
rise in mortality,
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THE NATURE OF EXPONENTIAL GROWTH
which mankind will certainly strive mightily to avoid, we can look forward
to a world population of around 7 billion persons in 30 more years. And if
we continue to succeed in lowering mortality with no better success in
lowering fertility than we have accomplished in the past, in 60 years there
will be four people in the world for every one person living today.
WORLD ECONOMIC GROWTH
A second quantity that has been increasing in the world even faster than
human population is industrial output. Figure 6
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THE NATURE OF EXPONENTIAL GROWTH
shows the expansion of world industrial production since 1930, with 1963
production as the base of reference. The average growth rate from 1963 to
1968 was 7 percent per year, or 5 percent per year on a per capita
basis.
What is the positive feedback loop that accounts for
exponential growth of industrial output? The dynamic structure, diagramed
below, is actually very similar to the one we have already described for the
population system.
With a given amount of industrial capital (factories, trucks,
tools, machines, etc.), a certain amount of manufactured output each year is
possible. The output actually produced is also dependent on labor, raw
materials, and other inputs. For the moment we will assume that these other
inputs are sufficient, so that capital is the limiting factor in production.
(The world model does include these other inputs.) Much of each year's
output is consumable goods, such as textiles, automobiles, and houses, that
leave the industrial system. But some fraction of the production is more
capital—looms, steel mills, lathes—which is an investment to
increase the capital stock. Here we have another positive feedback loop.
More capital creates more
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THE NATURE OF EXPONENTIAL GROWTH
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THE NATURE OF EXPONENTIAL GROWTH
output, some variable fraction of the output is investment, and more
investment means more capital. The new, larger capital stock generates even
more output, and so on. There are also delays in this feedback loop, since
the production of a major piece of industrial capital, such as an electrical
generating plant or a refinery, can take several years.
Capital stock is not permanent. As capital wears out or
becomes obsolete, it is discarded. To model this situation we must introduce
into the capital system a negative feedback loop accounting for capital
depreciation. The more capital there is, the more wears out on the average
each year; and the more that wears out, the less there will be the next
year. This negative feedback loop is exactly analogous to the death rate
loop in the population system. As in the population system, the positive
loop is strongly dominant in the world today, and the world's industrial
capital stock is growing exponentially.
Since industrial output is growing at 7 percent per year and
population only at 2 percent per year, it might appear that dominant
positive feedback loops are a cause for rejoicing. Simple extrapolation of
those growth rates would suggest that the material standard of living of the
world's people will double within the next 14 years. Such a conclusion,
however, often includes the implicit assumption that the world's growing
industrial output is evenly distributed among the world's citizens. The
fallacy of this assumption can be appreciated when the per capita economic
growth rates of some individual nations are examined (see figure 7).
Most of the world's industrial growth plotted in figure 6 is
actually taking place in the already industrialized countries, where the
rate of population growth is comparatively low.
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THE NATURE OF EXPONENTIAL GROWTH
Scroll Table to show more columns
Table 2: ECONOMIC AND POPULATION GROWTH RATES
Country
Population (1968) (million)
Average annual growth rate of population (1961–69) (% per
year)
GNP per
capita (1968) (US dollars)
Average annual growth rate of GNP per
capita (1961-68) (% per year)
The most revealing possible illustration of that fact is a simple table
listing the economic and population growth rates of the ten most populous
nations of the world, where 64 percent of the world's population currently
lives. Table 2 makes very clear the basis for the saying,
"The rich
get richer and the poor get children."
It is unlikely that the rates of growth listed in table 2 will
continue unchanged even until the end of this century. Many
*The International Bank for Reconstruction and Development
qualifies its estimates for China and the USSR with the following statement:
"Estimates of GNP per capita and its growth rate have a wide margin of error
mainly because of the problems in deriving the GNP at factor cost from net
material product and in converting the GNP estimate into US dollars." United
Nations estimates are in general agreement with those of the IBRD. SOURCE:
World Bank Atlas
(Washington,DC: : International Bank
for Reconstruction and Development., 1970).
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THE NATURE OF EXPONENTIAL GROWTH
factors will change in the next 30 years. The end of civil disturbance in
Nigeria, for example, will probably increase the economic growth rate there,
while the onset of civil disturbance and then war in Pakistan has already
interfered with economic growth there. Let us recognize, however, that the
growth rates listed above are the products of a complicated social and
economic system that is essentially stable and that is likely to change
slowly rather than quickly, except in cases of severe social
disruption.
It is a simple matter of arithmetic to calculate extrapolated
values for gross national product (GNP) per capita from now until the year
2000 on the assumption that relative growth rates of population and GNP will
remain roughly the same in these ten countries. The result of such a
calculation appears in table 3. The values shown there will almost certainly
not actually be realized. They are not
predictions. The values merely indicate the general direction our system, as
it is currently structured, is taking us. They demonstrate
that the process of
*Based on the 1968 dollar with no allowance for
inflation.
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THE NATURE OF EXPONENTIAL GROWTH
economic growth, as it is occurring today, is inexorably
widening the absolute gap between the rich and the poor nations of the
world.
Most people intuitively and correctly reject extrapolations
like those shown in table 3, because the results appear ridiculous. It must
be recognized, however, that in rejecting extrapolated values, one is also
rejecting the assumption that there will be no change
in the system. If the extrapolations in table 3 do not actually come to
pass, it will be because the balance between the positive and negative
feedback loops determining the growth rates of population and capital in
each nation has been altered. Fertility, mortality, the capital investment
rate, the capital depreciation rate—any or all may change. In
postulating any different outcome from the one shown in table 3, one must
specify which of these factors is likely to change, by how much, and when.
These are exactly the questions we are addressing with our model, not on a
national basis, but on an aggregated global one.
To speculate with any degree of realism on future growth rates
of population and industrial capital, we must know something more about the
other factors in the world that interact with the population-capital system.
We shall begin by asking a very basic set of questions.
Can the growth rates of population and capital presented in
table 3 be physically sustained in the world? How many people can be
provided for on this earth, at what level of wealth, and for how long? To
answer these questions, we must look in detail at those systems in the world
which provide the physical support for population and economic growth.
Page 45
CHAPTER II THE LIMITS TO
EXPONENTIAL GROWTH
"For which of you, intending to build a tower, sitteth not down first, and
counteth the cost, whether he have sufficient to finish it?"
LUKE 14:28
What will be needed to sustain world economic and
population growth until, and perhaps even beyond, the year 2000? The list of
necessary ingredients is long, but it can be divided roughly into two main
categories.
The first category includes the physical
necessities that support all physiological and industrial activity—food,
raw materials, fossil and nuclear fuels, and the ecological systems of the
planet which absorb wastes and recycle important basic chemical substances.
These ingredients are in principle tangible, countable items, such as arable
land, fresh water, metals, forests, the oceans. In this chapter we will assess
the world's stocks of these physical resources, since they are the ultimate
determinants of the limits to growth on this earth.
The second category of necessary ingredients for growth consists
of the social necessities. Even if the earth's physical
systems are capable of supporting a much larger, more econom–
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THE LIMITS TO EXPONENTIAL GROWTH
ically developed population, the actual growth of the economy and of the
population will depend on such factors as peace and social stability, education
and employment, and steady technological progress. These factors are much more
difficult to assess or to predict. Neither this book nor our world model at this
stage in its development can deal explicitly with these social factors, except
insofar as our information about the quantity and distribution of physical
supplies can indicate possible future social problems.
Food, resources, and a healthy environment are necessary but not
sufficient conditions for growth. Even if they are abundant, growth may be
stopped by social problems. Let us assume for the moment, however, that the best
possible social conditions will prevail. How much growth will the physical
system then support? The answer we obtain will give us some estimate of the
upper limits to population and capital growth, but no guarantee that growth will
actually proceed that far.
FOOD
In Zambia, in Africa, 260 of every thousand babies born are dead before
their first birthday. In India and Pakistan the ratio is 140 of every
thousand; in Colombia it is 82. Many more die before they reach school age;
others during the early school years.
Where death certificates are issued for preschool infants in
the poor countries, death is generally attributed to measles, pneumonia,
dysentery, or some other disease. In fact these children are more likely to
be the victims of malnutrition.4
No one knows exactly how many of the world's people are
inadequately nourished today, but there is general agreement that the number
is large—perhaps 50 to 60 percent of the population of the less
industrialized countries,5 which means one-third of the
population of the world. Estimates by the
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THE LIMITS TO EXPONENTIAL GROWTH
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THE LIMITS TO EXPONENTIAL GROWTH
UN Food and Agriculture Organization (FAO) indicate that in most of the
developing countries basic caloric requirements, and particularly protein
requirements, are not being supplied (see figure 8). Furthermore, although
total world agricultural production is increasing, food production per capita in the nonindustrialized countries is
barely holding constant at its present inadequate level (see figure 9). Do
these rather dismal statistics mean that the limits of food production on
the earth have already been reached?
The primary resource necessary for producing food is land.
Recent studies indicate that there are, at most, about 3.2 billion hectares
of land (7.86 billion acres) potentially suitable for agriculture on the
earth.6 Approximately half of that land, the richest,
most accessible half, is under cultivation today. The remaining land will
require immense capital inputs to reach, clear, irrigate, or fertilize
before it is ready to produce food. Recent costs of developing new land have
ranged from $215 to $5,275 per hectare. Average cost for opening land in
unsettled areas has been $1,150 per hectare.7 According to an FAO report,
opening more land to cultivation is not economically feasible, even given
the pressing need for food in the world today:
In Southern Asia ... in some countries in Eastern Asia, in the Near East and
North Africa, and in certain parts of Latin America and Africa . . . there
is almost no scope for expanding the arable area.
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THE LIMITS TO EXPONENTIAL GROWTH
. . . In the dryer regions it will even be necessary to return to permanent
pasture the land which is marginal or submarginal for cultivation. In most
of Latin America and Africa South of the Sahara there are still considerable
possibilities for expanding cultivated area, but the costs of development
are high and it will be often more economical to intensify utilization of
the areas already settled.8
If the world's people did decide to pay the high capital costs,
to cultivate all possible arable land, and to produce as much food as
possible, how many people could theoretically be fed?
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THE LIMITS TO EXPONENTIAL GROWTH
The lower curve in figure 10 shows the amount of land needed to feed the
growing world population, assuming that the present world average of 0.4
hectares per person is sufficient. (To feed the entire world population at
present US standards, 0.9 hectares per person would be required.) The upper
curve in figure 10 shows the actual amount of arable land available over
time. This line, slopes downward because each additional person requires a
certain amount of land (0.08 hectares per
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THE LIMITS TO EXPONENTIAL GROWTH
person assumed here *) for housing, roads, waste disposal,
power lines, and other uses that essentially
"pave"
arable land
and make it unusable for food production. Land loss through erosion is not
shown here, but it is by no means negligible. Figure 10 shows that, even
with the optimistic assumption that all possible land is utilized, there
will still be a desperate land shortage before the year 2000 if per capita
land requirements and population growth rates remain as they are today.
Figure 10 also illustrates some very important general facts
about exponential growth within a limited space. First, it shows how one can
move within a very few years from a situation of great abundance to one of
great scarcity. There has been an overwhelming excess of potentially arable
land for all of history, and now, within 30 years (or about one population
doubling time), there may be a sudden and serious shortage. Like the owner
of the lily pond in our example in chapter I, the human race may have very
little time to react to a crisis resulting from exponential growth in a
finite space.
A second lesson to be learned from figure 10 is that precise
numerical assumptions about the limits of the earth are unimportant when
viewed against the inexorable progress of exponential growth. We might
assume, for example, that no arable land is taken for
cities, roads, or other nonagricultural uses. In that case, the land
available is constant, as shown by the horizontal dashed line. The point at
which the two curves cross is delayed by about 10 years. Or we can suppose
that it is possible to double, or even quadruple, the productivity of the
land through advances in agricultural technology and in–
*Aerial surveys of forty-four counties in the western United
States from 1950 to 1960 indicate that built-on land ranged from .008 to
.174 hectares per person.9
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THE LIMITS TO EXPONENTIAL GROWTH
vestments in capital, such as tractors, fertilizer, and irrigation systems.
The effects of two different assumptions about increased productivity are
shown by the dotted lines in figure 10. Each doubling of productivity gains
about 30 years, or less than one population doubling time.
Of course, society will not be suddenly surprised by the
"crisis point" at which the amount of land needed becomes greater than that
available. Symptoms of the crisis will begin to appear long before the
crisis point is reached. Food prices will rise so high that some people will
starve; others will be forced to decrease the effective amount of land they
use and shift to lower quality diets. These symptoms are already apparent in
many parts of the world. Although only half the land shown in figure 10 is
now under cultivation, perhaps 10 to 20 million deaths each year can be
attributed directly or indirectly to malnutrition.10
There is no question that many of these deaths are due to the
world's social limitations rather than its physical ones. Yet there is
clearly a link between these two kinds of limitations in the food-producing
system. If good fertile land were still easily reached and brought under
cultivation, there would be no economic barrier to feeding the hungry, and
no difficult social choices to make. The best half of the world's
potentially arable land is already cultivated, however, and opening new land
is already so costly that society has judged it "uneconomic." This is a
social problem exacerbated by a physical limitation.
Even if society did decide to pay the necessary costs to gain
new land or to increase productivity of the land already cultivated, figure
10 shows how quickly rising population would bring about another "crisis
point." And each successive crisis point will cost more to overcome. Each
doubling of yield
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THE LIMITS TO EXPONENTIAL GROWTH
from the land will be more expensive than the last one. We might call this
phenomenon the law of increasing costs. The best and most sobering example
of that law comes from an assessment of the cost of past agricultural gains.
To achieve a 34 percent increase in world food production from 1951 to 1966,
agriculturalists increased yearly expenditures on tractors by 63 percent,
annual investment in nitrate fertilizers by 146 percent, and annual use of
pesticides by 300 percent.11 The next 34 percent increase
will require even greater inputs of capital and resources.
How many people can be fed on this earth? There is, of course,
no simple answer to this question. The answer depends on the choices society
makes among various available alternatives. There is a direct
trade–off between producing more food and producing other goods and
services needed or desired by mankind. The demand for these other goods and
services is also increasing as population grows, and therefore the
trade–off becomes continuously more apparent and more difficult to
resolve. Even if the choice were consistently to produce food as the first
priority, however, continued population growth and the law of increasing
costs could rapidly drive the system to the point where all available
resources were devoted to producing food, leaving no further possibility of
expansion.
In this section we have discussed only one possible limit to
food production—arable land. There are other possible limits, but
space does not permit us to discuss them in detail here. The most obvious
one, second in importance only to land, is the availability of fresh water.
There is an upper limit to the fresh water runoff from the land areas of the
earth each year, and there is also an exponentially increasing demand for
that water. We could draw a graph exactly analogous to figure 10
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THE LIMITS TO EXPONENTIAL GROWTH
to show the approach of the increasing demand curve for water to the
constant average supply. In some areas of the world, this limit will be
reached long before the land limit becomes apparent.
It is also possible to avoid or extend these limits by
technological advances that remove dependence on the land (synthetic food)
or that create new sources of fresh water (desalinization of sea water). We
shall discuss such innovations further in chapter IV. For the moment it is
sufficient to recognize that no new technology is spontaneous or without
cost. The factories and raw materials to produce synthetic food, the
equipment and energy to purify sea water must all come from the physical
world system.
The exponential growth of demand for
food results directly from the positive feedback loop that is now
determining the growth of human population. The supply of food to be expected in the future is dependent on land
and fresh water and also on agricultural capital, which depends in turn on
the other dominant positive feedback loop in the system—the capital
investment loop. Opening new land, farming the sea, or expanding use of
fertilizers and pesticides will require an increase of the capital stock
devoted to food production. The resources that permit growth of that capital
stock tend not to be renewable resources, like land or water, but
nonrenewable resources, like fuels or metals. Thus the expansion of food
production in the future is very much dependent on the availability of
nonrenewable resources. Are there limits to the earth's supply of these
resources?
NONRENEWABLE RESOURCES
Even taking into account such economic factors as increased prices with
decreasing availability, it would appear at present that the
quanti–
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THE LIMITS TO EXPONENTIAL GROWTH
ties of platinum, gold, zinc, and lead are not sufficient to meet demands.
At the present rate of expansion . . . silver, tin, and uranium may be in
short supply even at higher prices by the turn of the century. By the year
2050, several more minerals may be exhausted if the current rate of
consumption continues.
Despite spectacular recent discoveries, there are only a
limited number of places left to search for most minerals. Geologists
disagree about the prospects for finding large, new, rich ore deposits.
Reliance on such discoveries would seem unwise in the long term.12
Table 4 lists some of the more important mineral and fuel
resources, the vital raw materials for today's major industrial processes.
The number following each resource in column 3 is the static reserve index,
or the number of years present known reserves of that resource (listed in
column 2) will last at the current rate of usage.
This static index is the measure normally used to express future resource
availability. Underlying the static index are several assumptions, one of
which is that the usage rate will remain constant.
But column 4 in table 4 shows that the world usage rate of
every natural resource is growing exponentially. For many resources the
usage rate is growing even faster than the population, indicating both that
more people are consuming resources each year and also that the average
consumption per person is increasing each year. In other words, the
exponential growth curve of resource consumption is driven by both the
positive feedback loops of population growth and of capital growth.
We have already seen in figure 10 that an exponential increase
in land use can very quickly run up against the fixed amount of land
available. An exponential increase in resource consumption can rapidly
diminish a fixed store of resources in the same way. Figure 11, which is
similar to figure 10, illus–
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THE LIMITS TO EXPONENTIAL GROWTH
Scroll Table to show more columns
Table 4 NONRENEWABLE NATURAL RESOURCES
1
2
3
4
5
6
Resource
Known Global Reservesa
Static Index (years)b
Projected Rate of
Growth (% per year)c High Av.
Low
Exponen– tial Index (years)d
Exponen– tial
Index Calculated Using 5
Times Known Reserves (years)e
Aluminum
1.17X109 tons j
100
7.7 6.4 5.1
31
55
Chromium
7.75X108 tons
420
3.3 2.6 2.0
95
154
Coal
5X1012 tons
2300
5.3 4.1 3.0k
111
150
Cobalt
4.8X109 lbs
110
2.0 1.5 1.0
60
148
Copper
308X106 tons
36
5.8 4.6 3.4
21
48
Gold
353X106 troy oz
11
4.7 4.1 3.4l
9
29
Iron
1X1011 tons
240
2.3 1.8 1.3
93
173
Lead
91X106 tons
26
2.4 2.0 1.7
21
64
Manganese
8X108 tons
97
3.5 2.9 2.4
46
94
Mercury
3.34X106 flasks
13
3.1 2.6 2.2
13
41
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THE LIMITS TO EXPONENTIAL GROWTH
Scroll Table to show more columns
7
8
9
10
Countries or Areas with Highest Reserves (% of world
total) f
Prime Producers (% of
world total) g
Prime consumers (% of
world total)h
US Con– sumption as % of World Totali
Australia (33) Guinea (20) Jamaica (10)
Jamaica (19) Surinam (12)
US (42) USSR (12)
42
Rep. of S. Africa (75)
USSR (30) Turkey (10)
19
US (32) USSR–China (53)
USSR (20) US (13)
44
Rep. of Congo (31) Zambia (16)
Rep. of Congo (51)
32
US (28) Chile (19)
US (20) USSR (15) Zambia (13)
US (33) USSR (13) Japan (11)
33
Rep. of S. Africa (40)
Rep. of S. Africa (77) Canada (6)
26
USSR (33) S. Am. (18) Canada (14)
USSR (25) US (14)
US (28) USSR (24) W. Germany (7)
28
US (39)
USSR (13) Australia (13) Canada (11)
US (25) USSR (13) W. Germany (11)
25
Rep. of S. Afraica (38) USSR (25)
USSR (34) Brazil (13) Rep. of S. Africa (13)
14
Spain (30) Italy (21)
Spain (22) Italy (21) USSR (18)
24
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THE LIMITS TO EXPONENTIAL GROWTH
Scroll Table to show more columns
1
2
3
4
5
6
Resource
Known Global Reservesa
Static Index (years)b
Projected Rate of
Growth (% per year)c High Av.
