“For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled.”

Richard Feynman


Recent Developments in Environmental Sciences – Ehrlich

Paul R. Ehrlich, Bing Professor of Population Studies and

President, Center for Conservation Biology

Stanford University

The speech was part of the ceremonies presenting Ehrlich with the $125,000

H. P. Heineken Prize for Sciences by the Royal Netherlands Academy of Arts

and Sciences. Sept. 25, 1998

The past decade has been a critical one for the environmental sciences in three changing areas: continuing growth in the scale of the human enterprise, what is happening to the biosphere as a result of that growth, and how the community of environmental scientists is approaching the problems of achieving sustainability. As a result, it has been both an exciting and worrying time for ecologists like myself. In this brief paper, I want to deal with each of these three areas of change in turn.

The scale of the human enterprise, as measured by energy use, has increased some 20-fold since 1850. 1 The environmental impact (I) of that scale can be viewed in terms of the I=PAT identity, where P is the size of the Population, A is Affluence (or consumption), and T is a measure of how environmentally malign are the Technologies and the economic, social, political and political arrangements involved in servicing the consmption. 2 Because the A and T factors are very difficult to sort out from available statistics, it is customary to substitute per capita energy use for A x T in the identity. In the past decade, the scale of the enterprise has increased about 5 percent, despite one quite positive development in the factors affecting that scale.

That development has been a small but significant decline in fertility rates in many nations of the world. For example, in 1988 the global population stood at 5.13 billion, the rate of natural increase for the world was 1,7 percent, and the total fertility rate (TFR)3 was 3.6. In mid-1998 the population had grown to 5.93 billion, but the growth rate had declined to 1.4 percent, and the TFR was down to 2.9. Most important, in the rich countries, where overconsumption per individual puts enormous pressure on human life-support systems, average TFR dropped from 1.9 to 1.6, and their populations had virtually stopped growing. At the same time the TFR in the developing world (excluding China) declined from 4.9 to 3,8 — more than a full child per family. 4

All of this is a start in the right direction, but even on the population front the world still has a long way to go. The decline in the P factor in that decade simply moved the projected date at which the population will pass 8 billion from 2019 to 2024. To put this in context, you must remember that estimates of the long-term carrying capacity of Earth with relatively optimistic assumptions about consumption, technologies, and equity (A x T), are in the vicinity of two billion people.5 Today’s population cannot be sustained on the “interest” generated by natural ecosystems, but is consuming its vast supply of natural capital — especially deep, rich agricultural soils, “fossil” groundwater, and biodiversity — accumulated over centuries to eons. In some places soils, which are generated on a time scale of centimeters per century are disappearing at rates of centimeters per year. Some aquifers are being depleted at dozens of times their recharge rates, and we have embarked on the greatest extinction episode in 65 million years.

Despite all this, the drop in vital rates in Europe has been a cause not for rejoicing but for hand-wringing among those who are ecologically illiterate, hand-wringing that has been echoed in the American press.6 The last time Europeans panicked over demographic decline was during the depression of the 1930s. But Europe’s population expansion has been unprecedented: despite huge waves of emigration to the Western Hemisphere, the population of Europe quadrupled between 1750 and 1950. Even since the depression, Europe has added on the order of 75 million people — more than the combined present populations of the United Kingdom, Sweden and Denmark. Now growth has finally stopped and a slow decline is beginning — a cause for celebration on this vastly overpopulated continent. This European decline is especially cheering because of the extremely high consumption rates and huge “ecological footprint” 7 of European nations.

Outside of the population statistics, on the A x T front, most of the trends over thc past decade have been negative, however. Consumption in many rich nations continues to grow, much of it reasonably classed as “overconsumption” in comparison to the material goods available to the average human being. The most serious population growth in the world is occurring in the United States, the third most populous nation in the world. The U.S.A. still has a natural increase of 0.6 percent, a TFR of 2.0, and a growth rate (thanks largely to immigration) of over one percent. Most importantly, it has an extremely high level of consumption per person — on the order of ten to thirty times that of people in developing nations. Thus the addition of each person to the American population, whether by birth or immigration, is many times the disaster for the world as a birth in Kenya or Bangladesh. Despite this, there is no sign of any official policy for population limitation in the nation in which, from a global viewpoint, it is most needed. And the United States is even further from a program of consumption control, which is even more badly needed. 8

