Center Paper 18, March 2001

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A succession of scientific and governmental commissions for three decades have come to the same conclusion — that there is a scientific rationale for stabilizing the U.S. population in order to meet environmental goals. While national environmental groups have dramatically changed their stance on U.S. population stabilization, government and scientific bodies have not.

In 1972, the bipartisan Commission on Population Growth and the American Future, chaired by John D. Rockefeller III (hence the Rockefeller Commission), called for stabilizing America’s population. The massive Global 2000 Report to the President, commissioned by Jimmy Carter in 1977 and carried out by an enormous research team headed up by the Council of Environmental Quality and the Department of State, recommended in 1981 that "The United States should....Develop a U.S. national population policy that includes attention to issues such as population stabilization..."² The most recent major finding came in 1996 by President Clinton’s Council on Sustainable Development, established in the aftermath of the 1992 U.N. Conference on Environment and Development in Rio de Janeiro (the "Earth Summit"). The council acknowledged the integral relationship between a stable population and sustainable development, declaring the need to "move toward stabilization of the U.S. population."³

Let us offer our understanding of the core goal of the 1970-era environmental movement:

The environmental movement’s purpose is to preserve, protect and restore the natural and human environment by reducing the total human impact on ecosystems — on watersheds, forests, ambient air basins, wildlife and their habitats, wetlands, estuaries, wilderness, and last but not least, on human health and quality of life. Many of these are issues within localized bio-regions. Others are national in scale or even global, such as marine overfishing, whaling, ocean dumping and the ecological and health effects of atmospheric nuclear testing.

The dominant activism of that time intrinsically included U.S. population stabilization because most environmentalists’ view of environmental quality was deeply shaped by what we will call here the Foundational Formula of the movement. That Formula expressed the movement’s understanding of the problem it was tackling and of how to solve it. The 1990s environmental movement is fundamentally different from the 1970-era movement because it has mostly abandoned that Foundational Formula.

There are several ways of expressing the environmental impacts of humanity. One of the best-known is the I=PAT equation offered by biologist Paul Ehrlich and physicist John Holdren: Environmental Impact (I) equals Population size (P) times Affluence, or consumption per person (A), times Technology, or damage per unit of consumption (T).⁴ The Population and Consumption Task Force of the President’s Council on Sustainable Development expressed it similarly in 1996: "The sum of all human activity, and thus the sum of all environmental, economic and social impacts from human activity, is captured by considering population together with consumption."⁵ The task force also discussed other formulas, such as the POET and PISTOL models, that attempt to make up for the limitations of the I=PAT equation by accounting for other factors such as human organization, information, and space. Still another writer has suggested modifying I=PAT to I=PACT to account for the importance of culture in determining overall environmental impact.⁶

However it was expressed, the Foundational Formula considered total environmental impact on a watershed or any given ecosystem to be the product of two factors:⁷

(1) Individual Impact

(2) Population Size

Individual Impact is the environmental effect of an average individual’s resource consumption from environmental "sources" (e.g. forests, fish stocks, petroleum fields, mineral ores, soils, rivers, aquifers, air) and waste generation into environmental "sinks" (e.g. the atmosphere, ground, aquifers, lakes, oceans). An individual does not have direct control over all of his or her environmental impact. That impact is determined directly by individual voluntary choices about consumption and lifestyle, and indirectly by collective political choices through laws and regulations limiting the impact of producers and consumers (including private and public sectors, individuals and institutions), by the vigor of enforcement of those rules, by available technology to reduce the impact of economic activities, by the financial ability of a society to utilize available technology, and by the methods corporations use to produce and market goods and services.

Population Size is the total number of individuals living in a given bio-region or ecosystem.

Thus, the Total Environmental Impact on the Chesapeake Bay is the result of the Individual Impact of a person living within the larger Chesapeake Bay watershed multiplied by the Population Size in the watershed.

This Formula for a specific ecosystem does not cover everything. For example, air pollution delivered by rain is a major problem for the Chesapeake. One of the sources of air pollution is the string of coal-burning power plants along the Ohio River — well outside the watershed. Thus, part of the quality of the Bay is determined by the per capita electricity consumption and size of populations both inside and outside the watershed that uses electricity from those Ohio River plants. Nonetheless, the overwhelming cause of Bay problems comes from the population within the watershed itself.