Low
Exponen– tial
Index (years)d
Exponen– tial
Index Calculated Using 5
Times Known Reserves (years)
Molybdenum
10.8X109 lbs
79
5.0 4.5 4.0
34
65
Natural Gas
1.14X1015 cu ft
38
5.5 4.7 3.9
22
49
Nickel
147X109 lbs
150
4.0 3.4 2.8
53
96
Petroleum
455X109 bbls
31
4.9 3.9 2.9
20
50
Platinum Groupm
429X106 troy oz
13
4.5 3.8 3.1
47
85
Silver
5.5X109 troy oz
16
4.0 2.7 1.5
13
42
Tin
4.3X106 lg tons
17
2.3 1.1 0
15
61
Tungsten
2.9X109 lbs
40
2.9 2.5 2.1
28
72
Zinc
123X106 tons
23
3.3 2.9 2.5
18
50
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THE LIMITS TO EXPONENTIAL GROWTH
Scroll Table to show more columns
7
8
9
10
Countries or Areas with Highest Reserves (% of world
total)f
Prime Producers (% of
world total)g
Prime Consumers (% of
world total)h
US Con– sumption as % of World Totali
US (58) USSR (20)
US (64) Canada (14)
40
US (25) USSR (20)
US (58) USSR (18)
63
Cuba (25) New Caledonia (22) USSR (14) Canada
(14)
Canada (42) New Caledonia (28) USSR (16)
38
Saudi Arabia (17) Kuwait (15)
US (23) USSR (16)
US (33) USSR (12) Japan (6)
33
Rep. of S. Africa (47) USSR (47)
USSR (59)
31
Communist Countries (36) US (24)
Canada (20) Mexico (17) Peru (16)
US (26) W. Germany (11)
26
Thailand (33) Malaysia (14)
Malaysia (41) Bolivia (16) Thailand (13)
US (24) Japan (14)
24
China (73)
China (25) USSR (19) US (14)
22
US (27) Canada (20)
Canada (23) USSR (11) US (8)
US (26) Japan (13) USSR (11)
26
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THE LIMITS TO EXPONENTIAL GROWTH
a SOURCE: US Bureau of
Mines, Mineral Facts and Problems, 1970
(Washington, DC: : Government
Printing Office., 1970).
b The number of years known global reserves will
last at current global consumption. Calculated by dividing known reserves
(column 2) by the current annual consumption (US Bureau of
Mines, Mineral Facts and Problems,
1970).
c SOURCE: US Bureau of
Mines, Mineral Facts and Problems,
1970.
d The number of years known global reserves will
last with consumption growing exponentially at the average annual rate of
growth. Calculated by the formula exponential index = In ((r*s) + 1) / r
where r = average rate of growth from column 4
s = static index from column 3.
e The number of years that five times known
global reserves will last with consumption growing exponentially at the
average annual rate of growth. Calculated from the above formula with 5s in
place of s.
f SOURCE: US Bureau of
Mines, Mineral Facts and Problems, 1970.
g SOURCE: UN Department of
Economic and Social Affairs, Statistical Yearbook
1969 (New York: : United
Nations., 1970).
h SOURCES:
Yearbook of the American Bureau of Metal Statistics 1970
(York, Pa.: :Maple Press.,
1970). World Petroleum Report (New York: :
Mona Palmer Publishing., 1968). UN Economic Commission for Europe, The World Market for Iron
Ore (New York: : United
Nations., 1968).
US Bureau of Mines, Mineral Facts and
Problems, 1970.
i SOURCE:
US Bureau of Mines, Mineral Facts and Problems,
1970.
j Bauxite expressed in aluminum equivalent.
k US Bureau of Mines contingency forecasts,
based on assumptions that coal will be used to synthesize gas and liquid
fuels.
l Includes US Bureau of Mines estimates of gold
demand for hoarding.
m The platinum group metals are platinum,
palladium, iridium, osmium, rhodium, and ruthenium.
ADDITIONAL SOURCES:
P. T. Flawn, Mineral Resources
(Skokie, Ill.: : Rand
McNally., 1966).
Metal Statistics (Somerset, NJ: :
American Metal Market Company., 1970).
US Bureau of Mines, Commodity Data
Summary (Washington, DC: :
Government Printing Office., January 1971).
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trates the effect of exponentially increasing consumption of a given initial
amount of a nonrenewable resource. The example in this case is chromium ore,
chosen because it has one of the longest static reserve indices of all the
resources listed in table 4. We could draw a similar graph for each of the
resources listed in the table. The time scales for the resources would vary,
but the general shape of the curves would be the same.
The world's known reserves of chromium are about 775 million
metric tons, of which about 1.85 million metric tons are mined annually at
present.13 Thus, at the current rate of
use, the known reserves would last about 420 years. The dashed line in
figure 11 illustrates the linear depletion of chromium reserves that would
be expected under the assumption of constant use. The actual world
consumption of chromium is increasing, however, at the rate of 2.6 percent
annually.13 The curved solid lines in
figure 11 show how that growth rate, if it continues, will deplete the
resource stock, not in 420 years, as the linear assumption indicates, but in
just 95 years. If we suppose that reserves yet undiscovered could increase
present known reserves by a factor of five, as shown by the dotted line,
this fivefold increase would extend the lifetime of the reserves only from
95 to 154 years. Even if it were possible from 1970 onward to recycle 100
percent of the chromium (the horizontal line) so that none of the initial
reserves were lost, the demand would exceed the supply in 235 years.
Figure 11 shows that under conditions of exponential growth in
resource consumption, the static reserve index (420 years for chromium) is a
rather misleading measure of resource availability. We might define a new
index, an exponential reserve index," which gives the probable lifetime of
each resource, assuming that the current growth rate in consumption will
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continue. We have included this index in column 5 of table 4. We have also
calculated an exponential index on the assumption that our present known
reserves of each resource can be expanded fivefold by new discoveries. This
index is shown in column 6. The effect of exponential growth is to reduce
the probable period of availability of aluminum, for example, from 100 years
to 31 years (55 years with a fivefold increase in reserves). Copper, with a
36–year lifetime at the present usage
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rate, would actually last only 21 years at the present rate of growth, and
48 years if reserves are multiplied by five. It is clear that the present
exponentially growing usage rates greatly diminish the length of time that
wide–scale economic growth can be based on these raw materials.
Of course the actual nonrenewable resource availability in the
next few decades will be determined by factors much more complicated than
can be expressed by either the simple static reserve index or the
exponential reserve index. We have studied this problem with a detailed
model that takes into account the many interrelationships among such factors
as varying grades of ore, production costs, new mining technology, the
elasticity of consumer demand, and substitution of other resources.* Illustrations of the general conclusions of this model
follow.
Figure 12 is a computer plot indicating the future availability
of a resource with a 400–year static reserve index in the year 1970,
such as chromium. The horizontal axis is time in years; the vertical axis
indicates several quantities, including the amount of reserves remaining
(labeled RESERVES), the amount used each year (USAGE RATE), the extraction
cost per unit of resource (ACTUAL COST), the advance of mining and
processing technology (indicated by a T), and the fraction of original use
of the resource that has been shifted to a substitute resource (F).
At first the annual consumption of chromium grows
exponentially, and the stock of the resource is rapidly depleted. The price
of chromium remains low and constant because new developments in mining
technology allow efficient use of lower
*A more complete description of this model is presented in
the papers by William W. Behrens III listed in the appendix.
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and lower grades of ore. As demand continues to increase, however, the
advance of technology is not fast enough to counteract the rising costs of
discovery, extraction, processing,
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and distribution. Price begins to rise, slowly at first and then very
rapidly. The higher price causes consumers to use chromium more efficiently
and to substitute other metals for chromium whenever possible. After 125
years, the remaining chromium, about 5 percent of the original supply, is
available
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only at prohibitively high cost, and mining of new supplies has fallen
essentially to zero.
This more realistic dynamic assumption about the future use of
chromium yields a probable lifetime of 125 years, which is considerably
shorter than the lifetime calculated from the static assumption (400 years),
but longer than the lifetime calculated from the assumption of constant
exponential growth (95 years). The usage rate in the dynamic model is
neither constant nor continuously increasing, but bell-shaped, with a growth
phase and a phase of decline.
The computer run shown in figure 13 illustrates the effect of a
discovery in 1970 that doubles the remaining known
chromium reserves. The static reserve index in 1970 becomes 800 years
instead of 400. As a result of this discovery, costs remain low somewhat
longer, so that exponential growth can continue longer than it did in figure
12. The period during which use of the resource is economically feasible is
increased from 125 years to 145 years. In other words, a doubling of the reserves increases the actual period of use by
only 20 years.
The earth's crust contains vast amounts of those raw materials
which man has learned to mine and to transform into useful things. However
vast those amounts may be, they are not infinite. Now that we have seen how
suddenly an exponentially growing quantity approaches a fixed upper limit,
the following statement should not come as a surprise. Given present resource consumption rates and the projected increase in
these rates, the great majority of the currently important nonrenewable
resources will be extremely costly ioo years from now. The above
statement remains true regardless of the most optimistic assumptions about
undiscovered reserves, technological advances, substitution, or recycling,
as long as the
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demand for resources continues to grow exponentially. The prices of those
resources with the shortest static reserve indices have already begun to
increase. The price of mercury, for example, has gone up 500 percent in the
last 20 years; the price of lead has increased 300 percent in the last 30
years.14
The simple conclusions we have drawn by considering total world
reserves of resources are further complicated by the fact that neither
resource reserves nor resource consumption are distributed evenly about the
globe. The last four columns of table 4 show clearly that the
industrialized, consuming countries are heavily dependent on a network of
international agreements with the producing countries for the supply of raw
materials essential to their industrial base. Added to the difficult
economic question of the fate of various industries as resource after
resource becomes prohibitively expensive is the imponderable political
question of the relationships between producer and consumer nations as the
remaining resources become concentrated in more limited geographical areas.
Recent nationalization of South American mines and successful Middle Eastern
pressures to raise oil prices suggest that the political question may arise
long before the ultimate economic one.
Are there enough resources to allow the economic development of
the 7 billion people expected by the year 2000 to a reasonably high standard
of living? Once again the answer must be a conditional one. It depends on
how the major resource–consuming societies handle some important
decisions ahead. They might continue to increase resource consumption
according to the present pattern. They might learn to reclaim and recycle
discarded materials. They might develop new designs to increase the
durability of products made from scarce
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resources. They might encourage social and economic patterns that would
satisfy the needs of a person while minimizing, rather than maximizing, the
irreplaceable substances he possesses and disperses.
All of these possible courses involve trade–offs. The
trade–offs are particularly difficult in this case because they
involve choosing between present benefits and future benefits. In order to
guarantee the availability of adequate resources in the future, policies
must be adopted that will decrease resource use in the present. Most of
these policies operate by raising resource costs. Recycling and better
product design are expensive; in most parts of the world today they are
considered "uneconomic." Even if they were effectively instituted, however,
as long as the driving feedback loops of population and industrial growth
continue to generate more people and a higher resource demand per capita,
the system is being pushed toward its limit—the depletion of the
earth's nonrenewable resources.
What happens to the metals and fuels extracted from the earth
after they have been used and discarded? In one sense they are never lost.
Their constituent atoms are rearranged and eventually dispersed in a diluted
and unusable form into the air, the soil, and the waters of our planet. The
natural ecological systems can absorb many of the effluents of human
activity and reprocess them into substances that are usable by, or at least
harmless to, other forms of life. When any effluent is released on a large
enough scale, however, the natural absorptive mechanisms can become
saturated. The wastes of human civilization can build up in the environment
until they become visible, annoying, and even harmful. Mercury in ocean
fish, lead particles in city air, mountains of urban trash, oil slicks on
beaches—these are the results of the increasing flow of
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resources into and out of man's hands. It is little wonder, then, that
another exponentially increasing quantity in the world system is pollution.
POLLUTION
Many people . . . are concluding on the basis of mounting and reasonably
objective evidence that the length of life of the biosphere as an
inhabitable region for organisms is to be measured in decades rather than in
hundreds of millions of years. This is entirely the fault of our own
species.15
Man's concern for the effect of his activities on the natural
environment is only very recent. Scientific attempts to measure this effect
are even more recent and still very incomplete. We are certainly not able,
at this time, to come to any final conclusion about the earth's capacity to
absorb pollution. We can, however, make four basic points in this section,
which illustrate, from a dynamic, global perspective, how difficult it will
be to understand and control the future state of our ecological systems.
These points are:
1. The few kinds of pollution that actually have been measured
over time seem to be increasing exponentially.
2. We have almost no knowledge about where the upper limits to
these pollution growth curves might be.
3. The presence of natural delays in ecological processes
increases the probability of underestimating the control measures
necessary, and therefore of inadvertently reaching those upper limits.
4. Many pollutants are globally distributed; their harmful effects
appear long distances from their points of generation.
It is not possible to illustrate each of these four points for each type of
pollutant, both because of the space limitations
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of this book and because of the limitations of available data. Therefore we
shall discuss each point using as examples those pollutants which have been
most completely studied to date. It is not necessarily true that the
pollutants mentioned here are the ones of greatest concern (although they
are all of some concern). They are, rather, the ones we understand best.
Exponentially increasing pollution
Virtually every pollutant that has been measured as a function of time
appears to be increasing exponentially. The rates of increase of the
various examples shown below vary greatly, but most are growing faster
than the population. Some pollutants are obviously directly related to
population growth (or agricultural activity, which is related to
population growth). Others are more closely related to the growth of
industry and advances in technology. Most pollutants in the complicated
world system are influenced in some way by both
the population and the industrialization positive feedback loops.
Let us begin by looking at the pollutants related to
mankind's increasing use of energy. The process of economic development
is in effect the process of utilizing more energy to increase the
productivity and efficiency of human labort In fact, one of the best
indications of the wealth of a human population is the amount of energy
it consumes per person (see figure 14). Per capita energy consumption in
the world is increasing at a rate of 1.3 percent per year,16 which
means a total increase, including population growth, of 3.4 percent per
year.
At present about 97 percent of mankind's industrial energy
production comes from fossil fuels (coal, oil, and natural gas).17 When
these fuels are burned, they release, among other
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substances, carbon dioxide (CO2) into the
atmosphere. Currently about 20 billion tons of CO2 are being released from fossil fuel combustion each
year.18 As figure 15 shows, the
measured amount of CO2 in the atmosphere is
increasing exponentially, apparently at a rate of about 0.2 percent per
year. Only about one half of the CO2 released
from burning fossil fuels has actually appeared in the
atmosphere—the other half has apparently been absorbed, mainly by
the surface water of the oceans.19
If man's energy needs are someday supplied by nuclear power
instead of fossil fuels, this increase in atmospheric CO2 will eventually cease, one hopes before it
has had any measurable ecological or climatological effect.
There is, however, another side–effect of energy use,
which is independent of the fuel source. By the laws of thermodynamics,
essentially all of the energy used by man must ultimately be dissapated
as heat. If the energy source is some thing other than incident solar
energy (e.g., fossil fuels or atomic energy), that heat will result in
warming the atmosphere, either directly, or indirectly through radiation
from water used for cooling purposes. Locally, waste heat or "thermal
pollution" in streams causes disruption in the balance of aquatic
life.20 Atmospheric waste heat
around cities causes the formation of urban "heat islands," within which
many meteorological anomalies occur.21
Thermal pollution may have serious climatic effects, worldwide, when it
reaches some appre–
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ciable fraction of the energy normally absorbed by the earth from the
sun.22 In figure 16, the level of thermal pollution
projected for one large city is shown as a fraction of incident solar
energy.
Nuclear power will produce yet another kind of pollutant
— radioactive wastes. Since nuclear power now provides only an
insignificant fraction of the energy used by man, the possible
environmental impact of the wastes released by nuclear reactors can only
be surmised. Some idea may be gained, however, by the actual and
expected releases of radioactive isotopes from the nuclear power plants
being built today. A partial list of the expected annual discharge to
the environment of a
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1.6 million kilowatt plant now under construction in the United States
includes 42,800 Curies*of radioactive krypton
*A Curie is the radioactive equivalent
of one gram of radium. This is such a large amount of radiation that
environmental concentrations are usually expressed in microcuries
(millionths of a Curie).
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(half-life ranging from a few hours to 9.4 years, depending on the
isotope) in the stack gases, and 2,910 Curies of tritium (half-life 12.5
years) in the waste water.23
Figure 17 shows how the nuclear generating capacity of the United States
is expected to grow from now until the year 2000. The graph also
includes an estimate of radioactive wastes annually released by these
nuclear power plants and of accumulated wastes (from spent reactor
fuels) that will have to be safely stored.
Carbon dioxide, thermal energy, and radioactive wastes are
just three of the many disturbances man is inserting into the
environment at an exponentially increasing rate. Other examples are
shown in figures 18-21.
Figure 18 shows the chemical changes occurring in a large
North American lake from accumulation of soluble industrial,
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agricultural, and municipal wastes. The accompanying decrease in
commercial fish production from the lake is also indicated. Figure 19
illustrates why the increase in organic wastes has such a catastrophic
effect on fish life. The figure shows the amount of dissolved oxygen
(which fish "breathe") in the Baltic Sea as a function of time. As
increasing amounts of wastes enter the water and decay, the dissolved
oxygen is depleted. In the case of some parts of the Baltic, the oxygen
level has actually reached zero.
The toxic metals lead and mercury are released into
waterways and into the atmosphere from automobiles, incinerators,
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industrial processes, and agricultural pesticides. Figure 20 shows the
exponential increase in mercury consumption in the United States from
1946 to 1968. Only 18 percent of this mercury is captured and recycled
after use.24 An exponential increase in
deposits of airborne lead has been detected by extraction of
successively deeper samples from the Greenland ice cap, as shown in
figure 21.
Unknown upper limits
All of these exponential curves of various kinds of pollution can be
extrapolated into the future, as we have extrapolated land needs in
figure 10 and resource use in figure 11. In both of
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these previous figures, the exponential growth curve eventually reached
an upper limit—the total amount of arable land or of resources
economically available in the earth. However, no upper bounds have been
indicated for the exponential growth curves of pollutants in figures
15–21, because it is not known how much we can perturb the natural
ecological balance of the earth without serious consequences. It is not
known how much CO2> or thermal pollution can
be released without causing irreversible changes in the earth's climate,
or how much radioactivity, lead, mercury, or pesticide can be absorbed
by plants, fish, or human beings before the vital processes are severely
interrupted.
Natural delays in ecological processes
This ignorance about the limits of the earth's ability to absorb
pollutants should be reason enough for caution in the release of
polluting substances. The danger of reaching those limits is especially
great because there is typically a long delay between the release of a
pollutant into the environment and the appearance of its negative effect
on the ecosysten. The dynamic implications of such a delayed effect can
be illustrated by the path of DDT through the environment after its use
as an insecticide. The results presented below are taken from a detailed
System Dynamics study* using the numerical
constants appropriate to DDT. The general conclusion is applicable (with
some change in the exact numbers involved) to all long-lived toxic
substances, such as mercury, lead, cadmium, other pesticides,
polychlorobiphenyl (PCB), and radioactive wastes.
*The study, by Jørgen Randers
and Dennis L. Meadows, is listed in the appendix.
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DDT is a man–made organic chemical released into the
environment as a pesticide at a rate of about 100,000 tons annually.25 After its
application by spraying, part of it evapporates and is carried long
distances in the air before it eventually precipitates back onto the
land or into the ocean. In the ocean some of the DDT is taken up by
plankton, some of the plankton are eaten by fish, and some of the fish
are finally eaten by man. At each step in the process the DDT may be
degraded into harmless substances, it may be release back into the
ocean, or it may be concentrated in the tissues of living organisms.
