The Silent Crisis

Alan Kuper


The great majority of people around the world never ask, “ Is the world overpopulated?” They don’t know what it might mean to them, any more than members of an endangered species rapidly losing habitat to human encroachment can comprehend the cause of their predicament.

That the human population of the world is over six billion, that it might double in this century, means little to most Americans. Few know the population of the world, of their nation, or of the state where they reside. They don’t know why they should. No authority has ever told them it was important to know those numbers, except to say that, in general, the more people the better. No one has ever told them that, unless people only replace themselves, unless couples on average have no more than two children, population will grow ever faster, compounding like money in the bank to unimaginably large numbers. If the U.S. population grows due to immigration, however rapidly, that has—until very recently—been regarded as beneficial as well.

Most Americans don’t know that today’s human numbers are a very recent phenomenon—that as recently as 1930, in their grandparents’ youth, world population was barely two billion, and U.S. population was less than half of what it is today. People and institutions have not adjusted to the sweeping new challenge of accelerating growth in human numbers.

Infinite growth is an impossibility in a world of finite resources. As economist Kenneth Boulding declared, “Anyone who believes exponential growth can go on forever in a finite world is either a madman or an economist.”

Human numbers and activity have become quite literally a geologic force, manifesting themselves through global warming, which is already having harmful effects. High mountain glaciers and snowfields are no longer reliable sources of spring river flows, so that water for agriculture does not arrive at the time and in the quantities most needed. In Arctic regions, structures built atop permafrost are collapsing. Polar ice is melting, releasing freshwater flows that may alter the great ocean circulations, changing climates, temperatures, and agricultural production over vast areas. Environmental problems are always of our own making, but never before on such a scale.

Once this is recognized, many thoughtful observers will conclude that humans have a responsibility to reduce their impact on the environment as described by the Holdren-Ehrlich Formula:


The formula (also known as “eye-Pat”) states that human impact (I) on environments can be understood as the product of population (P) times the affluence (A) of the society, or average consumption per capita, times the level of environmental harm done by the technologies employed (T).1

eye-Pat has been called “the E=mc2 of the modern environmental movement,” as both formulas describe processes that can end in cataclysmic explosions.2

To reduce human impact on the environment, the short-term remedy is to reduce consumption, particularly forms of consumption that have especially harmful effects. To reduce impact in the long term, to achieve an environment that can be sustainable far into the future, reducing consumption is not enough. It is also necessary to reduce population to sustainable levels. A sustainable economy is defined as one that provides for present needs without jeopardizing its ability to supply generations far into the future in much the same way.Science and technology enthusiasts, particularly if they are long on blind faith and short on understanding of fundamental limits, tend to be complacent—to shrug and say, “They’ll think of something” to fix overpopulation. But overpopulation is already doing irreparable harm, in particular by driving the continuing extinction of other species. The largest die-off since the extinction of the dinosaurs is now in progress, all of it human-caused. Population growth and extinctions go hand in hand: it is estimated that more than five hundred species have gone extinct in the United States alone in the last two centuries. More than one thousand are currently listed as threatened or endangered.4 The principal cause is “loss of habitat,” a euphemism for human encroachment.

Sadly, all of us living in the “real world,” including leaders in politics, business, and industry are inclined to ignore, rationalize, deny, or simply postpone action as long as possi-ble—this despite widespread knowledge that changes wrought by overpopulation will likely have an irreversible negative impact. But they realize that reducing population and con-sumption to sustainable levels will require massive economic and social restructuring throughout society.5

The American public is not demanding government action to achieve reduced consumption, greater efficiency in energy use, or reductions in population. The media sometimes pres-ent conservation in a favorable light, but the idea of gradually reducing the U.S. population seldom receives attention, unless it is presented as a threat to the economy. Almost never do the media portray reduction in human numbers as a beneficial step away from the impossibility of endless population growth.6

As population and consumption grow, stocks of nonrenewable resources dwindle. Obviously this cannot continue. Since change is inevitable, the public should be informed of the possible benefits of a gradual transition to long-term sustainability.7 The benefits of achieving a significantly smaller U.S. population might include:

•Reduced demand for scarce resources.•Full employment.•More direct democracy.

• A cleaner, healthier environment with fewer costly environmental problems.

•Less congestion, crowding, and sprawl.

•More stable communities and institutions.

• More set-asides of natural areas for wildlife habitat and recreation.

• Fewer costly military interventions overseas to secure access to foreign resources.

With populations gradually shrinking in Japan and in countries in Europe, notably Germany and Italy, perhaps by mid-century we’ll know how population reduction plays out. To let human numbers become—or remain—a geologic force constitutes a great wrong.


1. P.R. Ehrlich and J.P. Holdren, “Impact of Population Growth,” Science 171, pp. 1212–17 (1974).

2. James Surowiecki, “The Financial Page—Waste Away,” The New Yorker, May 6, 2002.

3. Gro Harlem Brundtland, Our Common Future: Report of the 1987 World Commission on Environment & Development (New York: United Nations, 1987).

4. Mark W. Nowak, Immigration and U.S. Population Growth—An Environmental Perspective (Washington D.C.: Negative Population Growth, Inc., 1997), p.7.

5. Interestingly, the less developed the society, the greater its potential to live sustainably, albeit not richly. In fact the best examples are the few Stone Age peoples who may still exist. Primarily hunter-gatherers, they live generation after generation without significantly altering the habitat on which they depend. They accomplish this principally by living in small isolated groups and deliberately maintaining constant numbers. But any outside contact threatens their existence.

6. For a discussion of benefits, see Lindsey Grant, Too Many People: The Case for Reversing Growth (Santa Ana, Calif.: Seven Locks Press, 2000). See especially his Chapter 13, “The European Example.”

7. See Herman E. Daly, Beyond Growth: The Economics of Sustainable Development” (Boston: Beacon Press, 1996).

Recognizing Our Limits

At the conclusion of his book The Living Planet David Attenborough writes:

We have to recognize that the old vision of a world in which human beings played a relatively minor part is done and finished. The notion that an ever-bountiful nature, lying beyond man’s habitations and influence, will always supply his wants, no matter how much he takes from it or how he maltreats it, is false. We can no longer rely on providence to maintain the delicate interconnected communities of animals and plants on which we depend. Our success in controlling our environment, that we first achieved 10.000 years ago in the Middle East, has now reached its culmination. We now, whether we want to or not, materially influence every part of the globe.”8

—from David Attenborough, Our Living Planet (Boston, Toronto: Little, Brown, and Company, 1984), p. 308.

Alan Kuper is the founder and president of CUSP (Comprehensive U.S. Sustainable Population) and a former professor and physicist. He was active in the Sierra Club for thirty years and was the recipient of two club awards.

Alan Kuper

Alan Kuper is the founder and president of CUSP (Comprehensive U.S. Sustainable Population) and a former professor and physicist. He was active in the Sierra Club for thirty years and was the recipient of two club awards.