Still, just as some impacts to the watershed originate from outside its boundaries, residents of the watershed are also generating effects on other ecosystems in which they don’t live. "Ecological footprint" analysis demonstrates that, as a result of energy and material flows linked to interregional and international trade, individual consumers use or pre-empt ecologically productive land all over the nation and the world.⁸ The average American has an ecological footprint of 12.6 acres (about 12 football fields), compared to 10.6 acres for Canadians, 1.0 for Indians, and 4.4 for the world as a whole. The "footprint" is the area of ecologically productive land needed to supply per capita demand for food, housing, transportation, consumer goods and services, as well as the land area necessary to sequester carbon dioxide emissions (via photosynthesis) from energy use, i.e. fossil fuel combustion. A large population and high per capita consumption give the United States the dubious distinction of possessing the largest ecological footprint in the world. Even at the current population of the U.S. — to say nothing of its projected population — Americans run an ecological deficit, consuming 80 percent more ecologically productive land than we actually have. The difference is made up by our resource and energy (mostly oil) imports and our gargantuan appetite for non-renewable fossil fuels like oil, gas, and coal, which provide us, in effect, with "ghost acreage" from the geologic past.⁹ We are, in other words, consuming our "natural capital" rather than living on "income" — an unsustainable course.

One doesn’t have to work with the Foundational Formula much to realize that changes in the Individual Impact and changes in the Population Size factor have roughly equal power over improving or deteriorating Total Environmental Impact. For example: Increasing the Individual Impact by 30 percent while holding Population Size constant, would have a tremendously deleterious effect on the Bay. And so would increasing Population Size by 30 percent (as Individual Impact is held constant). It really doesn’t matter which one is increased; the Bay feels similar pain.

In the real world, both Individual Impact and Population Size are constantly changing. Thus, the relative magnitude of each factor for an increasing or decreasing Total Environmental Impact must be calculated on a case-by-case basis. Consider the particularly important case of energy consumption — linked directly to a wide range of environmental impacts, such as smog, climate change, acid rain, oil spills, landscape disfigurement, acid mine drainage, radioactive waste, and indirectly to many others. Between 1950 and 1970, the increase in U.S. Population Size accounted for 43 percent of the rise in total U.S. energy consumption, while the increase in Individual Impact was responsible for 57 percent. But between 1970 and 1990 (while environmental groups focused primarily on Individual Impact), increases in Population Size caused 93 percent of the rise in total U.S. consumption.¹⁰

Simply ignoring one of the two factors of the Foundational Formula won’t stop that factor from changing the overall results. (As Aldous Huxley said, "Facts do not cease to exist merely because we choose to ignore them.") A person or group who works to improve the Individual Impact factor while allowing or even supporting deterioration of the Population Size factor may as a matter of intention favor environmental quality. But the effect of that kind of "half-Formula" environmentalism is to retard environmental improvement — and often to actually harm the environment.

This gets to the heart of the difference between the environmental movement of the 1970 era and that of the 1990s. By working on both factors of the environmental Foundational Formula, the early movement had a comprehensive approach to move toward restoration and protection of the environment. The later environmental movement, however, chose a course which allowed the Population Size factor to move ever upward. Every move upward by Population Size ratchets the Total Environmental Impact upward. Thus, the later "half-Formula" environmental movement would forever have to work for lower and lower Individual Impact just to keep the environment from deteriorating further — let alone to achieve restoration — running faster and faster just to stay in place. One needn’t be a physicist to recognize the infeasibility of this as a long-term strategy.

The authors of Beyond the Limits use the example of rising, nonlinear costs of pollution abatement as one moves toward 100 percent removal of pollutants to demonstrate how perpetual growth ultimately undermines environmental protection goals: "If the number of emission sources keeps growing...rising costs will be encountered. It may be affordable to cut pollutants per car in half. But then if the number of cars doubles, it is necessary to cut pollutants per car in half again just to keep the same air quality. Two doublings will require 75 percent pollution abatement. Three doublings will require 87.5 percent, and by then the cost of further abatement is usually prohibitive."¹¹

The 1970-era environmentalists and successive government commissions recognized that correcting the environmental problems of the time through lowering Individual Impact would be a monumental task even if Population Size didn’t grow at all; attempting the corrections while population grew might make the task all but impossible. Consider this simple example:

• Of 10,000 people in a small watershed, each contributes 10 units of pollution. Thus, 100,000 units of Total Environmental Impact are generated.

• To achieve an acceptable, scientifically-based standard of environmental quality, let’s say that Total Environmental Impact must be reduced by 30 percent to 70,000 units of pollution.

• That requires reducing each Individual Impact to 7 units (10,000 people X 7 units = 70,000 units).

• But if the population grows by 30 percent at the same time, all the expense and effort to reduce Per Capita Impact by 30 percent will fail to meet the quality goal. By adding 3,000 people, there are now 13,000 people times 7 units, which equals 91,000 units of pollution — far over the 70,000-unit goal. Will everyone be willing to now undergo still another campaign of reducing their Per Capita Impact 23 percent more just to meet the original goal? (And if there is more increase in Population Size during that campaign, they will have to engage in yet a third round.)¹²

Many analysts in the 1970-era feared that a similar scenario would occur over the next three decades. They knew that if U.S. population continued to grow, even if Total Environmental Impact goals were reached, the government would always have to come back and force ever more Individual Impact cuts on its citizens.