There is some time delay involved at each of these steps. All of these
steps. All these possible pathways have been analyzed by a computer to
produce the results seen in figure 22.
The DDT application rate shown in the figure follows the
world application rate from 1940 to 1970. The graph shows what would
happen if in 1970 the world DDT application rate began to decrease
gradually until it reached zero in the year 2000. Because of the
inherent delays in the system, the level of DDT in fish continues to
rise for more than 10 years after DDT use starts declining, and the
level in fish does not come back, down to the 1970
level until the year 1995—more than two decades after the
decision is made to reduce DDT application.
Whenever there is a long delay from the time of release of
a pollutant to the time of its appearance in a harmful form, we know
there will be an equally long delay from the time of control of that pollutant to the time when its harmful effect
finally decreases. In other words, any pollution control system based on
instituting controls only when some harm is already detected will
probably guarantee that the problem will get much worse before it gets
better. Systems of this sort are
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exceedingly difficult to control, because they require that present
actions be based on results expected far in the future.
Global distribution of pollutants
At the present time only the developed nations of the world are
seriously concerned about pollution. It is an unfortunate characteristic
of many types of pollution, however, that eventually they become widely
distributed around the world. Although Greenland is far removed from any
source of atmospheric lead pollution, the amount of lead deposited in
Greenland ice has increased 300 percent yearly since 1940.26 DDT has
accumulated in the body fat of humans in every part of the globe, from
Alaskan eskimos to city-dwellers of New Delhi, as shown in table 5.
Pollution Limits
Since pollution generation is a complicated function of population,
industrialization, and specific technological developments, it is
difficult to estimate exactly how fast the exponential curve of total
pollution release is rising. We might estimate that if the 7 billion
people of the year 2000 have a GNP per capita as high as that of
present–day Americans, the total pollution load on the environment
would be at least ten times its present value. Can the earth's natural
systems support an intrusion of that magnitude? We have no idea. Some
people believe that man has already so degraded the environment that
irreversible damage has been done to large natural systems. We do not
know the precise upper limit of the earth's ability to absorb any single
kind of pollution, much less its ability to absorb the combination of
all kinds of pollution. We do know however that there is an upper limit. It has already been surpassed in many local
environments. The surest way to
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Scroll Table to show more columns
Table 5 DDT IN BODY FAT
Population
Year
Number in sample
Concentration of
DDT and toxic
breakdown products
in body fat (parts per million)
Alaska (Eskimos)
1960
20
3.0
Canada
1959–60
62
4.9
England
1961–1962
131
2.2
England
1964
100
3.9
France
1961
10
5.2
Germany
1958–1959
60
2.3
Hungary
1960
48
12.4
India (Delhi)
1964
67
26.0
Israel
1963–1964
254
19.2
United States (Kentucky)
1942
10
.0
United States (Georgia, Kentucky, Arizona,
Washington)
1961–1962
130
12.7
United States (all areas
1964
64
7.6
Source:
Wayland J. Hayes, Jr., "Monitoring
Food and People for Pesticide Content," in Scientific Aspects of Pest Control
(Washington, DC: : National
Academy of Sciences—National Research Council.,
1966).
reach that upper limit globally is to increase exponentially both the
number of people and the polluting activities of each person.
The trade–offs involved in the environmental sector
of the world system are every bit as difficult to resolve as those in
the agricultural and natural resource sectors. The benefits of
pollution–generating activities are usually far removed in both
space and time from the costs. To make equitable decisions, therefore,
one must consider both space and time factors. If wastes are dumped
upstream, who will suffer downstream? If fungicides containing mercury
are used now, to what extent,
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when, and where will the mercury appear in ocean fish? If polluting
factories are located in remote areas to "isolate" the pollutants, where
will those pollutants be ten or twenty years from now?
It may be that technological developments will allow the
expansion of industry with decreasing pollution, but only at a high
cost. The US Council on Environmental Quality has called for an
expenditure of $105 billion between now and 1975 (42 percent of which is
to be paid by industry) for just a partial cleanup of American air,
water, and solid–waste pollution.27 Any
country can postpone the payment of such costs to increase the present
growth rate of its capital plant, but only at the expense of future
environmental degradation, which may be reversible only at very high
cost.
A FINITE WORLD
We have mentioned many difficult trade–offs in this chapter in the
production of food, in the consumption of resources, and in the generation
and clean–up of pollution. By now it should be clear that all of these
trade—offs arise from one simple fact—the earth is finite. The
closer any human activity comes to the limit of the earth's ability to
support that activity, the more apparent and unresolvable the
trade–offs become. When there is plenty of unused arable land, there
can be more people and also more food per person. When all the land is
already used, the trade–off between more people or more food per
person becomes a choice between absolutes.
In general, modern society has not learned to recognize and
deal with these trade–offs. The apparent goal of the present world
system is to produce more people with more (food, material goods, clean air
and water) for each person. In this
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chapter we have noted that if society continues to strive for that goal, it
will eventually reach one of many earthly limitations. As we shall see in
the next chapter, it is not possible to foretell exactly which limitation
will occur first or what the consequences will be, because there are many
conceivable, unpredictable human responses to such a situation. It is
possible, however, to investigate what conditions and what changes in the
world system might lead society to collision with or accommodation to the
limits to growth in a finite world.
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CHAPTER III GROWTH IN THE WORLD
SYSTEM
"In the circumference of a circle the beginning and end are common"
HERACLITUS, 500 B.C.
We have discussed food, nonrenewable resources, and
pollution absorption as separate factors necessary for the growth and
maintenance of population and industry. We have looked at the rate of growth in
the demand for each of these factors and at the possible upper limits to the
supply. By making simple extrapolations of the demand growth curves, we have
attempted to estimate, roughly, how much longer growth of each of these factors
might continue at its present rate of increase. Our conclusion from these
extrapolations is one that many perceptive people have already
realized—that the short doubling times of many of man's activities,
combined with the immense quantities being doubled, will bring us close to the
limits to growth of those activities surprisingly soon.
Extrapolation of present trends is a time–honored way of
looking into the future, especially the very near future, and especially if the
quantity being considered is not much in–
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fluenced by other trends that are occurring elsewhere in the system. Of course,
none of the five factors we are examining here is independent. Each interacts
constantly with all the others. We have already mentioned some of these
interactions. Population cannot grow without food, food production is increased
by growth of capital, more capital requires more resources, discarded resources
become pollution, pollution interferes with the growth of both population and
food.
Furthermore, over long time periods each of these factors also
feeds back to influence itself. The rate at which food production increases in
the 1970's, for example, will have some effect on the size of the population in
the 1980's, which will in turn determine the rate at which food production must
increase for many years thereafter. Similarly, the rate of resource consumption
in the next few years will influence both the size of the capital base that must
be maintained and the amount of resources left in the earth. Existing capital
and available resources will then interact to determine future resource supply
and demand.
The five basic quantities, or levels—population, capital,
food, nonrenewable resources, and pollution—are joined by still other
interrelationships and feedback loops that we have not yet discussed. Clearly it
is not possible to assess the long–term future of any of these levels
without taking all the others into account. Yet even this relatively simple
system has such a complicated structure that one cannot intuitively understand
how it will behave in the future, or how a change in one variable might
ultimately affect each of the others. To achieve such understanding, we must
extend our intuitive capabilities so that we can follow the complex,
interrelated behavior of many variables simultaneously.
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GROWTH IN THE WORLD SYSTEM
In this chapter we describe the formal world model that we have
used as a first step toward comprehending this complex world system. The model
is simply an attempt to bring together the large body of knowledge that already
exists about cause–and–effect relationships among the five levels
listed above and to express that knowledge in terms of interlocking feedback
loops. Since the world model is so important in understanding the causes of and
limits to growth in the world system, we shall explain the model–building
process in some detail.
In constructing the model, we followed four main steps:
1.We first listed the important causal relationships among the five
levels and traced the feedback loop structure. To do so we consulted
literature and professionals in many fields of study dealing with the areas
of concern—demography, economics, agronomy, nutrition, geology, and
ecology, for example. Our goal in this first step was to find the most basic
structure that would reflect the major interactions between the five levels.
We reasoned that elaborations on this basic structure, reflecting more
detailed knowledge, could be added after the simple system was understood.
2.We then quantified each relationship as accurately as possible,
using global data where it was available and characteristic local data where
global measurements had not been made.
3.With the computer, we calculated the simultaneous operation of all
these relationships over time. We then tested the effect of numerical
changes in the basic assumptions to find the most critical determinants of
the system's behavior.
4.Finally, we tested the effect on our global system of the
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GROWTH IN THE WORLD SYSTEM
various policies that are currently
being proposed to enhance or change the behavior of the system.
These steps were not necessarily followed serially, because often
new information coming from a later step would lead us back to alter the basic
feedback loop structure. There is not one inflexible world model; there is
instead an evolving model that is continuously criticized and updated as our own
understanding increases.
A summary of the present model, its purpose and limitations, the
most important feedback loops it contains, and our general procedure for
quantifying causal relationships follows.
THE PURPOSE OF THE WORLD MODEL
In this first simple world model, we are interested only in the broad
behavior modes of the population–capital system. By behavior modes we mean the tendencies of the variables in the
system (population or pollution, for example) to change as time progresses.
A variable may increase, decrease, remain constant, oscillate, or combine
several of these characteristic modes. For example, a population growing in
a limited environment can approach the ultimate carrying capacity of that
environment in several possible ways. It can adjust smoothly to an
equilibrium below the environmental limit by means of a gradual decrease in
growth rate, as shown below. It can over–
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GROWTH IN THE WORLD SYSTEM
shoot the limit and then die back again in either a smooth or an oscillatory
way, also as shown below. Or it can overshoot
the limit and in the process decrease the ultimate carrying capacity by
consuming some necessary nonrenewable resource, as diagramed below. This
behavior has been noted in many natural systems. For instance, deer or
goats, when natural enemies are absent, often overgraze their range and
cause erosion or destruction of the vegetation.28
A major purpose in constructing the world model has been to
determine which, if any, of these behavior modes will be most characteristic
of the world system as it reaches the limits to growth. This process of
determining behavior modes is "prediction" only in the most limited sense of
the word. The output graphs reproduced later in this book show values for
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world population, capital, and other variables on a time scale that begins
in the year 1900 and continues until 2100. These graphs are not exact predictions of the values of the variables
at any particular year in the future. They are indications of the system's
behavioral tendencies only.
The difference between the various degrees of "prediction"
might be best illustrated by a simple example. If you throw a ball straight
up into the air, you can predict with certainty what its general behavior
will be. It will rise with decreasing velocity, then reverse direction and
fall down with increasing velocity until it hits the ground. You know that
it will not continue rising forever, nor begin to orbit the earth, nor loop
three times before landing. It is this sort of elemental understanding of
behavior modes that we are seeking with the present world model. If one
wanted to predict exactly how high a thrown ball would rise or exactly where
and when it would hit the ground, it would be necessary to make a detailed
calculation based on precise information about the ball, the altitude, the
wind, and the force of the initial throw. Similarly, if we wanted to predict
the size of the earth's population in 1993 within a few percent, we would
need a very much more complicated model than the one described here. We
would also need information about the world system more precise and
comprehensive than is currently available.
Because we are interested at this point only in broad behavior
modes, this first world model need not be extremely detailed. We thus
consider only one general population, a population that statistically
reflects the average characteristics of the global population. We include
only one class of pollutants—the long–lived, globally
distributed family of pollutants, such as lead, mercury, asbestos, and
stable pesticides and radioisotopes—
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whose dynamic behavior in the ecosystem we are beginning to understand. We
plot one generalized resource that represents the combined reserves of all
nonrenewable resources, although we know that each separate resource will
follow the general dynamic pattern at its own specific level and rate.
This high level of aggregation is necessary at this point to
keep the model understandable. At the same time it limits the information we
can expect to gain from the model. Questions of detail cannot be answered
because the model simply does not yet contain much detail. National
boundaries are not recognized. Distribution inequalities of food, resources,
and capital are included implicitly in the data but they are not calculated
explicitly nor graphed in the output. World trade balances, migration
patterns, climatic determinants, and political processes are not
specifically treated. Other models can, and we hope will, be built to
clarify the behavior of these important subsystems.*
Can anything be learned from such a highly aggregated model?
Can its output be considered meaningful? In terms of exact predictions, the
output is not meaningful. We cannot forecast the precise population of the
United States nor the GNP of Brazil nor even the total world food production
for the year 2015. The data we have to work with are certainly not
sufficient for such forecasts, even if it were our purpose to make them. On
the other hand, it is vitally important to gain some understanding of the
causes of growth in human society, the limits to growth, and the behavior of
our socio–economic systems when the limits are reached. Man's
knowledge of the
*We have built numerous submodels
ourselves in the course of this study to investigate the detailed dynamics
underlying each sector of the world model. A list of those studies is
included in the appendix.
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behavior modes of these systems is very incomplete. It is currently not
known, for example, whether the human population will continue growing, or
gradually level off, or oscillate
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around some upper limit, or collapse. We believe that the aggregated world
model is one way to approach such questions. The model utilizes the most
basic relationships among people, food, investment, depreciation, resources,
output— relationships that are the same the world over, the same in
any part of human society or in society as a whole. In fact, as we indicated
at the beginning of this book, there are advantages to considering such
questions with as broad a space–time horizon as possible. Questions of
detail, of individual nations, and of short–term pressures can be
asked much more sensibly when the overall limits and behavior modes are
understood.
THE FEEDBACK LOOP STRUCTURE
In chapter I we drew a schematic representation of the feedback loops that
generate population growth and capital growth. They are reproduced together
in figure 23.
A review of the relationships diagramed in figure 23 may be
helpful. Each year the population is increased by the total number of births
and decreased by the total number of deaths that have taken place during
that year. The absolute number of births per year is a function of the
average fertility of the population and of the size of the population. The
number of deaths is related to the average mortality and the total
population size. As long as births exceed deaths, the population grows.
Similarly, a given amount of industrial capital, operating at constant
efficiency, will be able to produce a certain amount of output each year.
Some of that output will be more factories, machines, etc., which are
investments to increase the stock of capital goods. At the same time some
capital equipment will depreciate or be discarded each year. To keep
industrial capital growing, the investment rate must exceed the
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depreciation rate.
In all our flow diagrams, such as figure 23, the arrows simply
indicate that one variable has some influence on another. The nature and degree of
influence are not specified, although of course they must be quantified in
the model equations. For simplicity, we often omit noting in the flow
diagrams that several of the causal interactions occur only after a delay.
The delays are included explicitly in the model calculations.
Population and capital influence each other in many ways, some
of which are shown in figure 24. Some of the output of industrial capital is
agricultural capital—tractors, irrigation ditches, and fertilizers,
for example. The amount of agricultural capital and land area under
cultivation strongly influences the amount of food produced. The food per
capita (food produced divided by the population) influences the mortality of
the population. Both industrial and agricultural activity can cause
pollution. (In the case of agriculture, the pollution consists largely of
pesticide residues, fertilizers that cause eutrophication, and salt deposits
from improper irrigation.) Pollution may affect the mortality of the
population directly and also indirectly by decreasing agricultural
output.29
There are several important feedback loops in figure 24. If
everything else in the system remained the same, a population increase would decrease food per capita, and thus
increase mortality, increase the number of deaths, and eventually lead to a
population decrease. This negative feedback loop is diagramed below.
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Another negative feedback loop (shown below) tends to
counterbalance the one shown above. If the food per capita decreases to a value lower than that desired by the population,
there will be a tendency to increase agricultural capital, so that future
food production and food per capita can increase.
Other important relationships in the world model are
illustrated in figure 25. These relationships deal with population,
industrial capital, service capital, and resources.
Industrial output includes goods that are allocated to service
capital—houses, schools, hospitals, banks, and the equipment they
contain. The output from this service capital divided by the population
gives the average value of services per capita. Services per capita
influence the level of health services and thus the mortality of the
population. Services also include education and research into birth control
methods as well as distribution of birth control information and devices.
Services per capita are thus related to fertility.
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A changing industrial output per capita also has an observable
effect (though typically after a long delay) on many social factors that
influence fertility.
Each unit of industrial output consumes some nonrenewable
resource reserves. As the reserves gradually diminish, more capital is
necessary to extract the same amount of resource from the earth, and thus
the efficiency of capital decreases (that is, more capital is required to
produce a given amount of finished goods).
The important feedback loops in figure 25 are shown below.
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The relationships shown in figures 24 and 25 are typical of the
many interlocking feedback loops in the world model. Other loops include
such factors as the area of cultivated land and the rate at which it is
developed or eroded, the rate at which pollution is generated and rendered
harmless by the environment, and the balance between the labor force and the
number of jobs available. The complete flow diagram for the world model,
incorporating all these factors and more, is shown in figure 26.
QUANTITATIVE ASSUMPTIONS
Each of the arrows in figure 26 represents a general relationship that we
know is important or potentially important in the population–capital
system. The structure is, in fact, sufficiently general that it might also
represent a single nation or even a single city (with the addition of
migration and trade flows across boundaries). To apply the model structure
of figure 26 to a nation, we would quantify each relationship in the
structure with numbers characteristic of that nation. To represent the
world, the data would have to reflect average characteristics of the whole
world.
Most of the causal influences in the real world are nonlinear.
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That is, a certain change in a causal variable (such as an increase of 10
percent in food per capita) may affect another variable (life expectancy,
for example) differently, depending on the point within the possible range
of the second variable at which the change takes place. For instance, if an
increase in food per capita of 10 percent has been shown to increase life
expectancy by 10 years, it may not follow that an increase of food per
capita by 20 percent will increase life expectancy by 20 years. Figure 27
shows the nonlinearity of the relationship between food per capita and life
expectancy. If there is little food, a small increase may bring about a
large increase in life expectancy of a population. If there is already
sufficient food, a further increase will have little or no effect. Nonlinear
relationships of this sort have been incorporated directly into the world
model.*
The current state of knowledge about causal relationships in
the world ranges from complete ignorance to extreme accuracy. The
relationships in the world model generally fall in the middle ground of
certainty. We do know something about the direction and magnitude of the
causal effects, but we rarely have fully accurate information about them. To
illustrate how we operate on this intermediate ground of knowledge, we
present here three examples of quantitative relationships from the world
model. One is a relationship between economic variables that is relatively
well understood; another involves socio–psychological variables that
are well studied but difficult to quantify; and the third one relates
biological variables that
*The data in figure 27 have not been
corrected for variations in other factors, such as health care. Further
information on statistical treatment of such a relationship and on its
incorporation into the model equations will be presented in the technical
report.
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are, as yet, almost totally unknown. Although these three examples by no
means constitute a complete description of the world model, they illustrate
the reasoning we have used to construct and quantify it.
Per capita resource use
As the world's population and capital plant grow, what will happen to
the demand for nonrenewable resources? The amount of resources consumed
each year can be found by multiplying the population times the per
capita resource usage rate. Per capita resource usage rate is not
constant, of course. As a population becomes more wealthy, it tends to
consume more resources per person per year. The flow diagram expressing
the relationship of population, per capita resource usage rate, and
wealth (as measured by industrial output per capita) to the resource
usage rate is shown below.
The relationship between wealth (industrial output per
capita) and resource demand (per capita resource usage rate) is
expressed by a nonlinear curve of the form shown in figure 28. In figure
28 resource use is defined in terms of the world average resource
consumption per capita in 1970, which is set
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equal to 1. Since world average industrial output per capita in 1970 was
about $230,30 we know that the curve goes
through the point marked by an X. In 1970 the United States had an
average industrial output per capita of about $1,600, and the average
citizen consumed approximately seven times the world average per capita
resource usage.31 The point on the curve that
would represent the US level of consumption is marked by
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a +. We assume that, as the rest of the world develops economically, it
will follow basically the US pattern of consumption—a sharp upward
curve as output per capita grows, followed by a leveling off.
Justification for that assumption can be found in the present pattern of
world steel consumption (see figure 29). Although there is some
variation in the steel consumption curve from the general curve of
figure 28, the overall pattern is consistent, even given the differing
economic and political structures represented by the various nations.
