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STANFORD -- Attempts to feed an exploding population could prove disastrously self-defeating, