Environmental Sustainability
Albert A. Bartlett
University Of Colorado, Boulder, 80309-0390
(303) 492-7016 or 492-6952

Text of an invited paper presented at the annual meeting of the American Association Of Physics Teachers meeting in Denver, Colorado, August 16, 1997

Let me express my sincere thanks and admiration for PROFESSOR JANE JACKSON and the others who have worked with her in order to bring some of these crucial environmental topics into our physics classrooms. Many, many, thanks !


Sustainability is what it’s all about.

We need to know the meaning of sustainability. An understanding of exponential arithmetic is a prerequisite to an understanding of the problems of achieving sustainability. I assume that you are all well acquainted with the arithmetic of exponential growth, and in particular with the fact that steady growth can give astronomically large numbers in a modest period of time. To understand sustainability we turn first to the most widely quoted definition, which is for sustainable development:

  • Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
  • The World Commission on Environment and Development,
    Gro Harlem Brundtland
    Our Common Future, Oxford University Press, 1987

    We need a more detailed understanding of the meaning of sustainability than we can gain from this one statement. First: Sustainability has to mean, "for a time period long compared to a human lifetime." Second: Exponential arithmetic shows that steady growth of numbers of things for long periods of time is impossible.

    An Oxymoron

    The inescapable observation that follows from these two facts is that the term "sustainable growth" is an oxymoron !

    Now let’s look at a quotation from our national leaders:

  • We will renew America’s commitment to leave our children a better nation -- a nation whose air, water, and land are unspoiled, whose natural beauty is undimmed, and whose leadership for sustainable global growth is unsurpassed.
  • (Emphasis has been added)
    William J. Clinton, Al Gore
    Putting People First: How We Can All Change America.
    Times Books, New York City, 1992, pg. 94-95

    Our leaders’ lack of understanding of sustainability is a major problem.

    Let’s look at some facts that point to the urgency of thinking seriously about sustainability.

    Global warming:

    There is a growing scientific consensus that human activities are now having observable effects on the global climate.

    Newsweek for august 11, 1997, pg. 62, reports that "average annual air temperatures on the Antarctic peninsula have climbed 5 degrees Fahrenheit over the last 50 years, 10 times faster than the global rate.

    "Average midwinter temperatures there are up 9 degrees.

    "The cause could be natural climate fluctuations. or it could be global warming induced by the heat-trapping "greenhouse gases" emitted into the atmosphere."

    The Ozone Hole:

    The destruction of ozone in the high atmosphere allows more ultra-violet light to reach the surface of the earth where it can have serious biological effects. We must recognize that we are now embarked on a global experiment whose outcome is unknown. And more frightening, it is not even known if the global response to human activities is reversible.

    Are we walking along reversibly on level ground, or are we jumping irreversibly off a cliff ?


    The Worldwatch Institute reports that annual global per capita production of grain has dropped from 346 kilograms per person in 1984 to 313 kilograms per person in 1996. This is a drop of 9.5 % in the last 8 years!

    In an observation that should interest physicists, David and Marcia Pimentel estimate that in the united states, three units of fossil fuel energy are needed to produce one unit of food energy.

    Oceanic Fisheries:

    The annual oceanic fish catch stopped growing in 1989, and many of the world’s major fishing resources are now seriously depleted.

    Fresh water:

    A report in January 1997 from Stockholm indicated that by the year 2025, two-thirds of the world’s peoples will suffer from water shortages. The rate of growth of the use of fresh water is twice the rate of growth of world population.


    My own analysis suggests that approximately three quarters (75%) of the recoverable petroleum in the 50 states has been consumed and we in the U.S. are now coasting downhill on the remaining 25 % of the petroleum. We in the U.S. now import more than 50 % of our petroleum.

    Further, my analysis, based on geological estimates of the total world resource of petroleum, suggests that world petroleum production will peak around the year 2004 and thereafter will start its inevitable decline toward zero.

    Think what it will mean to have declining world production of petroleum and an increasing world population that aspires to have increasing per capita consumption of petroleum.

    In 1996 the average world per capita production of oil was about 1.7 liters per person per day, and falling.

    Population Growth

    All of these problems are caused by population growth. None of these problems can be "solved" if population growth continues.

    Physics Is A Luxury

    Physicists tend to worry about physics, while leaving the problems of society, and in particular the problems of sustainability, to others. Physicists have a tremendous stake in the global future.

    Compared to survival, physics is a luxury that can exist only in an stable society.

    The immediate consequence of overpopulation is the decline of democracy, followed by political instability, which seems to be on the increase in all parts of the world. In an unstable society, physics will be an early casualty. Can you imagine trying to do physics in the former Yugoslovia ?

    Reaching The Student

    I sense that the topics that are discussed in our texts, and probably in our classes are becoming more and more theoretical (and interesting to physicists) but are becoming less and less relevant, in the sense that these topics have little relation to the world in which our students will live and function.

    Topics such as heat and thermodynamics are given less emphasis, or are omitted, in order to gain time to talk about exotic advanced concepts.

    I think the most crucial problem is in the introductory physics classes at all levels in institutions ranging from high schools to the large universities. The majority of the students in these introductory classes will probably never take another physics course. We have only one chance to help these students.

    Do we want to frustrate these students by exposing them to some of the vocabulary of quantum mechanics, or do we want to try to give them a solid background in the fundamental elementary topics that are essential to an understanding of the world of their everyday experiences ?

    The key to sustainability lies in understanding the simple classical science of the everyday Newtonian world.

    Is there anywhere in the large introductory courses where we can reach large numbers of students with discussions of the problems of growing populations and sustainability? This question gains great urgency from the fact that we live in a world that worships growth and that talks enthusiastically about "sustainable growth," which is a clear impossibility.

    Worship of Growth

    This optimistic exclusion of reality exists not only at the national level; it also exists in the communities where we live and work.

    Here in Boulder, Colorado we have the Boulder County Health Communities Initiative. This has consisted of a series of well organized monthly "town meetings" in which concerned people from all walks of life assemble regularly to talk about the problems that we face in Boulder County; problems such as overcrowding of schools, traffic congestion, air pollution, excessive regulation and control, high and rising taxes, uncivil behavior, etc.

    The leaders of the initiative often speak of working to achieve sustainability. All of these problems are caused by population growth. None of these problems can be solved as long as population growth continues

    Yet in the monthly meetings, I am the only person who speaks up to call attention to the causal role of population growth in all of these problems, and to point out that if we are serious about sustainability, the first thing we must do is to stop the population growth. When I raise the issue, almost everyone, including the leaders, listens politely and then goes on as though nothing had been said.

    We know we are facing limits; we deny this critical fact. Yet the population continues to grow, and physicists who have the ability to understand the problems, by and large don’t speak out in our classrooms or in the public that we serve. We pride ourselves on our critical thinking, yet most of us fail to apply our critical thinking abilities to the contemporary problems of society.

    Five Examples

    Let’s look at five examples of widely accepted arguments that are routinely offered by the promoters of population growth in our communities. These arguments can be proven wrong by the simplest of analysis. We all have encountered this kind of non-critical thinking at the local level where we as individuals can speak up and point out the fallacies of these arguments

    First: Was there ever a politician who did not love to say, "we have to create new jobs?" Now think critically, and you will see that creating jobs in your community increases the number of people in your community who are out of work.

    Here’s how it happens:

    The equilibrium unemployment rate is about 5 %. When new jobs are created in your community, the unemployment rate might drop perhaps to 3 %. But then new people move into the community to take the jobs and restore the unemployment rate to the equilibrium value of 5 %.

    But this is 5 % of a larger population, so the number of people out of work in your community has increased. You can’t have a region of permanent low unemployment in the U.S. any more than you can have a region of permanent low pressure in a closed container of gas.

    One can say with confidence that there are twice as many people out of work in Denver today, as there were when Denver had half of its present population. And you can say with confidence, that for every 100 new jobs created in your community, the number of unemployed people in your community will increase by approximately 5 .

    Second: "We have to attract more people and more factories in order to get more municipal tax revenue - - that is, to broaden the tax base."

    Of course, more people result in more tax income to the community, but they also result in more infrastructure demands on the tax revenue.The demands always grow faster than the revenue. Indeed, using national data, I have estimated that on the average, the per capita annual municipal taxes vary as

    (Municipal Population)^ 0.3

    The fundamental rule is: "Population growth never pays for itself!" Even with more people paying taxes, each person’s municipal taxes have to go up to pay for growth. A recent study in Oregon indicated that every new home built in Oregon generates public costs of about $26,000 !

    Third: How often have you heard it said that we have to upgrade our two-lane highways to giant multi-lane freeways, "in order to reduce air pollution?"

    Of course, if you drive a given distance nonstop, the pollution generated by your car is less than if you drive the same distance stop-and-go. But the new presence of a multi-lane freeway generates enormous new volumes of traffic, not previously present, whose added pollution overwhelms the small reduction in pollution per each vehicle generates per unit of distance driven. Ultimately the large freeways are congested and drivers experience much larger traffic jams than they had on the earlier two-lane roads.

    The complete and unequivocal proof of the fallacy of the argument lies in the observation that if building freeways reduced air pollution, Los Angeles would have negative air pollution, whatever that is!

    Fourth: "Allowing bigger and heavier trucks on our highways will be more efficient and will reduce costs."

    This is the favorite refrain of the trucking lobbies, and right now congress is under pressure from the truck lobbies to allow increases in the lengths and weights of trucks on our highways.

    What are the facts? The highway damage per kilometer as a function of the mass of the vehicle goes up as something like the 3rd or higher power of the mass of the vehicle! So it has been said that essentially all highway damage is due to heavy trucks.

    Allowing heavier trucks saves money for the trucking company, but simultaneously it generates enormous cost increases for the taxpayers who must pay for repair of the damaged highways and for the repair of the damage to cars that have been hurt by being driven on the damaged highways. Allowing heavier trucks does reduce the truckers’ costs. it does so by shifting these costs to the public.

    Fifth: "Improved design of our new subdivisions will help save the environment"

    This improved design is often called "smart growth." This is crazy! Building new subdivisions on open land destroys the environment of the open land, whether the new subdivisions are well-designed, or poorly designed.

    The well-designed subdivisions may consume less land per person than the poorly designed ones. But in either case, the new subdivision is destroying the environment. The rate of destruction with "smart growth" is less than the rate with "dumb growth."

    So smart growth is better than dumb growth, but it’s like buying a ticket on the Titanic. You can be smart and go first class or you can be dumb and go steerage

    but the end result is the same.

    Municipal Mythology

    So, here are five everyday examples of non-critical thinking that are foisted off onto the American public every day in every part of the country. These are part of my collection of "municipal mythology." These fallacies are part of the great efforts to promote population growth and in so doing, to move the country farther from the goal of sustainability.

    Role of Technology

    Now let’s ask, "what role have science and technology played in the creation of the problems of overpopulation ?"

    Let me demonstrate that science and technology are largely responsible for the population problems and hence for all of the problems that we are facing!

    1) Medical sciences have reduced death rates from disease and accidents. This contributes very much to the growth of populations.

    2) Technology makes it possible for more people to live in areas that earlier supported only small populations. For example, two hundred years ago, this "Great American Desert" of the western U.S., supported perhaps a million native Americans. Now, thanks to engineering and technology we may have a hundred million people living here.

    The contribution of medical advances to overpopulation is very clear. The contribution of engineering and technology needs to be examined. As populations grew, cities grew even more rapidly. The problems of supply and distribution of water and other utilities became difficult. Engineers "solved" the problems by developing safe systems for gathering, treating and distributing water.

    As cities grew, the disposal of wastes became a serious problem. Engineers "solved" the problem by developing sanitary sewers, treatment plants, and systems for collecting and disposing of trash.

    When cities became crowded, engineers invented skyscrapers which will let even more people crowd into the center cities. Engineers then had to invent transportation systems to get people in and out of the cities so that they can fill the skyscrapers.

    We build networks of urban freeways and big bridges so that people can live residentially in distant agricultural land, displacing the farmers, and then the people can commute long distances into the downtown skyscrapers to work.

    As the farms are displaced farther from the centers of the cities, we depend increasingly on petroleum-based transportation technologies to bring us our food. I believe I have read that the average distance traveled by food from farm to the consumer is now something like 1200 miles.

    The whole goal of engineering might be summed in two statements.

    1. Engineering makes it possible to crowd more people into our cities and countryside, and
    2. Engineering makes possible the gadgets and gizmos that increase our per capita consumption of resources.

    Both of these are justified as contributions to "the better life." We individually are the beneficiaries of the wonderful advances made in medicine. By themselves, these benefits result in population growth. Yet we have taken these benefits and have ignored the responsibility that goes with the benefits, that is, humans have an obligation to lower fertility so that there would be a stable population.

    If we had a stable population, a larger fraction of the world’s people would be able to experience the benefits of the better life that comes with technology. In some primitive cultures, the people understood the concept of "carrying capacity." but the concept became lost when the people were "educated" and the cultures were modernized.

    For example, the natives on bikini island in the pacific ocean numbered about 120 when the U.S. Navy moved them out in 1946 for the weapons tests. The population had probably not deviated very much from 120 persons for the entire period of human habitation of the island. The natives understood the concept of the carrying capacity of the environment that was immediately available to them.

    But then the natives were thrust into our society. They were moved to another island and a supply ship was sent in every month or so. The supply ship removed the necessity of living within the carrying capacity of the island. Their population began to expand, and now they number perhaps 1500, and this present population could never return to its ancestral homeland and survive without a supply ship. Their forced encounter with civilization transformed their society from being sustainable to being unsustainable.

    But not all native populations understood the concept of carrying capacity and the limits of resources. Archaeologists are reconstructing the history of the people who lived on easter island, where the magnificent stone monoliths stand. These giant stones were, quarried, carved and moved to their present positions in some period long ago.

    Initially, the Easter Island was heavily forested. Large trees provided food, fiber, and building materials for deep sea canoes, for operating the stone quarries, for moving and erecting the monoliths and for shelters. Then the day came when the islanders cut the last large tree.

    Very quickly everything degenerated, the dwindling resources led to warfare and decline. All the knowledge and technology of the earlier times was quickly lost. Even in that primitive situation, it is hard to imagine that people could fail see that the tree resource was expiring, so people could take remedial actions to preserve the resource that was essential to the whole society.

    But look around today. Look at our colleagues in physics.

    How many physicists today are even bothering to look at the problems of the high rates of consumption of non-renewable resources? Our education system has failed to educate us about the most important facts that we need to know in order to have a sustainable society. We have textbooks on environmental science that give good treatments of all manner of minutiae, but omit serious discussion of population growth as the most important environmental problem.

    Even worse than these failures, scientists and technologists have given people the belief that science and technology can solve all of our resource problems, forever.

    To some degree this is understandable.

    After all, in physics and engineering, much of the emphasis of our courses is on the solving of problems. This belief that science and technology can solve all of our problems gives rise to the non-scientists such as Julian Simon who recently wrote:

  • "Technology exists now to produce in virtually inexhaustible quantities just about all of the products made by nature - - foodstuffs, oil, even pearls and diamonds...

    "We have in our hands now -- actually in our libraries -- the technology to feed clothe and supply energy to an ever-growing population for the next 7 billion years...

    "Even if no new knowledge were ever gained ... we would be able to go on increasing our population forever."

  • This quotation is not from scribblings on a restroom wall, this is the front page story in the official publication of one of the most influential high-level think tanks in Washington, D.C.! People in Washington love to hear this sort of thing: they don’t want to worry about the real problems of population. They welcome a Ph.D. "scholar" who says that there is no need to worry.

    Critical thinking

    With regard to experts, it is important that we and our students remember a fundamental law: For every Ph.D. there is an equal and opposite Ph.D. Or, as a president of Harvard once said, "there’s a Harvard man on the wrong side of every argument."

    Somehow, critical thinking about everyday things has disappeared from American education. We have an obligation to help restore critical thinking to American education.

    Kenneth Boulding was an economist, but he was also a profound and independent thinker. Ponder Boulding’s three theorems on population.

    Kenneth Boulding’s First Theorem

    The Dismal Theorem

  • If the only ultimate check on the growth of population is misery, then the population will grow until it is miserable enough to stop its growth.
  • Kenneth Boulding’s Second Theorem

    The Utterly Dismal Theorem

  • Any technical improvement can only relieve misery for a while, for so long as misery is the only check on population, the [technical] improvement will enable population to grow, and will soon enable more people to live in misery than before. the final result of [technical] improvements therefore, is to increase the equilibrium population which is to increase the sum total of human misery.
  • Kenneth Boulding’s Third Theorem

    The Moderately Cheerful Form Of The Dismal Theorem

  • If something else, other than misery and starvation, can be found which will keep a prosperous population in check, the population does not have to grow until it is miserable and starves, and it can be stably prosperous.
  • Boulding clearly understood the population problem. A broad-brush condemnation of our failure in higher education was provided recently by Peter Drucker who said, (Science, July 18, 1997, pg. 311)

    "I consider the American research university of the last 40 years to be a failure. the great educational needs of tomorrow are not on the research side but on the learning side."