Additional evidence for the general shape of the resource
consumption curve is shown by the history of US consumption of steel and
copper plotted in figure 30. As the average individual income has grown,
the resource usage in both cases has risen, at first steeply and then
less steeply. The final plateau represents an average saturation level
of material possessions. Further income increases are spent primarily on
services, which are less resource consuming.
The S-shaped curve of resource usage shown in figure 28 is
included in the world model only as a representation of apparent present policies. The curve can be altered at any
time in the model simulation to test the effects of system changes (such
as recycling of resources) that would either increase or decrease the
amount of nonrenewable resources each person consumes. Actual model runs
shown later in this book will illustrate the effects of such policies.
Desired birth rate
The number of births per year in any population equals the number of
women of reproductive age times the average fertility (the average
number of births per woman per year). There may be numerous factors
influencing the fertility of a
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population. In fact the study of fertility determinants is a major
occupation of many of the world's demographers. In the world model we
have identified three major components of fertility—maximum
biological birth rate, birth control effectiveness, and desired birth
rate. The relationship of these components to fertility is expressed in
the diagram below.
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The maximum biological birth rate is
the rate at which women would bear children if they practiced no method
of birth control throughout their entire reproductive lifetimes. This
rate is biologically determined, depending mainly on the general health
of the population. The desired birth rate is the
rate that would result if the population practiced "perfect"
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birth control and had only planned and wanted children. Birth control effectiveness measures the extent
to which the population is able to achieve the desired birth rate rather
than the maximum biological one. Thus "birth control" is defined very
broadly to include any method of controlling births actually practiced
by a population, including contraception, abortion, and sexual
abstinence. It should be emphasized that perfect birth control
effectiveness does not imply low fertility. If
desired birth rate is high, fertility will also be high.
These three factors influencing fertility are in turn
influenced by other factors in the world system. Figure 31 suggests that
industrialization might be one of the more important of these factors.
The relation between crude birth rates and GNP per capita
of all the nations in the world follows a surprisingly regular pattern.
In general, as GNP rises, the birth rate falls. This appears to be true,
despite differences in religious, cultural, or political factors. Of
course, we cannot conclude from this figure that a rising GNP per capita
directly causes a lower birth rate. Apparently, however, a number of
social and educational changes that ultimately lower the birth rate are
associated with increasing industrialization. These social changes
typically occur only after a rather long delay.
Where in the feedback loop structure does this inverse
relationship between birth rate and per capita GNP operate? Most
evidence would indicate that it does not operate through the maximum
biological birth rate. If anything, rising industrialization implies
better health, so that the number of births possible might increase as
GNP increases. On the other hand, birth control effectiveness would also
increase, and this effect certainly contributes to the decline in births
shown in figure 31.
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We suggest, however, that the major effect of rising GNP is on the desired birth rate. Evidence for this suggestion
is shown in figure 32. The curve indicates the percentage of respondents
to family planning surveys wanting more than four children as a function
of GNP per capita. The general shape of the curve is similar to that of
figure 31, except for the slight increase in desired family size at high
incomes.
The economist J. J. Spengler has explained the general response of
desired birth rate to income in terms of the economic and social changes
that occur during the process of
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industrialization.32 He believes that each
family, consciously or unconsciously, weighs the value and cost of an
additional child against the resources the family has available to
devote to that child. This process results in a general attitude about
family size that shifts as income increases, as shown in figure 33.
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The "value" of a child includes monetary considerations,
such as the child's labor contribution to the family farm or business
and the eventual dependence on the child's support when the parents
reach old age. As a country becomes industrialized, child labor laws,
compulsory education, and social security provisions all reduce the
potential monetary value of a child. "Value" also includes the more
intangible values of a child as an object of love, a carrier of the
family name, an inheritor of the family property, and a proof of
masculinity. These values tend to be important in any society, and so
the reward function always has a positive value. It is particularly
important in poor societies, where there are almost no alternative modes
of personal gratification.
The "cost" of a child includes the actual financial outlays
necessary to supply the child's needs, the opportunity costs of the
mother's time devoted to child care, and the increased responsibility
and decreased freedom of the family as a whole. The cost of children is
very low in a traditional society. No additional living space is added
to house a new child, little education or medical care is available,
clothing and food requirements are minimal. The mother is generally
uneducated and assigns no value to her time. The family has little
freedom to do anything that a child would hinder, and the extended
family structure is there to provide child care if it should become
necessary, for example, for a parent to leave home to find a job.
As family income increases, however, children are given
more than the basic food and clothing requirements. They receive better
housing and medical care, and education becomes both necessary and
expensive. Travel, recreation, and alternative employment for the mother
become possibilities that are
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not compatible with a large family. The extended family structure tends
to disappear with industrialization, and substitute child care is
costly.
The "resources" that a family has to devote to a child
generally increase with income. At very high income, the value and cost
curves become nearly invariant with further increases in income, and the
resource curve becomes the dominant factor in the composite desired
birth rate. Thus, in rich countries, such as the United States, desired
family size becomes a direct function of income. It should be noted that
"resources" is partially a psychological concept in that present actual
income must be modified by an expectation of future income in planning
family size.
We have summarized all these social factors by a feedback
loop link between industrial output per capita and desired birth rate.
The general shape of the relationship is shown on the right side of
figure 33. We do not mean to imply by this link that rising income is
the only determinant of desired family size, or even that it is a direct
determinant. In fact we include a delay between industrial output per
capita and desired family size to indicate that this relationship
requires a social adjustment, which may take a generation or two to
complete. Again, this relationship may be altered by future policies or
social changes. As it stands it simply reflects the historical behavior
of human society. Wherever economic development has taken place, birth
rates have fallen. Where industrialization has not occurred, birth rates
have remained high.
Pollution effect on lifetime
We have included in the world model the possibility that
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pollution will influence the life expectancy of the world's population.
We express this relationship by a "lifetime multiplier from pollution,"
a function that multiplies the life expectancy otherwise indicated (from
the values of food and medical services) by the contribution to be
expected from pollution. If pollution were severe enough to lower the
life expectancy to 90 percent of its value in the absence of pollution,
the multiplier would equal 0.9. The relationship of pollution to life
expectancy is diagramed below.
There are only meager global data on the effect of
pollution on life expectancy. Information is slowly becoming available
about the toxicity to humans of specific pollutants, such as mercury and
lead. Attempts to relate statistically a given concentration of
pollutant to the mortality of a population have been made only in the
field of air pollution.33
Although quantitative evidence is not yet available, there
is little doubt that a relationship does indeed exist between pollution
and human health. According to a recent Council on Environmental Quality
report:
Serious air pollution episodes have demonstrated how air pollution can
severely impair health. Further research is spawning a growing body of
evidence which indicates that even the long–term effects of
exposure to low concentrations of pollutants can damage health and cause
chronic disease and premature death, especially for the most
vulnerable—the aged and those already suffering from respiratory
diseases. Major illnesses linked to air pollution include emphysema,
bronchitis, asthma, and lung cancer.34
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What will be the effect on human lifetime as the present
level of global pollution increases? We cannot answer this question
accurately, but we do know that there will be
some effect. We would be more in error to ignore the influence
of pollution on life expectancy in the world model than to include it
with our best guess of its magnitude. Our approach to a "best guess" is
explained below and illustrated in figure 34.
If an increase in pollution by a factor of 100 times the
present global level would have absolutely no effect on lifetime, the
straight line A in figure 34 would be the correct representation of the
relationship we seek. Life expectancy would be unrelated to pollution.
Curve A is very unlikely, of course, since we know that many forms of
pollution are damaging to the human body. Curve B or any similar curve
that rises above curve A is even more unlikely since it indicates that
additional pollution will increase average lifetime. We can expect that
the relationship between pollution and lifetime is negative, although we
do not know what the exact shape or slope of a curve expressing it will
be. Any one of the curves labeled C, or any other negative curve, might
represent the correct function.
Our procedure in a case like this is to make several
different estimates of the probable effect of one variable on another
and then to test each estimate in the model. If the model behavior is
very sensitive to small changes in a curve, we know we must obtain more
information before including it. If (as in this case) the behavior mode
of the entire model is not substantially altered by changes in the
curve, we make a conservative guess of its shape and include the
corresponding values in our calculation. Curve C" in figure 34 is the
one we believe most accurately depicts the relationship between life
expectancy
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and pollution. This curve assumes that an increase in global pollution
by a factor of 10 would have almost no effect on lifetime but an
increase by a factor of 100 would have a great effect.
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The usefulness of the world model
The relationships discussed above comprise only three of the hundred or
so causal links that make up the world model. They have been chosen for
presentation here as examples of the kind of information inputs we have
used and the way in which we have used them. In many cases the
information available is not complete. Nevertheless, we believe that the
model based on this information is useful even at this preliminary stage
for several reasons.
First, we hope that by posing each relationship as a
hypothesis, and emphasizing its importance in the total world system, we
may generate discussion and research that will eventually improve the
data we have to work with. This emphasis is especially important in the
areas in which different sectors of the model interact (such as
pollution and human lifetime), where interdisciplinary research will be
necessary.
Second, even in the absence of improved data, information
now available is sufficient to generate valid basic behavior modes for
the world system. This is true because the model's feedback loop
structure is a much more important determinant of overall behavior than
the exact numbers used to quantify the feedback loops. Even rather large
changes in input data do not generally alter the mode of behavior, as we shall see in the following pages.
Numerical changes may well affect the period of
an oscillation or the rate of growth or the time of a collapse, but they will not affect the
fact that the basic mode is oscillation or growth or collapse.* Since we intend to use the
*The importance of structure rather
than numbers is a most difficult concept to present without extensive
examples from the observation and modeling of dynamic systems. For
further discussion of this point, see chapter 6 of J. W.
Forrester's Urban Dynamics
(Cambridge, Mass.: : MIT
Press., 1969).
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world model only to answer questions about behavior modes, not to make
exact predictions, we are primarily concerned with the correctness of
the feedback loop structure and only secondarily with the accuracy of
the data. Of course when we do begin to seek more detailed, short-term
knowledge, exact numbers will become much more important.
Third, if decision–makers at any level had access to
precise predictions and scientifically correct analyses of alternate
policies, we would certainly not bother to construct or publish a
simulation model based on partial knowledge. Unfortunately, there is no
perfect model available for use in evaluating today's important policy
issues. At the moment, our only alternatives to a model like this, based
on partial knowledge, are mental models, based on the mixture of
incomplete information and intuition that currently lies behind most
political decisions. A dynamic model deals with the same incomplete
information available to an intuitive model, but it allows the
organization of information from many different sources into a feedback
loop structure that can be exactly analyzed. Once all the assumptions
are together and written down, they can be exposed to criticism, and the
system's response to alternative policies can be tested.
WORLD MODEL BEHAVIOR
Now we are at last in a position to consider seriously the questions we
raised at the beginning of this chapter. As the world system grows toward
its ultimate limits, what will be its most likely behavior mode? What
relationships now existent will change as the exponential growth curves
level off? What will the world be like when growth comes to an end?
There are, of course, many possible answers to these
ques–
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tions. We will examine several alternatives, each dependent on a different
set of assumptions about how human society will respond to problems arising
from the various limits to growth.
Let us begin by assuming that there will be in the future no
great changes in human values nor in the functioning of the global
population–capital system as it has operated for the last one hundred
years. The results of this assumption are shown in figure 35. We shall refer
to this computer output as the "standard run" and use it for comparison with
the runs based on other assumptions that follow. The horizontal scale in
figure 35 shows time in years from 1900 to 2100. With the computer we have
plotted the progress over time of eight quantities:
Each of these variables is plotted on a different vertical
scale. We have deliberately omitted the vertical scales and we have made the
horizontal time scale somewhat vague because we want to emphasize the
general behavior modes of these computer outputs, not the numerical values,
which are only approxi–
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mately known. The scales are, however, exactly equal in all the computer
runs presented here, so results of different runs may be easily compared.
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All levels in the model (population, capital, pollution, etc.)
begin with 1900 values. From 1900 to 1970 the variables plotted in figure 35
(and numerous other variables included in the model but not plotted here)
agree generally with their historical values to the extent that we know
them. Population rises from 1.6 billion in 1900 to 3.5 billion in 1970.
Although the birth rate declines gradually, the death rate falls more
quickly, especially after 1940, and the rate of population growth increases.
Industrial output, food, and services per capita increase exponentially. The
resource base in 1970 is still about 95 percent of its 1900 value, but it
declines dramatically thereafter, as population and industrial output
continue to grow.
The behavior mode of the system shown in figure 35 is clearly
that of overshoot and collapse. In this run the collapse occurs because of
nonrenewable resource depletion. The industrial capital stock grows to a
level that requires an enormous input of resources. In the very process of
that growth it depletes a large fraction of the resource reserves available.
As resource prices rise and mines are depleted, more and more capital must
be used for obtaining resources, leaving less to be invested for future
growth. Finally investment cannot keep up with depreciation, and the
industrial base collapses, taking with it the service and agricultural
systems, which have become dependent on industrial inputs (such as
fertilizers, pesticides, hospital laboratories, computers, and especially
energy for mechanization). For a short time the situation is especially
serious because population, with the delays inherent in the age structure
and the process of social adjustment, keeps rising. Population finally
decreases when the death rate is driven upward by lack of food and health
services.
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The exact timing of these events is not meaningful, given the
great aggregation and many uncertainties in the model. It is significant,
however, that growth is stopped well before the year 2100. We have tried in
every doubtful case to make the most optimistic estimate of unknown
quantities, and we have also ignored discontinuous events such as wars or
epidemics, which might act to bring an end to growth even sooner than our
model would indicate. In other words, the model is biased to allow growth to
continue longer than it probably can continue in the real world. We can thus say with some confidence that, under the
assumption of no major change in the present system, population and
industrial growth will certainly stop within the next century, at the
latest.
The system shown in figure 35 collapses because of a resource
crisis. What if our estimate of the global stock of resources is wrong? In
figure 35 we assumed that in 1970 there was a 250–year supply of all
resources, at 1970 usage rates. The static reserve index column of the
resource table in chapter II will verify that this assumption is indeed
optimistic. But let us be even more optimistic and assume that new
discoveries or advances in technology can double the
amount of resources economically available. A computer run under that
assumption is shown in figure 36.
The overall behavior mode in figure 36—growth and
collapse—is very similar to that in the standard run. In this case the
primary force that stops growth is a sudden increase in the level of
pollution, caused by an overloading of the natural absorptive capacity of
the environment. The death rate rises abruptly from pollution and from lack
of food. At the same time resources are severely depleted, in spite of the
doubled amount available, simply because a few more years of expo–
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nential growth in industry are sufficient to consume those extra resources.
Is the future of the world system bound to be growth and then
collapse into a dismal, depleted existence? Only if we
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make the initial assumption that our present way of doing things will not
change. We have ample evidence of mankind's ingenuity and social
flexibility. There are, of course, many likely changes in the system, some
of which are already taking place. The Green Revolution is raising
agricultural yields in nonindustrialized countries. Knowledge about modern
methods of birth control is spreading rapidly. Let us use the world model as
a tool to test the possible consequences of the new technologies that
promise to raise the limits to growth.
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CHAPTER IV TECHNOLOGY AND THE
LIMITS TO GROWTH
"Towards what ultimate point is society tending by its industrial
progress? When the progress ceases, in what condition are we to expect that
it will leave mankind?"
JOHN STUART MILL, 1857
Although the history of human effort contains numerous
incidents of mankind's failure to live within physical limits, it is success in
overcoming limits that forms the cultural tradition of many dominant people in
today's world. Over the past three hundred years, mankind has compiled an
impressive record of pushing back the apparent limits to population and economic
growth by a series of spectacular technological advances. Since the recent
history of a large part of human society has been so continuously successful, it
is quite natural that many people expect technological breakthroughs to go on
raising physical ceilings indefinitely. These people speak about the future with
resounding technological optimism.
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There are no substantial limits in sight either in raw materials or in energy
that alterations in the price structure, product substitution, anticipated gains
in technology and pollution control cannot be expected to solve.35
Given the present capacity of the earth for food production, and the potential
for additional food production if modern technology were more fully employed,
the human race clearly has within its grasp the capacity to chase hunger from
the earth—within a matter of a decade or two.36
Humanity's mastery of vast, inanimate, inexhaustible energy sources and the
accelerated doing more with less of sea, air, and space technology has proven
Malthus to be wrong. Comprehensive physical and economic success for humanity
may now be accomplished in one-fourth of a century.37
Can statements like these be reconciled with the evidence for the
limits to growth we have discussed here ? Will new technologies alter the
tendency of the world system to grow and collapse? Before accepting or rejecting
these optimistic views of a future based on technological solutions to mankind's
problems, one would like to know more about the global impact of new
technologies, in the short term and the long term, and in all five interlocking
sectors of the population-capital system.
TECHNOLOGY IN THE WORLD MODEL
There is no single variable called "technology" in the world model. We have
not found it possible to aggregate and generalize the dynamic implications
of technological development because different technologies arise from and
influence quite different sectors of the model. Birth control pills,
high-yield grains, television, and off–shore oil–drilling rigs
can all be considered technological developments, but each plays a distinct
role in altering the behavior of the world system. There–
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fore we must represent each proposed technology separately in the model,
considering carefully how it might affect each of the assumptions we have
made about the model elements. In this section we shall present some
examples of this approach to global, long–term "technology
assessment."
Energy and resources
The technology of controlled nuclear fission has already lifted the
impending limit of fossil fuel resources. It is also possible that the
advent of fast breeder reactors and perhaps even fusion nuclear reactors
will considerably extend the lifetime of fissionable fuels, such as
uranium. Does this mean that man has mastered "vast, inanimate,
inexhaustible energy sources" that will release unlimited raw materials
for his industrial plants? What will be the effect of increasing use of
nuclear power on resource availability in the world system?
Some experts believe that abundant energy resources will
enable mankind to discover and utilize otherwise inaccessible materials
(in the sea bed, for example); to process poorer ores, even down to
common rock; and to recycle solid waste and reclaim the metals it
contains. Although this is a common belief, it is by no means a
universal one, as the following quotation by geologist Thomas Lovering
indicates.
Cheaper energy, in
fact, would little reduce the total costs (chiefly capital and labor)
required for mining and processing rock. The enormous quantities of
unusable waste produced for each unit of metal in ordinary granite (in a
ratio of at least 2,000 to 1) are more easily disposed of on a blueprint
than in the field. ... To recover minerals sought, the rock must be
shattered by explosives, drilled for input and recovery wells, and
flooded with solutions containing special extractive chemicals.
Provision must then be made to avoid the loss of solutions and the
consequent contamination of groundwater and surface water. These
operations will not be obviated by nuclear power.38
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Let us assume, however, that the technological optimists
are correct and that nuclear energy will solve the resource problems of
the world. The result of including that assumption in the world model is
shown in figure 37. To express the possibility of utilizing lower grade
ore or mining the seabed, we have doubled the total amount of resources
available, as in
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figure 36. We have also assumed that, starting in 1975, programs of
reclamation and recycling will reduce the input of virgin resources
needed per unit of industrial output to only one-fourth of the amount
used today. Both of these assumptions are, admittedly, more optimistic
than realistic.
In figure 37 resource shortages indeed do not occur.
Growth is stopped by rising pollution, as it was in figure 36. The
absence of any constraint from resources allows industrial output, food,
and services to rise slightly higher than in figure 36 before they fall.
Population reaches about the same peak level as it did in figure 36, but
it falls more suddenly and to a lower final value.
"Unlimited" resources thus do not appear to be the key to
sustaining growth in the world system. Apparently the economic impetus
such resource availability provides must be accompanied by curbs on
pollution if a collapse of the world system is to be avoided.