Most developing nations, in contrast, have recognized their population problems and taken steps to deal with them. But the A x T element in those nations can be a source of serious problems as well. In the rich sectors of otherwise poor economies, like that of China, patterns of consumption are converging on those of the developed nations. In China, for example, increased meat consumption has been signaled by a 70 percent increase in the percentage of total available grain fed to livestock between 1985-87 and 1995-97. 9 China has already surpassed U.S. consumption per capita of both pork and eggs. 10 Indeed, in special cases, the pressures generated by countries like China can often exceed those of the West and Japan. Hong Kong, for instance, is a major consumer of the living resources of the sea. Some 6 million residents devour 300,000 tons of seafood (about 50 kg per person) annually. They are partly responsible for the destruction of the world’s coral reefs from dynamite and cyanide fishing. Live reef fishes are in enormous demand — Hong Kong Chinese wishing to display their affluence will pay up to 1000 Hong Kong dollars (US $130) for a plate of lips from a large Napoleon wrasse (a reef fish), 11 One can easily imagine the impacts on natural systems of increasing affluence in proportionately small but numerically large subpopulations in China and other developing countries. The spread of American consumerism is a global threat, and the prospect of ever greater disparities in living standards not only between nations but within nations bodes ill for the environment, which in most circumstances benefits as equity increases. 12

Thirty years ago, timing ways to slow and halt population growth were near the top of the agenda of the environmental science community. It is now slowly dawning on us that curbing runaway consumption may be even more difficult. And socio-economic and political constraints make it very difficult to institute desirable changes in the mix of technologies used to supply the consumption. In my view, for example, it would be wise to reduce human exposure to a wide array of hormone-mimicking synthetic organic chemicals, 13 but economic forces such as plastics manufacturers and users powerfully resist such a reduction. Similarly, political power purchased by the coal industry in Australia has kept that nation on the fossil fuel treadmill, even though there has been strong public sentiment to switch to solar and other more environmentally benign technologies in order to slow global warming. Much the same can be said of the United States. Indeed, the only major success in the technological arena in the last ten years has been the implementation of the 1987 Montreal ozone protocol to limit the use of freons. Achieving that was relatively simple, since a “smoking gun” was in hand in the form of the ozone hole, and the relatively few corporations involved could make even bigger profits manufacturing chlorofluorocarbon substitutes. Limiting the flux of greenhouse gases from energy consumption, deforestation, and agriculture will be orders of magnitude more difficult.

Now let’s turn to the second topic — what’s happening to the biosphere. What can be said about the past decade’s increases hi our understanding of the consequences of expansion of the human enterprise? Perhaps most dramatic has been the growing evidence of anthropogenic climate disruption. The 1995 report of the scientific committee of the Intergovernmental Panel on Climate Change (IPCC), cautiously stated that the warming measured over the last century “is unlikely to be entirely natural in origin.., the balance of evidence suggests that there is a discernable human influence on global climate. ” 14 Despite a determined campaign of denial by certain elements of industry and a small group of dissident scientists, 15 it has become increasingly clear that the IPCC is correct. One key piece of scientific evidence that had been considered anomalous, satellite observations showing a cooling trend in the troposphere, turned out to be due to the failure of scientists interpreting the satellite data to take into account the steady lowering of the satellite’s altitude caused by atmospheric drag. When corrections were made for this, satellite and surface data appeared in agreement. Top atmospheric scientists wrote that: “warming trends of both the surface and troposphere are now sufficiently clear that the issue should no longer be whether global warming is occurring, but what is the rate of warming.” 16 There are, of course, many suspicious signs of rapid change in the climate itself, from an increased frequency of extreme weather events in North America 17 to a widespread meltdown in Alaska where glaciers are in rapid retreat, long-standing permafrost is melting, and widespread forest-death, caused by interacting stresses from permafrost soils being converted to swamps and newly abundant insect pests attacking already weakened trees. 18

Arguably equally important is thc growing documentation by biologists of the degree to which human activities are modifying the biosphere — and broad acceptance of the conclusion that human influences arc increasingly disrupting the functioning of ecosystems. 19 For instance, humanity has now approximately doubled the annual natural rate of addition of nitrogen to the terrestrial nitrogen cycle, creating potentially serious problems for the maintenance of soil fertility, accelerating losses of biodiversity, contributing to acid deposition, and enhancing the greenhouse effect. 20 Humanity has recently been calculated to bc using over half of the reasonably accessible freshwater runoff, 21 and some 43 percent of Earth’s terrestrial vegetated surface has lost some of its capacity to supply humanity with benefits — overall about a 10 percent reduction in potential value — as a result of human actions. 22

The last decade has also seen an accelerating loss of populations and species of other organisms that are involved in supplying crucial natural services to society, as natural areas are more and more displaced by human activities. Thus tropical forest destruction continues throughout most of the developing world. 23 Destruction of oceanic fisheries has come to wide public attention in the same period, as stock after stock is overfished, 24 and often the physical/biological infrastructure that supports the fisheries is destroyed. There are also growing signs that the toxification of the planet is causing serious effects on wildlife and human health through the release of hormone-mimicking synthetic organic chemicals, although demonstrating the causal links is difficult. 25 And ecosystem services that are essential for maintaining agricultural production, such as pollination, 26 are faltering in many areas.