    Failure of Education

    He predicted that in the future the bulk of learning will not occur on the traditional residential university campuses, but through some form of distance learning. The research universities, which Drucker says have failed, are the model which is emumlated by most of higher education, including the secondary schools.

    In Scientific American for august 1997, pg. 16, "Bruce M. Alberts, president of the national academy of sciences says that scientists: ‘have to think more broadly about what they respect.’

  • "He bemoans ‘intellectual snobbery’ that values only work that probes the deepest mysteries.

    "Alberts maintains that ‘the future stability of the world’ could depend on whether researchers can, for instance, provide the world’s poor with rewarding ways to live that do not entail moving to overcrowded cities."

  • The concept of sustainability addresses the fundamental question of the survival of society. Education for sustainability must start in our classrooms. We have the obligation to work with the large numbers of students in our introductory classes, to lead them to explore the meaning of sustainability, even though sustainability is not now in our textbooks or curricula.

    Laws of Sustainability

    Here are the laws of sustainability as I worked them out for an article that was published in 1994.

    First law:

    Population growth and/or growth in the rates of consumption of resources cannot be sustained.

    Second law:

    The larger the population of a society, and / or the larger its rates of consumption of resources, the more difficult it will be to transform the society to the condition of sustainability.

    Third law:

    The response time of populations to changes in the total fertility rate is the length of time people live, or approximately fifty to seventy years. (the consequence of this is called "population momentum.")

    Fourth law:

    The size of a population that can be sustained (the carrying capacity) and the average standard of living of the population are inversely related to one another.

    Fifth law:

    Sustainability requires that the size of the population be less than or equal to the carrying capacity of the ecosystem for the desired standard of living.

    Sixth law:

    The benefits of population growth and growth in the rates of consumption of resources accrue to a few individuals; the costs of population growth and growth in the rates of consumption of resources are borne by all of society.

    Seventh law:

    Growth in the rate of consumption of a non-renewable resource such as a fossil fuel, causes a dramatic decrease in the life-expectancy of the resource.

    Eighth law:

    The time of expiration of non-renewable resources can be postponed, possibly for a very long time, by

    1. technological improvements in the efficiency with which the resources are recovered and used,
    2. using the resources in accord with a program of "sustained availability"
    3. recycling
    4. the use of substitute resources.

    Ninth law:

    When large efforts are made to improve the efficiently with which resources are used, the resulting savings are easily and completely wiped out by the added resource needs that arise as a consequence of modest increases in population.

    Tenth law:

    The benefits of large efforts to preserve the environment are easily canceled by the added demands on the environment that result from small increases in human population.

    Eleventh law:

    When rates of pollution exceed the natural cleansing capacity of the ecosystems, it is easier to pollute than it is to clean up the environment.

    Twelfth law: (Eric Sevareid’s law)

    "The chief cause of problems is solutions."

    Thirteenth law:

    Humans will always be dependent on agriculture.

    1. Supermarkets alone are not sufficient.
    2. The central task in sustainable agriculture is to preserve agricultural land.

    Fourteenth law:

    If, for whatever reason, humans fail to stop population growth, and growth in the rates of consumption, nature will stop these growths.

    Fifteenth law:

    Starving people do not care about sustainability. if sustainability is to be achieved, the necessary leadership and resources must be supplied by people who are not starving.

    Sixteenth law:

    The addition of the word "sustainable" to our vocabulary, to our reports, programs, papers, and to the names of our academic institutes and research programs, is not sufficient to ensure that our society becomes sustainable.

    Seventeenth law:

    Extinction is forever !

    Explosion Of Anti-knowledge

    In an interview with Bill Moyers, Isaac Asimov said,

    "Democracy cannot survive overpopulation. Human dignity cannot survive overpopulation. Convenience and decency cannot survive overpopulation. As you put more and more people into the world the Value of life not only declines, it disappears. It doesn’t matter if someone dies. The more people there are, the less one person matters."

    In our education for survival of society we must focus on:

    The explosion of knowledge and communication has been accompanied by an explosion of anti-knowledge. If students leave our classes and are unable to separate sense from nonsense, they will be of little value to a society that is going to face enormous real problems. It may be that no other academic discipline is seriously or realistically concerned with education for sustainability.

    In which case, it's up to us.