Pollution control
We assumed in figure 37 that the advent of nuclear power neither
increased nor decreased the average amount of pollution generated per
unit of industrial output. The ecological impact of nuclear power is not
yet clear. While some by–products of fossil fuel consumption, such
as CO2 and sulfur dioxide, will be decreased,
radioactive by–products will be increased. Resource recycling will
certainly decrease pollution from solid waste and from some toxic
metals. However, a changeover to nuclear power will probably have little
effect on most other kinds of pollution, including by–products of
most manufacturing processes, thermal pollution, and pollution arising
from agricultural practices.
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It is likely, however, that a world society with readily
available nuclear power would be able to control industrial pollution
generation by technological means. Pollution control devices are already
being developed and installed on a large scale in industrialized areas.
How would the model behavior
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be changed if a policy of strict pollution control were instituted in,
say, 1975?
Strict pollution control does not necessarily mean total pollution control. It is impossible to
eliminate all pollution because of both technological and economic
constraints. Economically, the cost of pollution control soars as
emission standards become more severe. Figure 38 shows the cost of
reducing water pollution from a sugar–processing plant as a
function of organic wastes removed. If no organic
wastes were allowed to leave the plant, the cost would be 100 times
greater than if only 30 percent of the wastes were removed from the
effluent. Table 6 below shows a similar trend in the projected costs of
reducing air pollution in a US city.39
In figure 39 the world model output is plotted assuming
both the reduction in resource depletion of
figure 37 and a reduction in pollution generation
from all sources by a factor of four,
Scroll Table to show more columns
Table 6 COST OF REDUCING AIR POLLUTION IN A US CITY
Percent reduction in SO2
Percent reduction in particulates
Projected cost
5
22
$50,000
42
66
7,500,000
48
69
26,000,000
starting in 1975. Reduction to less than one–fourth of the present
rate of pollution generation is probably unrealistic because of cost,
and because of the difficulty of eliminating some kinds (of pollution,
such as thermal pollution and radioisotopes from nuclear power
generation, fertilizer runoff, and asbestos particles from brake
linings. We assume that such a sharp reduc–
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TECHNOLOGY AND THE LIMITS TO GROWTH
tion in pollution generation could occur globally and quickly for
purposes of experimentation with the model, not because we believe it is
politically feasible, given our present institutions.
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TECHNOLOGY AND THE LIMITS TO GROWTH
As figure 39 shows, the pollution control policy is indeed
successful in averting the pollution crisis of the previous run. Both
population and industrial output per person rise well beyond their peak
values in figure 37, and yet resource depletion and pollution never
become problems. The overshoot mode is still operative, however, and the
collapse comes about this time from food shortage.
As long as industrial output is rising in figure 39, the
yield from each hectare of land continues to rise (up to a maximum of
seven times the average yield in 1900) and new land is developed. At the
same time, however, some arable land is taken for urban-industrial use,
and some land is eroded, especially by highly capitalized agricultural
practices. Eventually the limit of arable land is reached. After that
point, as population continues to rise, food per capita decreases. As
the food shortage becomes apparent, industrial output is diverted into
agricultural capital to increase land yields. Less capital is available
for investment, and finally the industrial output per capita begins to
fall. When food per capita sinks to the subsistence level, the death
rate begins to increase, bringing an end to population growth.
Increased food yield and birth control
The problem in figure 39 could be viewed either as too little food or as
too many people. The technological response to the first situation would
be to produce more food, perhaps by some further extension of the
principles of the Green Revolution. (The development of the new,
high–yield grain varieties which constitutes the Green Revolution
has been included in the original model equations.) The technological
solution to the second problem would be to provide better methods of
birth
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TECHNOLOGY AND THE LIMITS TO GROWTH
control. The results of these two changes, instituted in 1975 along with
the changes in resource use and pollution generation we have already
discussed, are shown both separately and simultaneously in figures 40,
41, and 42.
In figure 40 we assume that the normal yield per hectare
of
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all the world's land can be further increased by a factor of two. The
result is an enormous increase in food, industrial output, and services
per capita. Average industrial output per person for all the world's
people becomes nearly equal to the 1970 US level, but only briefly.
Although a strict pollution control policy is still in effect, so that
pollution per unit of output is
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reduced by a factor of four, industry grows so quickly that soon it is
producing four times as much output. Thus the level of pollution rises
in spite of the pollution control policy, and a
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pollution crisis stops further growth, as it did in figure 37.
Figure 41 shows the alternate technological
policy—perfect birth control, practiced voluntarily, starting in
1975. The result is not to stop population growth entirely because such
a policy prevents only the births of unwanted
children. The birth rate does decrease markedly, however, and the
population grows more slowly than it did in figures 39 and 40. In this
run growth is stopped by a food crisis occurring about 20 years later
than in figure 39.
In figure 42 we apply increased land yield and perfect
birth control simultaneously. Here we are utilizing a technological
policy in every sector of the world model to circumvent in some way the
various limits to growth. The model system is producing nuclear power,
recycling resources, and mining the most remote reserves; withholding as
many pollutants as possible; pushing yields from the land to
undreamed–of heights; and producing only children who are actively
wanted by their parents. The result is still an end to growth before the
year 2100. In this case growth is stopped by three simultaneous crises.
Overuse of land leads to erosion, and food production drops. Resources
are severely depleted by a prosperous world population (but not as
prosperous as the present US population). Pollution rises, drops, and
then rises again dramatically, causing a further decrease in food
production and a sudden rise in the death rate. The application of
technological solutions alone has prolonged the period of population and
industrial growth, but it has not removed the ultimate limits to that
growth.
The overshoot mode
Given the many approximations and limitations of the world model, there
is no point in dwelling glumly on the series of
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catastrophes it tends to generate. We shall emphasize just one more time
that none of these computer outputs is a prediction. We would not expect
the real world to behave like the world model in any of the graphs we
have shown, especially in the collapse modes. The model contains dynamic
statements about only the physical aspects of man's activities. It
assumes that social variables—income distribution, attitudes about
family size, choices among goods, services, and food—will continue
to follow the same patterns they have followed throughout the world in
recent history. These patterns, and the human values they represent,
were all established in the growth phase of our civilization. They would
certainly be greatly revised as population and income began to decrease.
Since we find it difficult to imagine what new forms of human societal
behavior might emerge and how quickly they would emerge under collapse
conditions, we have not attempted to model such social changes. What
validity our model has holds up only to the point in each output graph
at which growth comes to an end and collapse begins.
Although we have many reservations about the
approximations and simplifications in the present world model, it has
led us to one conclusion that appears to be justified under all the
assumptions we have tested so far. The basic behavior
mode of the world system is exponential growth of population and
capital, followed by collapse. As we have shown in the model
runs presented here, this behavior mode occurs if we assume no change in
the present system or if we assume any number of technological changes
in the system.
The unspoken assumption behind all of the model runs we
have presented in this chapter is that population and capital growth
should be allowed to continue until they reach some
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"natural" limit. This assumption also appears to be a basic part of the
human value system currently operational in the real world. Whenever we
incorporate this value into the model, the result is that the growing
system rises above its ultimate limit and then collapses. When we
introduce technological developments that successfully lift some
restraint to growth or avoid some collapse, the system simply grows to
another limit, temporarily surpasses it, and falls back. Given that
first assumption, that population and capital growth should not be
deliberately limited but should be left to "seek their own levels," we
have not been able to find a set of policies that avoids the collapse
mode of behavior.
It is not really difficult to understand how the collapse
mode comes about. Everywhere in the web of interlocking feedback loops
that constitutes the world system we have found it necessary to
represent the real–world situation by introducing time delays
between causes and their ultimate effects. These are natural delays that
cannot be controlled by technological means. They include, for example,
the delay of about fifteen years between the birth of a baby and the
time that baby can first reproduce itself. The time delay inherent in
the aging of a population introduces a certain unavoidable lag in the
ability of the population to respond through the birth rate to changing
conditions. Another delay occurs between the time a pollutant is
released into the environment and the time it has a measurable influence
on human health. This delay includes the passage of the pollutant
through air or rivers or soil and into the food chain, and also the time
from human ingestion or absorption of the pollutant until clinical
symptoms appear. This second delay may be as long as 20 years in the
case of some carcinogens. Other delays occur because capital cannot
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be transferred instantly from one sector to another to meet changing
demands, because new capital and land can only be produced or developed
gradually, and because pollution can only slowly be dispersed or
metabolized into harmless forms.
Delays in a dynamic system have serious effects only if
the system itself is undergoing rapid changes. Perhaps a simple example
will clarify that statement. When you drive a car there is a very short,
unavoidable delay between your perception of the road in front of you
and your reaction to it. There is a longer delay between your action on
the accelerator or brakes and the car's response to that action. You
have learned to deal with those delays. You know that, because of the
delays, it is unsafe to drive too fast. If you do, you will certainly
experience the overshoot and collapse mode, sooner or later. If you were
blindfolded and had to drive on the instructions of a front–seat
passenger, the delay between perception and action would be considerably
lengthened. The only safe way to handle the extended delay would be to
slow down. If you tried to drive your normal speed, or if you tried to
accelerate continuously (as in exponential growth), the result would be
disastrous.
In exactly the same way, the delays in the feedback loops
of the world system would be no problem if the system were growing very
slowly or not at all. Under those conditions any new action or policy
could be instituted gradually, and the changes could work their way
through the delays to feed back on every part of the system before some
other action or policy would have to be introduced. Under conditions of
rapid growth, however, the system is forced into new policies and
actions long before the results of old policies and actions can be
properly assessed. The situation is even worse when the
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growth is exponential and the system is changing ever more rapidly.
Thus population and capital, driven by exponential growth,
not only reach their limits, but temporarily shoot beyond them before
the rest of the system, with its inherent delays, reacts to stop growth.
Pollution generated in exponentially increasing amounts can rise past
the danger point, because the danger point is first perceived years
after the offending pollution was released. A rapidly growing industrial
system can build up a capital base dependent on a given resource and
then discover that the exponentially shrinking resource reserves cannot
support it. Because of delays in the age structure, a population will
continue to grow for as long as 70 years, even after average fertility
has dropped below the replacement level (an average of two children for
each married couple).
TECHNOLOGY IN THE REAL WORLD
The hopes of the technological optimists center on the ability of technology
to remove or extend the limits to growth of population and capital. We have
shown that in the world model the application of technology to apparent
problems of resource depletion or pollution or food shortage has no impact
on the essential problem, which is exponential growth
in a finite and complex system. Our attempts to use even the most optimistic
estimates of the benefits of technology in the model did not prevent the
ultimate decline of population and industry, and in fact did not in any case
postpone the collapse beyond the year 2100. Before we go on in the next
chapter to test other policies, which are not technological, let us extend
our discussion of technological solutions to some aspects of technology that
could not be included in the world model.
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Technological side-effects
Dr. Garrett Hardin has defined side-effects as "effects which I hadn't
foreseen or don't want to think about."40 He
has suggested that, since such effects are actually inseparable from the
principal effect, they should not be labeled side–effects at all. Every new technology has
side–effects, of course, and one of the main purposes of
model–building is to anticipate those effects. The model runs in
this chapter have shown some of the side–effects of various
technologies on the world's physical and economic systems. Unfortunately
the model does not indicate, at this stage, the social side–effects of new technologies. These effects
are often the most important in terms of the influence of a technology
on people's lives.
A recent example of social side-effects from a successful
new technology appeared as the Green Revolution was introduced to the
agrarian societies of the world. The Green Revolution— the
utilization of new seed varieties, combined with fertilizers and
pesticides—was designed to be a technological solution to the
world's food problems. The planners of this new agricultural technology
foresaw some of the social problems it might raise in traditional
cultures. The Green Revolution was intended not only to produce more
food but to be labor–intensive —to provide jobs and not to
require large amounts of capital. In some areas of the world, such as
the Indian Punjab, the Green Revolution has indeed increased the number
of agricultural jobs faster than the rate of growth of the total
population. In the East Punjab there was a real wage increase of 16
percent from 1963 to 1968.41
The principal, or intended, effect of the Green
Revolution—increased food production—seems to have been
achieved. Unfortunately the social side-effects have not been entirely
bene–
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ficial in most regions where the new seed varieties have been
introduced. The Indian Punjab had, before the Green Revolution, a
remarkably equitable system of land distribution. The more common
pattern in the nonindustrialized world is a wide range in land
ownership, with most people working very small farms and a few people in
possession of the vast majority of the land.
Where these conditions of economic inequality already
exist, the Green Revolution tends to cause widening inequality. Large
farmers generally adopt the new methods first. They have the capital to
do so and can afford to take the risk. Although the new seed varieties
do not require tractor mechanization, they provide much economic
incentive for mechanization, especially where multiple cropping requires
a quick harvest and replanting. On large farms, simple economic
considerations lead almost inevitably to the use of
labor–displacing machinery and to the purchase of still more
land.42 The ultimate effects of this
socio–economic positive feedback loop are agricultural
unemployment, increased migration to the city, and perhaps even
increased malnutrition, since the poor and unemployed do not have the
means to buy the newly produced food.
A specific example of the social side-effects of the Green
Revolution in an area where land is unequally distributed is described
below.
Statistics from Mexico, where the Green Revolution
began
A landless
laborer's income in West Pakistan today is still just about what it was
five years ago, less than $100 a year. In contrast, one landlord with a
1,500-acre wheat farm told me when I was in Pakistan this winter that he
had cleared a net profit of more than $100,000 on his last harvest.43
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in the 1940's, provide another example. From 1940 to 1960 the average
growth rate of agricultural production in Mexico was 5 percent per year.
From 1950 to I960, however, the average number of days worked by a
landless laborer fell from 194 to 100, and his real income decreased
from $68 to $56. Eighty percent of the increased agricultural production
came from only 3 percent of the farms.44
These unexpected social side–effects do not imply
that the technology of the Green Revolution was unsuccessful. They do
imply that social side–effects must be anticipated and forestalled
before the large-scale introduction of a new
technology.
Such preparation for technological change requires, at the
very least, a great deal of time. Every change in the normal way of
doing things requires an adjustment time, while the population,
consciously or unconsciously, restructures its social system to
accommodate the change. While technology can change rapidly, political
and social institutions generally change very slowly. Furthermore, they
almost never change in anticipation of a social
need, but only in response to one.
We have already mentioned the dynamic effect of physical
delays in the world model. We must also keep in mind the presence of
social delays—the delays necessary to allow society to absorb or
to prepare for a change. Most delays, physical or social, reduce the
stability of the world system and increase
As agriculture
emerges from its traditional subsistence state to modern commercial
farming ... it becomes progressively more important to ensure that
adequate rewards accrue directly to the man who tills the soil. Indeed,
it is hard to see how there can be any meaningful modernization of food
production in Latin America and Africa south of the Sahara unless land
is registered, deeded, and distributed more equitably.45
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the likelihood of the overshoot mode. The social delays, like the
physical ones, are becoming increasingly more critical because the
processes of exponential growth are creating additional pressures at a
faster and faster rate. The world population grew from 1 billion to 2
billion over a period of more than one hundred years. The third billion
was added in 30 years and the world's population has had less than 20
years to prepare for its fourth billion. The fifth, sixth, and perhaps
even seventh billions may arrive before the year 2000, less than 30
years from now. Although the rate of technological change has so far
managed to keep up with this accelerated pace, mankind has made
virtually no new discoveries to increase the rate of social (political,
ethical, and cultural) change.
Problems with no technical solutions
When the cities of America were new, they grew rapidly. Land was
abundant and cheap, new buildings rose continuously, and the population
and economic output of urban regions increased. Eventually, however, all
the land in the city center was filled. A physical limit had been
reached, threatening to stop population and economic growth in that
section of the city. The technological answer was the development of
skyscrapers and elevators, which essentially removed the constraint of
land area as a factor in suppressing growth. The central city added more
people and more businesses. Then a new constraint appeared. Goods and
workers could not move in and out of the dense center city quickly
enough. Again the solution was technological. A network of expressways,
mass transit systems, and helicopter ports on the tops of the tallest
buildings was constructed. The transportation limit was overcome, the
buildings grew taller, the population increased.
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Now most of the larger US cities have stopped growing. (Of
the ten largest, five—New York, Chicago, Philadelphia, Detroit,
and Baltimore—decreased in population from 1960 to 1970.
Washington, DC, showed no change. Los Angeles, Houston, Dallas, and
Indianapolis continued to grow, at least in part by annexing additional
land.)46 The wealthier people, who
have an economic choice, are moving to the ever-expanding ring of
suburbs around the cities. The central areas are characterized by noise,
pollution, crime, drug addiction, poverty, labor strikes, and breakdown
of social services. The quality of life in the city core has declined.
Growth has been stopped in part by problems with no technical
solutions.
A technical solution may be defined as "one that requires
a change only in the techniques of the natural sciences, demanding
little or nothing in the way of change in human values or ideas of
morality."47 Numerous problems today have
no technical solutions. Examples are the nuclear arms race, racial
tensions, and unemployment. Even if society's technological progress
fulfills all expectations, it may very well be a problem with no
technical solution, or the interaction of several such problems, that
finally brings an end to population and capital growth.
A choice of limits
Applying technology to the natural pressures that the environment exerts
against any growth process has been so successful in the past that a
whole culture has evolved around the principle of fighting against
limits rather than learning to live with them. This culture has been
reinforced by the apparent immensity of the earth and its resources and
by the relative smallness of man and his activities.
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But the relationship between the earth's limits and man's
activities is changing. The exponential growth curves are adding
millions of people and billions of tons of pollutants to the ecosystem
each year. Even the ocean, which once appeared virtually inexhaustible,
is losing species after species of its commercially useful animals.
Recent FAO statistics indicate that the total catch of the world's
fisheries decreased in 1969 for the first time since 1950, in spite of
more mechanized and intensive fishing practices. (Among commercial
species becoming increasingly scarce are Scandinavian herring, menhaden,
and Atlantic cod.)48
Yet man does not seem to learn by running into the earth's
obvious limits. The story of the whaling industry (shown in figure 43)
demonstrates, for one small system, the ultimate result of the attempt
to grow forever in a limited environment. Whalers have systematically
reached one limit after another and have attempted to overcome each one
by increases in power and technology. As a result, they have wiped out
one species after another. The outcome of this particular
grow–forever policy can only be the final extinction of both
whales and whalers. The alternative policy is the imposition of a man–determined limit on the number of
whales taken each year, set so that the whale population is maintained
at a steady-state level. The self–imposed limit on whaling would
be an unpleasant pressure that would prevent the growth of the industry.
But perhaps it would be preferable to the gradual disappearance of both
whales and whaling industry.
The basic choice that faces the whaling industry is the
same one that faces any society trying to overcome a natural limit with
a new technology. Is it better to try to live within
that limit by accepting a self-imposed restriction on growth?
Or
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is it preferable to go on growing until some other
natural limit arises, in the hope that at that time another
technological leap will allow growth to continue still longer?
For the last several hundred years human society has followed the second
course so consistently and successfully that the first choice has been
all but forgotten.
There may be much disagreement with the statement that
population and capital growth must stop soon. But
virtually no one will argue that material growth on this planet can go
on forever. At this point in man's history, the choice posed above is
still available in almost every sphere of human activity. Man can still
choose his limits and stop when he pleases by weakening some of the
strong pressures that cause capital and population growth, or by
instituting counterpressures, or both. Such counterpressures will
probably not be entirely pleasant. They will certainly involve profound
changes in the social and economic structures that have been deeply
impressed into human culture by centuries of growth. The alternative is
to wait until the price of technology becomes more than society can pay,
or until the side–effects of technology suppress growth
themselves, or until problems arise that have no technical solutions. At
any of those points the choice of limits will be gone. Growth will be
stopped by pressures that are not of human choosing, and that, as the
world model suggests, may
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be very much worse than those which society might choose for itself.
We have felt it necessary to dwell so long on an analysis
of technology here because we have found that technological optimism is
the most common and the most dangerous reaction to our findings from the
world model. Technology can relieve the symptoms of a problem without
affecting the underlying causes. Faith in technology as the ultimate
solution to all problems can thus divert our attention from the most
fundamental problem—the problem of growth in a finite
system—and prevent us from taking effective action to solve
it.