Third, what are environmental scientists doing that is new? Their activities constitute the best news outside of the lowering of birth rates. Building on advances in basic ecology over the past half-century, they are making important gains in understanding the significance of the negative environmental trends, finding ways to counter them, and helping to move humanity onto a path to sustainability. One outstanding example is the substantial progress that has been made in analyzing the relationship between the loss of biodiversity and the delivery of essential ecosystem services. Increasingly, research by community ecologists like David Hooper, John Lawton, Shahid Naeem, David Tilman, and Peter Vitousek indicates that the long-term stability of the services will depend on maintaining a mix of species to provide redundancy in each of various roles organisms play in natural and agricultural ecosystems. 27 Another gain has been the development, under the leadership of population biologist Gretchen Daily, of the new field of “countryside biogeography,” which seeks ways of maintaining critical elements of biodiversity in human-dominated landscapes. This is an especially important field, since every cubic centimeter of the biosphere has already been altered by humanity to some degree, and most areas have been modified dramatically from their state before humanity became a significant ecological force. Since it is clear that relatively few parts of the planet can be kept even relatively undisturbed, special efforts must be made to maintain critical elements of biodiversity — not just species but, just as importantly, populations 28 of other organisms.

Perhaps most heartening of all is the rapidly growing cooperation of economists and ecologists in efforts to find policy instruments to help preserve humanity’s natural capital. 29 While the trend traces to the early efforts of Heineken Laureate Herman Daly, beginning in the 1960s, the last decade has seen an explosion of activity. At Stanford University, weekly seminars now bring together economists and ecologists (as well as engineers, historians, members of the faculties of law and business, and others) to discuss the environmental dimensions of the human predicament. I now frequently share postdoctoral students with Larry Goulder of Stanford’s Department of Economics. The Beijer Institute of Ecological Economics has had an extremely active program of discussion and research in this area, and has produced a long series of important publications bringing the two disciplines together. 30 And the International Society of Ecological Economics has grown enormously after starting its journal, Ecological Economics. just a decade ago.

Related to this is a growing realization among my colleagues that one cannot depend on working with governments alone to solve the growing environmental crisis. Instead the emphasis is shifting to recruiting the business community into the struggle to achieve a sustainable society. While there is a long way to go in that process, there are encouraging signs such as thc Natural Step program, begun by Dr. Karl-Henrick Robert in Sweden, and the writings of businessmen Paul Hawken and Stephan Schmidheiny. 31 Some businesses have already demonstrated that it is possible to make more money operating in a manner that is ecologically sound than in one that ignores the impact of operations on the environment. One outstanding example is Interface, a company that (under the inspired leadership of CEO Ray Anderson) supplies commercial carpeting on a rental basis. When the carpet is worn, Interface replaces it and completely recycles the old material, rather than dumping it into a landfill. The company is enormously successful, grossing more than $1 billion annually. Through such examples, other corporations may learn that they can do well while doing good.

It is important to recognize, however, that just converting business to a powerful force for environmental quality cannot solve our predicament as long as the scale of the human enterprise continues to grow. What is needed now is to involve people in solving local end regional environmental problems and in encouraging their governments to cooperate more in seeking resolution of global problems. Business leaders have both heavy responsibilities and great opportunities in these areas — and they have a great deal of expertise in putting theory into practice. They and their children and grandchildren are fully as dependent for their lives on the services supplied by natural ecosystems as everyone else. They depend on those systems to make the air breathable, to supply freshwater and prevent floods, to dispose of their wastes, arid to support the agricultural enterprise that nourishes them by generating and maintaining soils and providing free pest control and pollination services. And perhaps more than anyone else, they are experts in the critical area of consumption — and in a position to help curb the growth of the energy use and material throughput involved. Technological changes such as electronic communications instead of travel and substitution of environmentally more benign energy sources for the dominant fossil fuel technologies of today can help — but changes in lifestyle and human ambitions will be needed here also. The business community also has the political power to lead a transition toward a sustainable global society — one with a smaller population supplied with both necessities and substantial luxuries. I urge businessmen everywhere to learn about the current environmental situation and then accept the challenge. And scientists, politicians, and ordinary citizens should do the same. Nothing less is at stake than the fate of human civilization.


1. J.P. Holdrin, 1991, Population and the energy problem. Population and Environment 12:231-235, and personal communication (1998).

2. J. Holdrin and P. Ehrlich, 1974, Human population and the global environment, American Scientist 62:282-292; P. Ehrlich and A. Ehrlich, 1990, The Population Explosion, Simon and Schuster, Now York.