Demographers could project that even if Baby Boomers adopted a below-replacement-level fertility, their very large numbers moving into prime child-bearing years would create a population momentum of around 12 percent growth over the next two decades after 1970. In fact, though, federal increases in immigration resulted in the U.S. population growing by more than 25 percent. (The Census Bureau projects that, under current immigration policies, U.S. population will grow by yet another 50 percent over the next 50 years.)

As the Foundational Formula would predict under such rapid population growth, most U.S. environmental goals set in the 1970s had not been met by 2000. The worsening of the Population Size factor had in many respects negated the improvements in the Individual Impact factor. For instance, America’s lakes and streams were to have become "fishable and swimmable," according to the 1972 Clean Water Act. But after more than half a trillion dollars spent controlling water pollution (costs passed on to consumers and taxpayers), around 40 percent of U.S. surface waters still weren’t fishable and swimmable in the mid-1990s.¹³ The nation has more nitrogen oxide (a smog precursor) and more carbon dioxide (a greenhouse gas) emissions than thirty years ago, more endangered species and fewer wetlands.¹⁴ Regulations on Individual Impact that were thought to be sufficient to meet overall goals had to be tightened much further.

The environmental groups never stopped pressing Congress to lessen Individual Impact on the environment by advocating legislation and regulations targeting private companies, government resource managers, and individual consumers. But through the years, they dropped their advocacy for dealing with the Population Size part of the environmental Formula. And as Congress numerous times debated and approved policies that increased Population Size substantially, the major environmental groups stood silent.

End Notes

¹ This monograph is a significantly expanded version of the authors’ article "The Environmental Movement’s Retreat from Advocating U.S. Population Stabilization (1970-1998): A First Draft of History," which appeared in a winter 2000 special issue of the Journal of Policy History, Vol. 12, No. 1, dedicated to environmental politics and policy from the 1960s to the 1990s (Pennsylvania State University Press).

² "Global Future: Time to Act." 1981. In The Global 2000 Report to the President. A report prepared by the Council on Environmental Quality and Department of State. Gerald O. Barney, study director. p. 11.

³ President’s Council on Sustainable Development. 1996. Sustainable America: A New Consensus for Prosperity, Opportunity, and a Healthy Environment. Washington, D.C.: U.S. Government Printing Office. p. 12. The Council included representatives from a wide range of backgrounds, including environmentalists, population activists, women’s groups, minorities, business leaders, and Cabinet officials. Quote from p. 21.

⁴ Paul R. Ehrlich and John P. Holdren. 1971. "Impact of Population Growth." Science, 171, 1212-1217.

⁵ Population and Consumption Task Force Report. 1996. President’s Council on Sustainable Development. p. 1.

⁶ David F. Durham. 1992. "Perspectives: Cultural Carrying Capacity: I=PACT." Focus, Vol. 2, No. 3. Washington, D.C.: Carrying Capacity Network.

⁷ Like any model of highly complex ecological systems, the Foundational Formula is a simplification of actual causal relationships. Its utility lies in helping us conceptualize and predict (or approximate) causes and effects. One of its key assumptions is that individual impact and population size are independent variables. In reality, however, in certain situations they may be dependent or inter-dependent variables. That is, as population size or density grow, this may exert upward or downward pressure on individual impact via intricate feedback loops.

⁸ Mathis Wackernagel and William Rees. 1996. Our Ecological Footprint: Reducing Human Impact Upon the Earth. Philadelphia: New Society.

⁹ The concept of ghost acreage or "phantom land" is attributed to sociologist William R. Catton, Overshoot: The Ecological Basis of Revolutionary Change (Urbana: University of Illinois Press, 1980). It refers to the fact that the stocks of fossil fuels being consumed today are the products of ancient photosynthesis ("congealed solar energy") that took place in long-gone forests and swamps hundreds of millions of years ago.

¹⁰ John P. Holdren. 1991. "Population and the Energy Problem." Population and Environment, Vol. 12, No. 3.

¹¹ Donella H. Meadows, Dennis L. Meadows, Jorgen Randers. 1992. Beyond the Limits: Confronting Global Collapse, Envisioning a Sustainable Future. Post Mills, Vermont: Chelsea Green. pp. 181-182.

¹² This exercise isn’t entirely academic. Geologist Robert McConnell has calculated that the human "carrying capacity" of the Chesapeake Bay watershed — the number of people it could sustain in perpetuity and still provide a standard of water quality conducive both to human use and healthy populations of fish, shellfish, and submerged aquatic vegetation, given available, affordable water pollution control technologies — had already been exceeded by 1950. "The Human Population Carrying Capacity of Chesapeake Bay: A Preliminary Analysis." Population and Environment, Vol. 16, No. 4, 1995.

¹³ Council on Environmental Quality. 1997. Environmental Quality: 25th Anniversary Report. Washington, D.C.: U.S. Government Printing Office.

¹⁴ Ibid.