On the other hand, our intent is certainly not to brand
technology as evil or futile or unnecessary. We are technologists
ourselves, working in a technological institution. We strongly believe,
as we shall point out in the following chapter, that many of the
technological developments mentioned here—recycling, pollution
control devices, contraceptives—will be absolutely vital to the
future of human society if they are combined with
deliberate checks on growth. We would deplore an unreasoned
rejection of the benefits of technology as strongly as we argue here
against an unreasoned acceptance of them. Perhaps the best summary of
our position is the motto of the Sierra Club: "Not blind opposition to
progress, but opposition to blind progress."
We would hope that society will receive each new
technological advance by establishing the answers to three questions before the technology is widely adopted. The
questions are:
1. What will be the side-effects, both physical and social, if
this development is introduced on a large scale?
2. What social changes will be necessary before this
develop–
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ment can be implemented
properly, and how long will it take to achieve them?
3. If the development is fully successful and removes some
natural limit to growth, what limit will the growing system meet
next? Will society prefer its pressures to the ones this development
is designed to remove?
Let us go on now to investigate nontechnical approaches
for dealing with growth in a finite world.
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CHAPTER V THE STATE OF GLOBAL
EQUILIBRIUM
"Most persons think that a state in order to be happy ought to be large; but
even if they are right, they have no idea of what is a large and what a
small state....To the size of states there is a limit, as there is to
other things, plants, animals, implements; for none of these retain their
natural power when they are too large or too small, but they either wholly lose
their nature, or are spoiled. "
ARISTOTLE, 322 B.C.
We have seen that positive feedback loops operating without
any constraints generate exponential growth. In the world system two positive
feedback loops are dominant now, producing exponential growth of population and
of industrial capital.
In any finite system there must be constraints that can act to
stop exponential growth. These constraints are negative feedback loops. The
negative loops become stronger and stronger as growth approaches the ultimate
limit, or carrying capacity, of the system's environment. Finally the negative
loops balance or dominate the positive ones, and growth comes
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to an end. In the world system the negative feedback loops involve such
processes as pollution of the environment, depletion of nonrenewable resources,
and famine.
The delays inherent in the action of these negative loops tend to
allow population and capital to overshoot their ultimately sustainable levels.
The period of overshoot is wasteful of resources. It generally decreases the
carrying capacity of the environment as well, intensifying the eventual decline
in population and capital.
The growth–stopping pressures from negative feedback loops
are already being felt in many parts of human society. The major societal
responses to these pressures have been directed at the negative feedback loops
themselves. Technological solutions, such as those discussed in chapter IV, have
been devised to weaken the loops or to disguise the pressures they generate so
that growth can continue. Such means may have some short–term effect in
relieving pressures caused by growth, but in the long run they do nothing to
prevent the overshoot and subsequent collapse of the system.
Another response to the problems created by growth would be to
weaken the positive feedback loops that are generating
the growth. Such a solution has almost never been acknowledged as legitimate by
any modern society, and it has certainly never been effectively carried out.
What kinds of policies would such a solution involve? What sort of world would
result? There is almost no historical precedent for such an approach, and thus
there is no alternative but to discuss it in terms of models—either mental
models or formal, written models. How will the world model behave if we include
in it some policy to control growth deliberately? Will such a policy change
generate a "better" behavior mode?
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Whenever we use words such as "better" and begin choosing among
alternative model outputs, we, the experimenters, are inserting our own values
and preferences into the modeling process. The values built into each causal
relationship of the model are the real, operational values of the world to the
degree that we can determine them. The values that cause us to rank computer
outputs as "better" or "worse" are the personal values of the modeler or his
audience. We have already asserted our own value system by rejecting the
overshoot and collapse mode as undesirable. Now that we are seeking a "better"
result, we must define our goal for the system as clearly as possible. We are
searching for a model output that represents a world system that is:
1. sustainable without sudden and uncontrollable collapse; and
2. capable of satisfying the basic material requirements of all of its
people.
Now let us see what policies will bring about such behavior in the
world model.
DELIBERATE CONSTRAINTS ON GROWTH
You will recall that the positive feedback loop generating population growth
involves the birth rate and all the socio–economic factors that
influence the birth rate. It is counteracted by the negative loop of the
death rate.
The overwhelming growth in world population caused by the
positive birth-rate loop is a recent phenomenon, a result of mankind's very
successful reduction of worldwide mortality. The controlling negative
feedback loop has been weakened, allowing the positive loop to operate
virtually without constraint. There are only two ways to restore the
resulting im–
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balance. Either the birth rate must be brought down to equal the new, lower
death rate, or the death rate must rise again. All of the "natural"
constraints to population growth operate in the second way—they raise
the death rate. Any society wishing to avoid that result must take
deliberate action to control the positive feedback loop—to reduce the
birth rate.
In a dynamic model it is a simple matter to counteract runaway
positive feedback loops. For the moment let us suspend the requirement of
political feasibility and use the model to test the physical, if not the
social, implications of limiting population growth. We need only add to the
model one more causal loop, connecting the birth rate and the death rate. In
other words, we require that the number of babies born each year be equal to
the expected number of deaths in the population that year. Thus the positive
and negative feedback loops are exactly balanced. As the death rate
decreases, because of better food and medical care, the birth rate will
decrease
simultaneously. Such a requirement, which is as mathematically simple as it
is socially complicated, is for our purposes an experimental device, not
necessarily a political recommen–
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dation.* The result of inserting this policy into
the model in 1975 is shown in figure 44.
*This suggestion for stabilizing
population was originally proposed by Kenneth E.
Boulding in The Meaning of the 20th Century
(New York: : Harper and
Row., 1964).
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In figure 44 the positive feedback loop of population growth
is effectively balanced, and population remains constant. At first the birth
and death rates are low. But there is still one unchecked positive feedback
loop operating in the model— the one governing the growth of
industrial capital. The gain around that loop increases when population is
stabilized, resulting in a very rapid growth of income, food, and services
per capita. That growth is soon stopped, however, by depletion of
nonrenewable resources. The death rate then rises, but total population does
not decline because of our requirement that birth rate equal death rate
(clearly unrealistic here).
Apparently, if we want a stable system, it is not desirable to
let even one of the two critical positive feedback loops generate
uncontrolled growth. Stabilizing population alone is not sufficient to
prevent overshoot and collapse; a similar run with constant capital and
rising population shows that stabilizing capital alone is also not
sufficient. What happens if we bring both positive
feedback loops under control simultaneously? We can stabilize the capital
stock in the model by requiring that the investment rate equal the
depreciation rate, with an additional model link exactly analogous to the
population–stabilizing one.
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The result of stopping population growth in 1975 and
industrial capital growth in 1985 with no other changes is shown in figure
45. (Capital was allowed to grow until 1985 to raise slightly the average
material standard of living.) In this run
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the severe overshoot and collapse of figure 44 are prevented. Population and
capital reach constant values at a relatively high level of food, industrial
output, and services per person. Eventually, however, resource shortages
reduce industrial output and the temporarily stable state degenerates.
What model assumptions will give us a combination of a decent
living standard with somewhat greater stability than that attained in figure
45? We can improve the model behavior greatly by combining technological
changes with value changes that reduce the growth tendencies of the system.
Different combinations of such policies give us a series of computer outputs
that represent a system with reasonably high values of industrial output per
capita and with long-term stability. One example of such an output is shown
in figure 46.
The policies that produced the behavior shown in figure 46
are:
1. Population is stabilized by setting the birth rate equal to the
death rate in 1975. Industrial capital is allowed to increase naturally
until 1990, after which it, too, is stabilized, by setting the
investment rate equal to the depreciation rate.
2. To avoid a nonrenewable resource shortage such as that shown in
figure 45, resource consumption per unit of industrial output is reduced
to one-fourth of its 1970 value. (This and the following five policies
are introduced in 1975.)
3. To further reduce resource depletion and pollution, the
economic preferences of society are shifted more toward services such as
education and health facilities and less toward factory-produced
material goods. (This change is made through the relationship giving
"indicated" or "desired" services per capita as a function of rising
income.)
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4. Pollution generation per unit of industrial and agricultural
output is reduced to one-fourth of its 1970 value.
5. Since the above policies alone would result in a rather low
value of food per capita, some people would still be malnourished if the
traditional inequalities of distribution persist. To avoid this
situation, high value is placed on producing sufficient food for all people. Capital is therefore diverted to food
production even if such an investment would be considered "uneconomic."
(This change is carried out through the "indicated" food per capita
relationship.)
6.This emphasis on highly capitalized agriculture, while necessary
to produce enough food, would lead to rapid soil erosion and depletion
of soil fertility, destroying long-term stability in the agricultural
sector. Therefore the use of agricultural capital has been altered to
make soil enrichment and preservation a high priority. This policy
implies, for example, use of capital to compost urban organic wastes and
return them to the land (a practice that also reduces pollution).
7. The drains on industrial capital for higher services and food
production and for resource recycling and pollution control under the
above six conditions would lead to a low final level of industrial
capital stock. To counteract this effect, the average lifetime of
industrial capital is increased, implying better design for durability
and repair and less discarding because of obsolescence. This policy also
tends to reduce resource depletion and pollution.
In figure 46 the stable world population is only slightly
larger than the population today. There is more than twice as much food per
person as the average value in 1970, and world average lifetime is nearly 70
years. The average indus–
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trial output per capita is well above today's level, and services per capita
have tripled. Total average income per capita (industrial output, food, and
services combined) is about $1,800. This value is about half the present
average US income, equal to
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the present average European income, and three times the present average
world income. Resources are still being gradually depleted, as they must be
under any realistic assumption, but the rate of depletion is so slow that
there is time for technology and industry to adjust to changes in resource
availability.
The numerical constants that characterize this model run are
not the only ones that would produce a stable system. Other people or
societies might resolve the various trade–offs differently, putting
more or less emphasis on services or food or pollution or material income.
This example is included merely as an illustration of the levels of
population and capital that are physically
maintainable on the earth, under the most optimistic assumptions.
The model cannot tell us how to attain these levels. It can only indicate a
set of mutually consistent goals that are attainable.
Now let us go back at least in the general direction of the
real world and relax our most unrealistic assumptions—that we can
suddenly and absolutely stabilize population and capital. Suppose we retain
the last six of the seven policy changes that produced figure 46, but
replace the first policy, beginning in 1975, with the following:
1. The population has access to 100 percent effective birth
control.
2. The average desired family size is two children.
3. The economic system endeavors to maintain average industrial
output per capita at about the 1975 level. Excess industrial capability
is employed for producing consumption goods rather than increasing the
industrial capital investment rate above the depreciation rate.
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The model behavior that results from this change is shown in
figure 47. Now the delays in the system allow population to grow much larger
than it did in figure 46. As a consequence, material goods, food, and
services per capita remain lower than in previous runs (but still higher
than they are on a world average today).
We do not suppose that any single one of the policies
necessary to attain system stability in the model can or should be suddenly
introduced in the world by 1975. A society choosing stability as a goal
certainly must approach that goal gradually. It is important to realize,
however, that the longer exponential growth is allowed to continue, the
fewer possibilities remain for the final stable state. Figure 48 shows the
result of waiting until the year 2000 to institute the same policies that
were instituted in 1975 in figure 47.
In figure 48 both population and industrial output per capita
reach much higher values than in figure 47. As a result pollution builds to
a higher level and resources are severely depleted, in spite of the
resource–saving policies finally introduced. In fact, during the
25–year delay (from 1975 to 2000) in instituting the stabilizing
policies, resource consumption is about equal to the total 125–year
consumption from 1975 to 2100 of figure 47.
Many people will think that the changes we have introduced
into the model to avoid the growth–and–collapse behavior mode
are not only impossible, but unpleasant, dangerous, even disastrous in
themselves. Such policies as reducing the birth rate and diverting capital
from production of material goods, by whatever means they might be
implemented, seem unnatural and unimaginable, because they have not, in most
people's experience, been tried, or even seriously suggested. Indeed
there
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would be little point even in discussing such fundamental changes in the
functioning of modern society if we felt that the present pattern of
unrestricted growth were sustainable into the future. All the evidence
available to us, however, suggests that of the three
alternatives—unrestricted growth, a self–
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imposed limitation to growth, or a nature-imposed limitation to
growth—only the last two are actually possible.
Accepting the nature-imposed limits to growth requires no more
effort than letting things take their course and waiting to see what will
happen. The most probable result of that decision, as we have tried to show
here, will be an uncontrollable decrease in population and capital. The real
meaning of such a
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collapse is difficult to imagine because it might take so many different
forms. It might occur at different times in different parts of the world, or
it might be worldwide. It could be sudden or gradual. If the limit first
reached were that of food production, the nonindustrialized countries would
suffer the major population decrease. If the first limit were imposed by
exhaustion of nonrenewable resources, the industrialized countries would be
most affected. It might be that the collapse would leave the earth with its
carrying capacity for animal and plant life undiminished, or it might be
that the carrying capacity would be reduced or destroyed. Certainly whatever
fraction of the human population remained at the end of the process would
have very little left with which to build a new society in any form we can
now envision.
Achieving a self–imposed limitation to growth would
require much effort. It would involve learning to do many things in new
ways. It would tax the ingenuity, the flexibility, and the
self–discipline of the human race. Bringing a deliberate, controlled
end to growth is a tremendous challenge, not easily met. Would the final
result be worth the effort? What would humanity gain by such a transition,
and what would it lose? Let us consider in more detail what a world of
nongrowth might be like.
THE EQUILIBRIUM STATE
We are by no means the first people in man's written history to propose some
sort of nongrowing state for human society. A number of philosophers,
economists, and biologists have discussed such a state and called it by many
different names, with as many different meanings.*
We have, after much discussion, decided to call the state
of
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constant population and capital, shown in figures 46 and 47, by the term
"equilibrium." Equilibrium means a state of balance or equality between
opposing forces. In the dynamic terms of the world model, the opposing
forces are those causing population and capital stock to increase (high
desired family size, low birth control effectiveness, high rate of capital
investment) and those causing population and capital stock to decrease (lack
of food, pollution, high rate of depreciation or obsolescence). The word
"capital" should be understood to mean service, industrial, and agricultural
capital combined. Thus the most basic definition of the
state of global equilibrium is that population and capital are
essentially stable, with the forces tending to increase or decrease them
in a carefully controlled balance.
There is much room for variation within that definition. We
have only specified that the stocks of capital and population remain
constant, but they might theoretically be constant
*See, for instance:
Plato, Laws, 350
B.C.
Aristode, Politics, 322
B.C.
Thomas Robert Malthus, An Essay on the Principle
of Population, 1798.
John Stuart Mill, Principles of Political
Economy, 1857.
Harrison Brown, The Challenge of Mans
Future (New York: : Viking
Press., 1954).
Kenneth E. Boulding, "The Economics of
the Coming Spaceship Earth," in Environmental Quality in a Growing Economy, ed. H.
Jarrett (Baltimore, Md.: :
Johns Hopkins Press., 1966).
E. J. Mishan, The Costs of Economic
Growth (New York: : Frederick
A. Praeger., 1967).
Herman E. Daly, "Toward a
Stationary-State Economy," in The Patient
Earth, ed. J. Harte and Robert Socolow
(New York: : Holt, Rinehart, and
Winston., 1971).
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at a high level or a low level—or one might be high and the other low.
A tank of water can be maintained at a given level with a fast inflow and
outflow of water or with a slow trickle in and out. If the flow is fast, the
average drop of water will spend less time in the tank than if the flow is
slow. Similarly, a stable population of any size can be achieved with either
high, equal birth and death rates (short average lifetime) or low, equal
birth and death rates (long average lifetime). A stock of capital can be
maintained with high investment and depreciation rates or low investment and
depreciation rates. Any combination of these possibilities would fit into
our basic definition of global equilibrium.
What criteria can be used to choose among the many options
available in the equilibrium state? The dynamic interactions in the world
system indicate that the first decision that must be made concerns time. How long should the equilibrium state exist? If
society is only interested in a time span of 6 months or a year, the world
model indicates that almost any level of population and capital could be
maintained. If the time horizon is extended to 20 or 50 years, the options
are greatly reduced, since the rates and levels must be adjusted to ensure
that the capital investment rate will not be limited by resource
availability during that time span, or that the death rate will not be
uncontrollably influenced by pollution or food shortage. The longer a
society prefers to maintain the state of equilibrium, the lower the rates
and levels must be.
At the limit, of course, no population or capital level can be
maintained forever, but that limit is very far away in time if resources are
managed wisely and if there is a sufficiently long time horizon in planning.
Let us take as a reasonable time horizon the expected lifetime of a child
born into the
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world tomorrow—70 years if proper food and medical care are supplied.
Since most people spend a large part of their time and energy raising
children, they might choose as a minimum goal that the society left to those
children can be maintained for the full span of the children's lives.
If society's time horizon is as long as 70 years, the
permissible population and capital levels may not be too different from
those existing today, as indicated by the equilibrium run in figure 47
(which is, of course, only one of several possibilities). The rates would be
considerably different from those of today, however. Any society would
undoubtedly prefer that the death rate be low rather than high, since a
long, healthy life seems to be a universal human desire. To maintain
equilibrium with long life expectancy, the birth rate then must also be low.
It would be best, too, if the capital investment and depreciation rates were
low, because the lower they are, the less resource depletion and pollution
there will be. Keeping depletion and pollution to a minimum could either
increase the maximum size of the population and capital levels or increase
the length of time the equilibrium state could be maintained, depending on
which goal the society as a whole preferred.
By choosing a fairly long time horizon for its existence, and
a long average lifetime as a desirable goal, we have now arrived at a
minimum set of requirements for the state of global equilibrium. They
are:
1.The capital plant and the population are constant in
size. The birth rate equals the death rate and the capital
investment rate equals the depreciation rate.
2.All input and output rates—births, deaths,
investment, and depreciation—are kept to a
minimum.
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3.The levels of capital and population and the ratio of
the two are set in accordance with the values of the society.
They may be deliberately revised and slowly adjusted as the advance of
technology creates new options.
An equilibrium defined in this way does not mean stagnation.
Within the first two guidelines above, corporations could expand or fail,
local populations could increase or decrease, income could become more or
less evenly distributed. Technological advance would permit the services
provided by a constant stock of capital to increase slowly. Within the third
guideline, any country could change its average standard of living by
altering the balance between its population and its capital. Furthermore, a
society could adjust to changing internal or external factors by raising or
lowering the population or capital stocks, or both, slowly and in a
controlled fashion, with a predetermined goal in mind. The three points
above define a dynamic equilibrium, which need not
and probably would not "freeze" the world into the population–capital
configuration that happens to exist at the present time. The object in
accepting the above three statements is to create freedom for society, not
to impose a straitjacket.
What would life be like in such an equilibrium state? Would
innovation be stifled? Would society be locked into the patterns of
inequality and injustice we see in the world today? Discussion of these
questions must proceed on the basis of mental models, for there is no formal
model of social conditions in the equilibrium state. No one can predict what
sort of institutions mankind might develop under these new conditions. There
is, of course, no guarantee that the new society would be much better or
even much different from that which exists today. It seems possible,
however, that a society released
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from struggling with the many problems caused by growth may have more energy
and ingenuity available for solving other problems. In fact, we believe, as
we will illustrate below, that the evolution of a society that favors
innovation and technological development, a society based on equality and
justice, is far more likely to evolve in a state of global equilibrium than
it is in the state of growth we are experiencing today.
GROWTH IN THE EQUILIBRIUM STATE
In 1857 John Stuart Mill wrote:
It is scarcely necessary to remark that a stationary condition of capital
and population implies no stationary state of human improvement. There would
be as much scope as ever for all kinds of mental culture, and moral and
social progress; as much room for improving the Art of Living and much more
likelihood of its being improved.49
Population and capital are the only quantities that need be
constant in the equilibrium state. Any human activity that does not require
a large flow of irreplaceable resources or produce severe environmental
degradation might continue to grow indefinitely. In particular, those
pursuits that many people would list as the most desirable and satisfying
activities of man—education, art, music, religion, basic scientific
research, athletics, and social interactions—could flourish.