3. Roughly the average completed family size.

4. Demographic statistics from Population Reference Bureau, World Population Data Sheet,1988 and 1998.

5. G.C. Daily, A.H, Ehrlich, and A. Ehrlich, 1994, Optimum human population size. Population and Environment 15:469-475.

6. On July 10, 1998, a long, incompetent article appeared in the New York Times was entitled “Population Implosion Worries a Graying Europe.” Charles Krauthammer followed up in the Washington Post with another of his exquisitely ignorant environmental columns on the same general theme (July 17). Its headline said it all: “Saved by immigrants the U.S. fertility rate is barely at replacement level.”

7. M. Wackernagel and W. Rees, 1996, Our Ecological Footprint: Reducing Human Impact on Earth. New Society Publishers, Gabriola Island BC.

8. P.R. Ehrlich, et al., 1997, No middle way on the environment, The Atlantic Monthly 280 (6):98-104.

9. World Resources Institute, 1998, World Resources 1998-99, Oxford University Press, Oxford.

10. L. R. Brown, 1998, The future of growth. In L.R. Brown, et al., State of the World, 1998, W.W. Norton, New York.

11. C. Safina, 1997, Song for the Blue Ocean. Henry Holt and Company, New York.

12. G. Daily and P. Ehrlich, 1996. Socioeconomic equity, sustainability, and Earth’s carrying capacity, Ecological Applications 6(4):991-1001.

13. A steady flow of recent information has made ever more pertinent the 1996 warning of T. Colborn, D. Dumanoski, and J.P. Myers in Our Stolen Future, Dutton, New York.

14. Intergovernmental Panel on Climate Change (IPCC) 1996. Climate Change 1995, Summary for Policymakers, Working Group I, pp. 10-11

15. Although there has been some genuine scientific debate, much of this campaign has been outright disinformation (see P. Ehrlich and A. Ehrlich, 1996, Betrayal of Science and Reason: How Anti-environmental Rhetoric Threatens Our Future Island Press, Washington, DC; R. Gelbspan, 1997, The Heat is On: The High Stakes Battle over Earth’s Threatened Climate, Addison-Wesley, Reading, MA. The most recent incident involved the circulation fake reprint designed to look like an article that had been published in the Proceedings of the National Academy of Sciences, U.S.A.

16. J. Hansen, M. Sato, R. Ruedy, A. Lacis, and J. Glascoe, 1998, Global climate data and models: a reconciliation. Science 81:930-932.

17. T.R. Karl and R.W. Knight, 1998, Secular trends of precipitation amount, frequency, and intensity in the USA. Bulletin of the American Meteorological Society 79:231-242.

18. W. Stevens, 1998, As Alaska reeks,’ scientists consider the reasons why. New York Times, 18 August.

19. P. Vitousek, et al., 1997. Human domination of Earth’s ecosystems. Science 277:494-499.

20. P. Vitousek, H. Mooney, J. Lubchenco, and J. Melillo, 1997. Human alteration of the global nitrogen cycle: sources and consequence. Ecological Applications 7:737-750

21. S. Postel, G. Daily, and P. Ehrlich, 1996. Human appropriation of renewable freshwater. Science 271:785-788.

22. G. Daily, 1995. Restoring value to the world’s degraded lands. Science 269:350-3.54.

23. N. Myers, 1996. The world’s forests: problems and potentials. Environmental Conservation 23:156-168.

24. D. Pauly, 1998. Fishing down marine food webs. Science 279:860-863.

25. E.g., J. Toppari, et al., Male reproductive health and environmental xenoestrogens, Environmental Perspectives 104 (suppl. 4):741-803.

26. E.g., Buckmann and O. Nabhah, 1996, The Forgotten Pollinators, Island Press, Washington, DC; G. Nabhan and S. Buchmann, 1997, Services provided by pollinators. In O. Daily (ed.), Nature’s Services, Island Press, Washington, DC, pp. 133-150.

27 For a popular summary see Bob Holmes, 1998, Life support, New Scientist, 15 August, pp. 30-34.

28. Ehrlich and G. Dally, 1993, Population extinction and saving biodiversity, Ambio 22:2-3; J. Hughes, G. Daily, and P. Ehrlich, 1997, Population diversity: its extent and extinction, Science 278:689-692.

29. P. Ehrlich, 1997, World of Wounds: Ecologists and the Human Dilemma, Ecology Institute, Oldendorf/Luhe, Germany, chapter 5.

30. E.g., K. Arrow, et al., 1995, Economic growth, canting capacity, and the environment, Science 268:520-52l.

31. P. Hawken, 1993, The Ecology of Commerce: A Declaration of Sustainability. HarperCollins, New York; S. Schmidheiny, 1992, Changing Course: A Global Perspective on Development and the Environment, MIT Press, Cambridge, MA.