All of the activities listed above depend very strongly on two
factors. First, they depend upon the availability of some surplus production
after the basic human needs of food and shelter have been met. Second, they
require leisure time. In any equilibrium state the relative levels of
capital and population could be adjusted to assure that human material needs
are fulfilled at any desired level. Since the amount of material production
would be essentially fixed, every improvement in
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production methods could result in increased leisure for the
population—leisure that could be devoted to any activity that is
relatively nonconsuming and nonpolluting, such as those listed above. Thus,
this unhappy situation described by Bertrand Russell could be avoided:
Suppose that, at a given moment, a certain number of people are engaged in
the manufacture of pins. They make as many pins as the world needs, working
(say) eight hours a day. Someone makes an invention by which the same number
of men can make twice as many pins as before. But the world does not need
twice as many pins. Pins are already so cheap that hardly any more will be
bought at a lower price. In a sensible world, everybody concerned in the
manufacture of pins would take to working four hours instead of eight, and
everything else would go on as before. But in the actual world this would be
thought demoralizing. The men still work eight hours, there are too many
pins, some employers go bankrupt, and half the men previously concerned in
making pins are thrown out of work. There is, in the end, just as much
leisure as on the other plan, but half the men are totally idle while half
are still overworked. In this way it is insured that the unavoidable leisure
shall cause misery all around instead of being a universal source of
happiness. Can anything more insane be imagined?50
But would the technological improvements that permit the
production of pins or anything else more efficiently be forth–coming
in a world where all basic material needs are fulfilled and additional
production is not allowed? Does man have to be pushed by hardship and the
incentive of material growth to devise better ways to do things?
Historical evidence would indicate that very few key
inventions have been made by men who had to spend all their energy
overcoming the immediate pressures of survival. Atomic energy was discovered
in the laboratories of basic science by individuals unaware of any threat of
fossil fuel depletion. The
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first genetic experiments, which led a hundred years later to high-yield
agricultural crops, took place in the peace of a European monastery.
Pressing human need may have forced the application of these basic
discoveries to practical problems, but only freedom from need produced the
knowledge necessary for the practical applications.
Technological advance would be both necessary and welcome in
the equilibrium state. A few obvious examples of the kinds of practical
discoveries that would enhance the workings of a steady state society
include:
•new methods of waste collection, to decrease pollution and make
discarded material available for recycling;
•more efficient techniques of recycling, to reduce rates of resource
depletion;
•better product design to increase product lifetime and promote easy
repair, so that the capital depreciation rate would be minimized;
•harnessing of incident solar energy, the most pollution–free
power source;
•methods of natural pest control, based on more complete understanding
of ecological interrelationships;
•medical advances that would decrease the death rate;
•contraceptive advances that would facilitate the equalization of the
birth rate with the decreasing death rate.
As for the incentive that would encourage men to produce such
technological advances, what better incentive could there be than the
knowledge that a new idea would be translated into a visible improvement in
the quality of life? Historically mankind's long record of new inventions
has resulted in crowding, deterioration of the environment, and greater
social
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inequality because greater productivity has been absorbed by population and
capital growth. There is no reason why higher productivity could not be
translated into a higher standard of living or more leisure or more pleasant
surroundings for everyone, if these goals replace growth as the primary
value of society.
EQUALITY IN THE EQUILIBRIUM STATE
One of the most commonly accepted myths in our present society is the
promise that a continuation of our present patterns of growth will lead to
human equality. We have demonstrated in various parts of this book that
present patterns of population and capital growth are actually increasing
the gap between the rich and the poor on a worldwide basis, and that the
ultimate result of a continued attempt to grow according to the present
pattern will be a disastrous collapse.
The greatest possible impediment to more equal distribution of
the world's resources is population growth. It seems to be a universal
observation, regrettable but understandable, that, as the number of people
over whom a fixed resource must be distributed increases, the equality of
distribution decreases. Equal sharing becomes social suicide if the average
amount available per person is not enough to maintain life. FAO studies of
food distribution have actually documented this general observation.
Analysis of distribution curves shows that when the food supplies of a group
diminish, inequalities in intake are accentuated, while the number of
undernourished families increases more than in proportion to the deviation
from the mean. Moreover, the food intake deficit grows with the size of
households so that large families, and their children in particular, are
statistically the most likely to be underfed.51
In a long–term equilibrium state, the relative levels of
popula–
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tion and capital, and their relationships to fixed constraints such as land,
fresh water, and mineral resources, would have to be set so that there would
be enough food and material production to maintain everyone at (at least) a
subsistence level. One barrier to equal distribution would thus be removed.
Furthermore, the other effective barrier to equality—the promise of
growth—could no longer be maintained, as Dr. Herman E. Daly has
pointed out:
For several reasons the important issue of the stationary state will be
distribution, not production. The problem of relative shares can no longer
be avoided by appeals to growth. The argument that everyone should be happy
as long as his absolute share of wealth increases, regardless of his
relative share, will no longer be available. . . . The stationary state
would make fewer demands on our environmental resources, but much greater
demands on our moral resources.52
There is, of course, no assurance that humanity's moral
resources would be sufficient to solve the problem of income distribution,
even in an equilibrium state. However, there is even less assurance that
such social problems will be solved in the present state of growth, which is
straining both the moral and the physical resources of the world's
people.
The picture of the equilibrium state we have drawn here is
idealized, to be sure. It may be impossible to achieve in the form described
here, and it may not be the form most people on earth would choose. The only
purpose in describing it at all is to emphasize that global equilibrium need
not mean an end to progress or human development. The possibilities within
an equilibrium state are almost endless.
An equilibrium state would not be free of pressures," since no
society can be free of pressures. Equilibrium would require trading certain
human freedoms, such as producing unlimited
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numbers of children or consuming uncontrolled amounts of resources, for
other freedoms, such as relief from pollution and crowding and the threat of
collapse of the world system. It is possible that new freedoms might also
arise—universal and unlimited education, leisure for creativity and
inventiveness, and, most important of all, the freedom from hunger and
poverty enjoyed by such a small fraction of the world's people today.
THE TRANSITION FROM GROWTH TO GLOBAL EQUILIBRIUM
We can say very little at this point about the practical,
day–by–day steps that might be taken to reach a desirable,
sustainable state of global equilibrium. Neither the world model nor our own
thoughts have been developed in sufficient detail to understand all the
implications of the transition from growth to equilibrium. Before any part
of the world's society embarks deliberately on such a transition, there must
be much more discussion, more extensive analysis, and many new ideas
contributed by many different people. If we have stimulated each reader of
this book to begin pondering how such a transition might be carried out, we
have accomplished our immediate goal.
Certainly much more information is needed to manage the
transition to global equilibrium. In the process of sifting the world's data
and incorporating it into an organized model, we have become aware of the
great need for more facts—for numbers that are
scientifically measurable but which have not yet been measured. The most
glaring deficiencies in present knowledge occur in the pollution sector of
the model. How long does it take for any given pollutant to travel from its
point of release to its point of entrance into the human body? Does the time
required for the processing of any pollutant into
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harmless form depend on the level of pollutant? Do several different
pollutants acting together have a synergistic effect on human health? What
are the long–term effects of low–level dosages on humans and
other organisms? There is also a need for more information about rates of
soil erosion and land wastage under intensified modern agricultural
practices.
From our own vantage point as systems analysts, of course, we
would recommend that the search for facts not be random but be governed by a
greatly increased emphasis on establishing system
structure. The behavior of all complicated social systems is
primarily determined by the web of physical, biological, psychological, and
economic relationships that binds together any human population, its natural
environment, and its economic activities. Until the underlying structures of
our socioeconomic systems are thoroughly analyzed, they cannot be managed
effectively, just as an automobile cannot be maintained in good running
condition without a knowledge of how its many parts influence each other.
Studies of system structure may reveal that the introduction into a system
of some simple stabilizing feedback mechanism will solve many difficulties.
There have been interesting suggestions along that line already —for
example, that the total costs of pollution and resource depletion be
included in the price of a product, or that every user of river water be
required to place his intake pipe downstream from his
effluent pipe.
The final, most elusive, and most important information we
need deals with human values. As soon as a society recognizes that it cannot
maximize everything for everyone, it must begin to make choices. Should
there be more people or more wealth, more wilderness or more automobiles,
more food for the poor or more services for the rich? Establishing the
societal an–
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swers to questions like these and translating those answers into policy is
the essence of the political process. Yet few people in any society even
realize that such choices are being made every day, much less ask themselves
what their own choices would be. The equilibrium society will have to weigh
the trade-offs engendered by a finite earth not only with consideration of
present human values but also with consideration of future generations. To
do that, society will need better means than exist today for clarifying the
realistic alternatives available, for establishing societal goals, and for
achieving the alternatives that are most consistent with those goals. But
most important of all, long-term goals must be specified and short-term
goals made consistent with them.
Although we underline the need for more study and discussion
of these difficult questions, we end on a note of urgency. We hope that
intensive study and debate will proceed simultaneously with an ongoing
program of action. The details are not yet specified, but the general
direction for action is obvious. Enough is known already to analyze many
proposed policies in terms of their tendencies to promote or to regulate
growth. Numerous nations have adapted or are considering programs to
stabilize their populations. Some localized areas are also trying to reduce
their rates of economic growth.53 These
efforts are weak at the moment, but they could be strengthened very quickly
if the goal of equilibrium were recognized as desirable and important by any
sizable part of human society.
We have repeatedly emphasized the importance of the natural
delays in the population-capital system of the world. These delays mean, for
example, that if Mexico's birth rate gradually declined from its present
value to an exact replacement value by the year 2000, the country's
population would
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THE STATE OF GLOBAL EQUILIBRIUM
continue to grow until the year 2060. During that time the population would
grow from 50 million to 130 million.54 If the
United States population had two children per family starting now and if
there were no net immigration, the population would still continue to grow
until the year 2037, and it would increase from 200 million to 266
million.55 If world population as a whole reached a
replacement–size family by the year 2000 (at which time the population
would be 5.8 billion), the delays caused by the age structure would result
in a final leveling–off of population at 8.2 billion56 (assuming that the death rate would not rise
before then—an unlikely assumption, according to our model
results).
Taking no action to solve these problems is equivalent to
taking strong action. Every day of continued exponential growth brings the
world system closer to the ultimate limits to that growth. A decision to do
nothing is a decision to increase the risk of collapse. We cannot say with
certainty how much longer mankind can postpone initiating deliberate control
of his growth before he will have lost the chance for control. We suspect on
the basis of present knowledge of the physical constraints of the planet
that the growth phase cannot continue for another one hundred years. Again,
because of the delays in the system, if the global society waits until those
constraints are unmistakably apparent, it will have waited too long.
If there is cause for deep concern, there is also cause for
hope. Deliberately limiting growth would be difficult, but not impossible.
The way to proceed is clear, and the necessary steps, although they are new
ones for human society, are well within human capabilities. Man possesses,
for a small moment in his history, the most powerful combination of
knowledge, tools,
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and resources the world has ever known. He has all that is physically
necessary to create a totally new form of human society—one that would
be built to last for generations. The two missing ingredients are a
realistic, long-term goal that can guide mankind to the equilibrium society
and the human will to achieve that goal. Without such a goal and a
commitment to it, short-term concerns will generate the exponential growth
that drives the world system toward the limits of the earth and ultimate
collapse. With that goal and that commitment, mankind would be ready now to
begin a controlled, orderly transition from growth to global
equilibrium.
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COMMENTARY
In inviting the MIT team to undertake this investigation, we had two immediate
objectives in mind. One was to gain insights into the limits of our world system
and the constraints it puts on human numbers and activity. Nowadays, more than
ever before, man tends toward continual, often accelerated, growth—of
population, land occupancy, production, consumption, waste, etc.—blindly
assuming that his environment will permit such expansion, that other groups will
yield, or that science and technology will remove the obstacles. We wanted to
explore the degree to which this attitude toward growth is compatible with the
dimensions of our finite planet and with the fundamental needs of our emerging
world society— from the reduction of social and political tensions to
improvement in the quality of life for all.
A second objective was to help identify and study the dominant
elements, and their interactions, that influence the long–term behavior of
world systems. Such knowledge, we believe, cannot be gathered by concentrating
on national systems and short–run analyses, as is the current practice.
The project was not intended as a piece of futurology. It was intended to be,
and is, an analysis of current trends, of their influence on each
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COMMENTARY
other, and of their possible outcomes. Our goal was to
provide warnings of potential world crisis if these trends are allowed to
continue, and thus offer an opportunity to make changes in our political,
economic, and social systems to ensure that these crises do not take place.
The report has served these purposes well. It represents a bold
step toward a comprehensive and integrated analysis of the world situation, an
approach that will now require years to refine, deepen, and extend.
Nevertheless, this report is only a first step. The limits to growth it examines
are only the known uppermost physical limits imposed by the finiteness of the
world system. In reality, these limits are further reduced by political, social,
and institutional constraints, by inequitable distribution of population and
resources, and by our inability to manage very large intricate systems.
But the report serves further purposes. It advances tentative
suggestions for the future state of the world and opens new perspectives for
continual intellectual and practical endeavor to shape that future.
We have presented the findings of this report at two international
meetings. Both were held in the summer of 1971, one in Moscow and the other in
Rio de Janeiro. Although there were many questions and criticisms raised, there
was no substantial disagreement with the perspectives described in this report.
A preliminary draft of the report was also submitted to some forty individuals,
most of them members of The Club of Rome, for their comments. It may be of
interest to mention some of the main points of criticism:
1. Since models can accommodate only a limited number of variables,
the interactions studied are only partial. It was
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COMMENTARY
pointed out that in a global model such as the one used
in this study the degree of aggregation is necessarily high as well.
Nevertheless, it was generally recognized that, with a simple world model,
it is possible to examine the effect of a change in basic assumptions or to
simulate the effect of a change in policy to see how such changes influence
the behavior of the system over time. Similar experimentation in the real
world would be lengthy, costly, and in many cases impossible.
2. It was suggested that insufficient weight had been given to the
possibilities of scientific and technological advances in solving certain
problems, such as the development of foolproof contraceptive methods, the
production of protein from fossil fuels, the generation or harnessing of
virtually limitless energy (including pollution–free solar energy),
and its subsequent use for synthesizing food from air and water and for
extracting minerals from rocks. It was agreed, however, that such
developments would probably come too late to avert demographic or
environmental disaster. In any case they probably would only delay rather
than avoid crisis, for the problematique consists of issues that require
more than technical solutions.
3. Others felt that the possibility of discovering stocks of raw
materials in areas as yet insufficiently explored was much greater than the
model assumed. But, again, such discoveries would only postpone shortage
rather than eliminate it. It must, however, be recognized that extension of
resource availability by several decades might give man time to find
remedies.
4. Some considered the model too "technocratic," observing that it did
not include critical social factors, such as the effects of adoption of
different value systems. The chairman of the
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Moscow meeting summed up this point when he said, "Man
is no mere biocybernetic device." This criticism is readily admitted. The
present model considers man only in his material system because valid social
elements simply could not be devised and introduced in this first effort.
Yet, despite the model's material orientation, the conclusions of the study
point to the need for fundamental change in the values of society.
Overall, a majority of those who read this report concurred with
its position. Furthermore, it is clear that, if the arguments submitted in the
report (even after making allowance for justifiable criticism) are considered
valid in principle, their significance can hardly be overestimated.
Many reviewers shared our belief that the essential significance of
the project lies in its global concept, for it is through knowledge of wholes
that we gain understanding of components, and not vice versa. The report
presents in straightforward form the alternatives confronting not one nation or
people but all nations and all peoples, thereby compelling a reader to raise his
sights to the dimensions of the world problematique. A drawback of this approach
is of course that —given the heterogeneity of world society, national
political structures, and levels of development—the conclusions of the
study, although valid for our planet as a whole, do not apply in detail to any
particular country or region.
It is true that in practice events take place in the world
sporadically at points of stress—not generally or simultaneously
throughout the planet. So, even if the consequences anticipated by the model
were, through human inertia and political difficulties, allowed to occur, they
would no doubt appear first in a series of local crises and disasters.
But it is probably no less true that these crises would have
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COMMENTARY
repercussions worldwide and that many nations and people, by
taking hasty remedial action or retreating into isolationism and attempting
self–sufficiency, would but aggravate the conditions operating in the
system as a whole. The interdependence of the various components of the world
system would make such measures futile in the end. War, pestilence, a raw
materials starvation of industrial economies, or a generalized economic decay
would lead to contagious social disintegration.
Finally, the report was considered particularly valuable in
pointing out the exponential nature of human growth within a closed system, a
concept rarely mentioned or appreciated in practical politics in spite of its
immense implications for the future of our finite planet. The MIT project gives
a reasoned and systematic explanation of trends of which people are but dimly
aware.
The pessimistic conclusions of the report have been and no doubt
will continue to be a matter for debate. Many will believe that, in population
growth, for instance, nature will take remedial action, and birth rates will
decline before catastrophe threatens. Others may simply feel that the trends
identified in the study are beyond human control; these people will wait for
"something to turn up." Still others will hope that minor corrections in present
policies will lead to a gradual and satisfactory readjustment and possibly to
equilibrium. And a great many others are apt to put their trust in technology,
with its supposed cornucopia of cure–all solutions.
We welcome and encourage this debate. It is important, in our
opinion, to ascertain the true scale of the crisis confronting mankind and the
levels of severity it is likely to reach during the next decades.
From the response to the draft report we distributed, we
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COMMENTARY
believe this book will cause a growing number of people
throughout the world to ask themselves in earnest whether the momentum of
present growth may not overshoot the carrying capacity of this planet—and
to consider the chilling alternatives such an overshoot implies for ourselves,
our children, and our grandchildren.
How do we, the sponsors of this project, evaluate the report ? We
cannot speak definitively for all our colleagues in The Club of Rome, for there
are differences of interest, emphasis, and judgment among them. But, despite the
preliminary nature of the report, the limits of some of its data, and the
inherent complexity of the world system it attempts to describe, we are
convinced of the importance of its main conclusions. We believe that it contains
a message of much deeper significance than a mere comparison of dimensions, a
message relevant to all aspects of the present human predicament.
Although we can here express only our preliminary views,
recognizing that they still require a great deal of reflection and ordering, we
are in agreement on the following points:
1. We are convinced that realization of the quantitative restraints of the world
environment and of the tragic consequences of an overshoot is essential to the
initiation of new forms of thinking that will lead to a fundamental revision of
human behavior and, by implication, of the entire fabric of present–day
society.
It is only now that, having begun to understand something of the interactions
between demographic growth and economic growth, and having reached unprecedented
levels in both, man is forced to take account of the limited dimensions of
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COMMENTARY
his planet and the ceilings to his presence and activity on
it. For the first time, it has become vital to inquire into the cost of
unrestricted material growth and to consider alternatives to its
continuation.
2. We are further convinced that demographic pressure in the world has already
attained such a high level, and is moreover so unequally distributed, that this
alone must compel mankind to seek a state of equilibrium on our planet.
Underpopulated areas still exist; but, considering the world as a
whole, the critical point in population growth is approaching, if it has not
already been reached. There is of course no unique optimum, long–term
population level; rather, there are a series of balances between population
levels, social and material standards, personal freedom, and other elements
making up the quality of life. Given the finite and diminishing stock of
nonrenewable resources and the finite space of our globe, the principle must be
generally accepted that growing numbers of people will eventually imply a lower
standard of living—and a more complex problematique. On the other hand, no
fundamental human value would be endangered by a leveling off of demographic
growth.
3. We recognize that world equilibrium can become a reality only if the lot of
the so–called developing countries is substantially improved, both in
absolute terms and relative to the economically developed nations, and we affirm
that this improvement can be achieved only through a global strategy.
Short of a world effort, today's already explosive gaps and
inequalities will continue to grow larger. The outcome can only be disaster,
whether due to the selfishness of individual countries that continue to act
purely in their own interests,
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or to a power struggle between the developing and developed
nations. The world system is simply not ample enough nor generous enough to
accommodate much longer such egocentric and conflictive behavior by its
inhabitants. The closer we come to the material limits to the planet, the more
difficult this problem will be to tackle.
4. We affirm that the global issue of development is, however, so closely
interlinked with other global issues that an overall strategy must be evolved to
attack all major problems, including in particular those of man's relationship
with his environment.
With world population doubling time a little more than 30 years,
and decreasing, society will be hard put to meet the needs and expectations of
so many more people in so short a period. We are likely to try to satisfy these
demands by overexploiting our natural environment and further impairing the
life–supporting capacity of the earth. Hence, on both sides of the
man–environment equation, the situation will tend to worsen dangerously.
We cannot expect technological solutions alone to get us out of this vicious
circle. The strategy for dealing with the two key issues of development and
environment must be conceived as a joint one.
5. We recognize that the complex world problematique is to a great extent
composed of elements that cannot be expressed in measurable terms. Nevertheless,
we believe that the predominantly quantitative approach used in this report is
an indispensable tool for understanding the operation of the problematique. And
we hope that such knowledge can lead to a mastery of its elements.
Although all major world issues are fundamentally linked,
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no method has yet been discovered to tackle the whole
effectively. The approach we have adopted can be extremely useful in
reformulating our thinking about the entire human predicament. It permits us to
define the balances that must exist within human society, and between human
society and its habitat, and to perceive the consequences that may ensue when
such balances are disrupted.
6. We are unanimously convinced that rapid, radical redressment of the present
unbalanced and dangerously deteriorating world situation is the primary task
facing humanity.
Our present situation is so complex and is so much a reflection of
man's multiple activities, however, that no combination of purely technical,
economic, or legal measures and devices can bring substantial improvement.
Entirely new approaches are required to redirect society toward goals of
equilibrium rather than growth. Such a reorganization will involve a supreme
effort of understanding, imagination, and political and moral resolve. We
believe that the effort is feasible and we hope that this publication will help
to mobilize forces to make it possible.
7. This supreme effort is a challenge for our generation. It cannot be passed on
to the next. The effort must be resolutely undertaken without delay, and
significant redirection must be achieved during this decade.
Although the effort may initially focus on the implications of growth,
particularly of population growth, the totality of the world problematique will
soon have to be addressed. We believe in fact that the need will quickly become
evident for social innovation to match technical change, for radical reform of
institutions and political processes at all levels, including
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the highest, that of world polity. We are confident that our
generation will accept this challenge if we understand the tragic consequences
that inaction may bring.
8. We have no doubt that if mankind is to embark on a new course, concerted
international measures and joint long–term planning will be necessary on a
scale and scope without precedent.
Such an effort calls for joint endeavor by all peoples, whatever
their culture, economic system, or level of development. But the major
responsibility must rest with the more developed nations, not because they have
more vision or humanity, but because, having propagated the growth syndrome,
they are still at the fountainhead of the progress that sustains it. As greater
insights into the condition and workings of the world system are developed,
these nations will come to realize that, in a world that fundamentally needs
stability, their high plateaus of development can be justified or tolerated only
if they serve not as springboards to reach even higher, but as staging areas
from which to organize more equitable distribution of wealth and income
worldwide.
9. We unequivocally support the contention that a brake imposed on world
demographic and economic growth spirals must not lead to a freezing of the status quo of economic development of the world's
nations.
If such a proposal were advanced by the rich nations, it would be
taken as a final act of neocolonialism. The achievement of a harmonious state of
global economic, social, and ecological equilibrium must be a joint venture
based on joint conviction, with benefits for all. The greatest leadership will
be demanded from the economically developed countries, for
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the first step toward such a goal would be for them to
encourage a deceleration in the growth of their own material output while, at
the same time, assisting the developing nations in their efforts to advance
their economies more rapidly.
10. We affirm finally that any deliberate attempt to reach a rational and
enduring state of equilibrium by planned measures, rather than by chance or
catastrophe, must ultimately be founded on a basic change of values and goals at
individual, national, and world levels.
This change is perhaps already in the air, however faintly. But our
tradition, education, current activities, and interests will make the
transformation embattled and slow. Only real comprehension of the human
condition at this turning point in history can provide sufficient motivation for
people to accept the individual sacrifices and the changes in political and
economic power structures required to reach an equilibrium state.
The question remains of course whether the world situation is in
fact as serious as this book, and our comments, would indicate. We firmly
believe that the warnings this book contains are amply justified, and that the
aims and actions of our present civilization can only aggravate the problems of
tomorrow. But we would be only too happy if our tentative assessments should
prove too gloomy.
In any event, our posture is one of very grave concern, but not of
despair. The report describes an alternative to unchecked and disastrous growth
and puts forward some thoughts on the policy changes that could produce a stable
equilibrium for mankind. The report indicates that it may be within our reach to
provide reasonably large populations with a good material life plus
opportunities for limitless individual and
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COMMENTARY
social development. We are in substantial agreement with
that view, although we are realistic enough not to be carried away by purely
scientific or ethical speculations.
The concept of a society in a steady state of economic and
ecological equilibrium may appear easy to grasp, although the reality is so
distant from our experience as to require a Copernican revolution of the mind.
Translating the idea into deed, though, is a task filled with overwhelming
difficulties and complexities. We can talk seriously about where to start only
when the message of The Limits to Growth, and its sense of
extreme urgency, are accepted by a large body of scientific, political, and
popular opinion in many countries. The transition in any case is likely to be
painful, and it will make extreme demands on human ingenuity and determination.
As we have mentioned, only the conviction that there is no other avenue to
survival can liberate the moral, intellectual, and creative forces required to
initiate this unprecedented human undertaking.
But we wish to underscore the challenge rather than the difficulty
of mapping out the road to a stable state society. We believe that an
unexpectedly large number of men and women of all ages and conditions will
readily respond to the challenge and will be eager to discuss not if but how we can create this new
future.
The Club of Rome plans to support such activity in many ways. The
substantive research begun at MIT on world dynamics will be continued both at
MIT and through studies conducted in Europe, Canada, Latin America, the Soviet
Union, and Japan. And, since intellectual enlightenment is without effect if it
is not also political, The Club of Rome also will encourage the creation of a
world forum where statesmen,
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policy–makers, and scientists can discuss the dangers
and hopes for the future global system without the constraints of formal
intergovernmental negotiation.
The last thought we wish to offer is that man must explore
himself—his goals and values—as much as the world he seeks to
change. The dedication to both tasks must be unending. The crux of the matter is
not only whether the human species will survive, but even more whether it can
survive without falling into a state of worthless existence.
The Executive Committee of The Club of Rome
ALEXANDER KING
SABURO OKITA
AURELIO PECCEI
EDUARD PESTEL
HUGO THIEMANN
CARROLL WILSON
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APPENDIX: Related Studies
Papers related to the MIT System Dynamics Group–Club of
Rome Project on the Predicament of Mankind are listed below. Most of these
papers are available in one volume,Toward Global Equilibrium : Collected Papers,
Dennis L. Meadows, editor. Published by
Wright–Allen Press, Inc.., 238
Main Street, Cambridge, Massachusetts 02142: .
ANDERSON, ALISON AND ANDERSON, JAY M.
"System Simulation to Test Environmental Policy III: The Flow of
Mercury through the Environment." Mimeographed.
Cambridge, Mass.: : Massachusetts
Institute of Technology., 1971.
ANDERSON, JAY M.
"System Simulation to Test Environmental Policy II: The
Eutrophication of Lakes." Mimeographed. Cambridge,
Mass.: : Massachusetts Institute of
Technology., 1971.
BEHRENS, WILLIAM W. III.
"The Dynamics of Natural Resource Utilization." Paper
presented at the 1971 Summer Computer Simulation Conference, July 1971,
Boston, Massachusetts, sponsored by the Board of Simulation Conferences,
Denver, Colorado.
BEHRENS, WILLIAM W. III AND MEADOWS, DENNIS L.
"The Determinants of Long–Term Resource Availability."
Paper presented at the annual meeting of the American Association for the
Advancement of Science, January 1971, Philadelphia, Pennsylvania.
Page 199
APPENDIX
CHOUCRI, NAZLI; LAIRD, MICHAEL; AND MEADOWS, DENNIS L.
"Resource Scarcity and Foreign Policy: A Simulation Model of
International Conflict." Paper presented at the annual meeting
of the American Association for the Advancement of Science, January 1971,
Philadelphia, Pennsylvania.
FORRESTER, JAY W.
"Counterintuitive Nature of Social Systems."Technology Review
vol. 73 (1971):
pp. 53.
FORRESTER, JAY W.
World Dynamics. Cambridge, Mass.: :
Wright–Allen Pres.s, 1971.
HARBORDT, STEFFEN C.
"Linking Socio–Political Factors to the World Model."
Mimeographed. Cambridge, Mass.: :
Massachusetts Institute of Technology., 1971.
MEADOWS, DONELLA H.
"The Dynamics of Population Growth in the Traditional Agricultural
Village." Mimeographed. Cambridge, Mass.: :
Massachusetts Institute of Technology., 1971.
MEADOWS, DONELLA H.
"Testimony Before the Education Committee of the Massachusetts Great
and General Court on Behalf of the House Bill 3787." Republished
as "Reckoning with Recklessness,"Ecology Today, January
1972, pp. p. 11.
MEADOWS, DENNIS L.
The Dynamics of Commodity Production Cycles.
Cambridge, Mass.: : Wright–Allen
Press., 1970.
MEADOWS, DENNIS L.
"MIT–Club of Rome Project on the Predicament of
Mankind." Mimeographed. Cambridge, Mass.: :
Massachusetts Institute of Technology., 1971.
MEADOWS, DENNIS L.
"Some Requirements of a Successful Environmental
Program."Hearings of the Subcommittee on Air and Water Pollution of
the Senate Committee on Public Works, Part I, May 3, 1971.
Washington, DC: : Government Printing
Office., 1971.
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APPENDIX
MILLING, PETER.
"A Simple Analysis of Labor Displacement and Absorption in a Two
Sector Economy." Mimeographed. Cambridge,
Mass.: : Massachusetts Institute of
Technology., 1971.
NAILL, ROGER F. "The Discovery Life Cycle of a
Finite Resource: A Case Study of US Natural Gas." Mimeographed.
Cambridge, Mass.: : Massachusetts
Institute of Technology., 1971.
RANDERS, JøRGEN.
"The Dynamics of Solid Waste Generation." Mimeographed.
Cambridge, Mass: .: Massachusetts
Institute of Technology., 1971.
RANDERS, JøRGEN AND MEADOWS, DONELLA H. "The Carrying Capacity of our Global Environment: A Look at the
Ethical Alternatives." In Western Man and
Environmental Ethics, ed. Ian Barbour.
Reading, Mass.: :
Addison–Wesley., 1972.
RANDERS, JøRGEN AND MEADOWS, DENNIS L.
"System Simulation to Test Environmental Policy I: A Sample Study
of DDT Movement in the Environment." Mimeographed.
Cambridge, Mass.: : Massachusetts
Institute of Technology., 1971.
SHANTZIS, STEPHEN B. AND BEHRENS, WILLIAM W. III.
"Population Control Mechanisms in a Primitive Agricultural
Society." Mimeographed. Cambridge, Mass.: :
Massachusetts Institute of Technology., 1971.
Page 201
NOTES
1
A. M. Carr–Saunders, World Population:
Past Growth and Present Trends (Oxford: :
Clarendon Press., 1936), pp. p. 42.
2
US Agency for International Development,
Population Program Assistance (Washington,
DC: : Government Printing Office.,
1970), pp. p.
172.
3World Population Data Sheet 1968 (Washington,
DC: : Population Reference Bureau.,
1968).4
Lester R. Brown, Seeds of Change
(New York: : Praeger
Publishers., 1970), pp. p. 135.
5
President's Science Advisory Panel on the World Food
Supply, The World Food Problem
(Washington, DC: : Government Printing
Office., 1967)pp. 2:5.
6
President's Science Advisory Panel on the World Food
Supply, The World Food Problem, pp. 2:423.
7
President's Science Advisory Panel on the World Food
Supply, The World Food Problem, pp. 2:460–69.
8
UN Food and Agriculture Organization,
Provisional Indicative World Plan for Agricultural
Development (Rome: : UN Food
and Agriculture Organization., 1970) pp. 1:41.
9 Data from an Economic Research Service
survey, reported by Rodney J. Arkley in
"Urbanization of Agricultural Land in California,"
mimeographed (Berkeley, Calif.: :
University of California., 1970).
Page 202
NOTES
10
Paul R. Ehrlich and Anne H. Ehrlich,
Population, Resources, Environment (San
Francisco, Calif.: : W. H. Freeman and
Company., 1970), pp. p. 72.
11Mans Impact on the Global Environment, Report of the
Study of Critical Environmental Problems
(Cambridge, Mass.: : MIT
Press., 1970), pp. p. 118.
12First Annual Report of the Council on Environmental
Quality (Washington, DC: :
Government Printing Office., 1970), pp. p.
158.
13
US Bureau of Mines, Mineral Facts and
Problems, 1970 (Washington, DC: :
Government Printing Office., 1970), pp. p.
247.
13
US Bureau of Mines, Mineral Facts and
Problems, 1970 (Washington, DC: :
Government Printing Office., 1970), pp. p.
247.
14 Mercury data from US
Bureau of Mines, Minerals Yearbook
(Washington, DC: : Government Printing
Office., 1967) pp. 1(2):724 and US Bureau of
Mines, Commodity Data Summary
(Washington, DC: : Government Printing
Office., January 1971),
pp. p. 90. Lead data from
Metal Statistics (Somerset,
NJ: : American Metal Market Company.,
1970), pp. p.
215.
15
G. Evelyn Hutchinson, "The
Biosphere," Scientific American,
September 1970, pp. p.
53.
16
Chauncey Starr, "Energy and
Power," Scientific American, September 1971, pp. p.
42.
17
UN Department of Economic and Social Affairs,
Statistical Year–book 1969 (New
York: : United Nations., 1970), pp. p.
40.
18
Bert Bolin, "The Carbon
Cycle," Scientific American, September 1970, pp. p.
131.
19Inadvertent Climate Modification, Report of the
Study of Man's Impact on Climate
(Cambridge, Mass.: : MIT
Press., 1971), pp. p. 234.
20
John R. Clark, "Thermal Pollution
and Aquatic Life," Scientific
American, March 1969, pp. p. 18.
21Inadvertent Climate Modification, pp. pp. 151–54.
22
John P. Holdren, "Global Thermal
Pollution," in Global Ecology, ed.
John P. Holdren and Paul R. Ehrlich (New
York: : Harcourt Brace Jovanovich.,
1971), pp. p.
85.
23
Baltimore Gas and Electric Company, "Preliminary Safety Analysis
Page 203
NOTES
Report," quoted in E. P. Ranford et al., "Statement of Concern,"
Environment, September 1969, p. 22.
24
R. A. Wallace, W. Fulkerson, W. D. Shults, and W. S.
Lyons, Mercury in the Environment
(Oak Ridge, Tenn.: : Oak Ridge
Laboratory., 1971).
25Man's Impact on the Global Environment, pp. p. 131.
26
C. C. Patterson and J. D. Salvia, "Lead in the Modern Environment," Scientist
and Citizen, April 1968,
pp. p. 66.
27Second Annual Report of the Council on Environmental
Quality (Washington, DC: :
Government Printing Office., 1971), pp. pp.
110–11.
28
Edward J. Kormandy, Concepts of
Ecology (Englewood Cliffs, NJ: :
Prentice–Hall., 1969), pp. pp.
95–97.
29Second Annual Report of the Council on Environmental
Quality, pp. p. 105.
30 Calculated from average GNP per capita
by means of relationships shown in H. B. Chenery and L.
Taylor, "Development Patterns: Among
Countries and Over Time," Review of
Economics and Statistics 50 (1969):
pp. 391.
31 Calculated from data on metal and
energy consumption in UN Department of Economic and Social
Affairs, Statistical Yearbook
1969.
32
J. J. Spengler, "Values and
Fertility Analysis," Demography
vol. 3 (1966):
pp. 109.
33
Lester B. Lave and Eugene P. Seskin, "Air Pollution and Human Health," Science
vol. 169 (1970):
pp. 723.
34Second Annual Report of the Council on Environmental
Quality, pp. pp.
105–6.
35
Frank W. Notestein, "Zero Population
Growth: What Is It?" Family Planning
Perspectives
vol. 2 (June
1970): pp. 20.
36
Donald J. Bogue, Principles of
Demography (New York: : John
Wiley and Sons., 1969),
pp. p. 828.
37
R. Buckminster Fuller, Comprehensive Design
Strategy, World Resources Inventory, Phase II
(Carbondale, Ill.: : University of
Illinois., 1967), pp. p. 48.
Page 204
NOTES
38
Thomas S. Lovering, "Mineral
Resources from the Land," in Committee on Resources and Man,
Resources and Man (San Francisco,
Calif.: : W. H. Freeman and Company.,
1969), pp. p.
122–23.
39Second Annual Report of the Council on Environmental
Quality, pp. p.
118.
40
Garrett Hardin, "The Cybernetics of
Competition: A Biologist's View of Society," Perspectives in Biology and Medicine
vol. 7 (Autumn
1963): pp. 58, reprinted
in Paul Shepard and Daniel McKinley, eds., The
Subversive Science (Boston: :
Houghton Mifflin., 1969), pp. p.
275.
41
S. R. Sen, Modernizing Indian
Agriculture
vol. vol. 1, Expert Committee on Assessment
and Evaluation (New Delhi: : Ministry of
Food, Agriculture, Community Development, and
Cooperatives., 1969).
42 For an excellent summary of this
problem see Robert d'A. Shaw, Jobs and
Agricultural Development, (Washington,
DC: : Overseas Development Council.,
1970).
43
Richard Critchfield, "It's a
Revolution All Right," Alicia Patterson
Fund paper (New York: : Alicia
Patterson Fund., 1971).
44
Robert d'A. Shaw, Jobs and Agricultural
Development, pp. p. 44.
46
US Bureau of the Census, 1970 Census of
Population and Housing, General Demographic Trends of Metropolitan
Areas, 1960–70 (Washington, DC: :
Government Printing Office., 1971).
47
Garrett Hardin, "The Tragedy of the
Commons," Science
vol. 162 (1968):
pp. 1243.
48
UN Food and Agriculture Organization, The
State of Food and Agriculture (Rome: :
UN Food and Agriculture Organization., 1970), pp. p.
6.
49
John Stuart Mill, Principles of Political
Economy, in The Collected Works of John
Stuart Mill, ed. V. W. Bladen and J. M.
Robson (Toronto: : University
of Toronto Press., 1965),
pp. p. 754.
50
Bertrand Russell, In Praise of Idleness and
Other Essays (London: : Allen
and Unwin., 1935), pp. pp. 16–17.
Page 205
NOTES
51
UN Food and Agriculture Organization,
Provisional Indicative World Plan for Agricultural
Development 2: pp. 490.
52
Herman E. Daly, "Toward a
Stationary–State Economy," in The
Patient Earth, ed. John Harte and Robert
Socolow (New York: : Holt,
Rinehart, and Winston., 1971),
pp. pp. 236–37.
See, for example, "Fellow Americans Keep Out!" Forbes, 1971-06-15 June 15, 1971, pp. p.
22, and The
Ecologist, January 1972.
54
J. Bourgeois–Pichat and Si–Ahmed Taleb,
"Un taux d'acroissement nul pour les pays en voie
de developpement en l'an 2000: Reve ou realite?" Population
vol. 25 (September/October 1970): pp. 957.
55
Commission on Population Growth and the American
Future, An Interim Report to the President and the
Congress (Washington, DC: :
Government Printing Office., 1971).
56
Bernard Berelson, The Population Council
Annual Report, 1970 (New York: :
The Population Council., 1970), pp. p. 19.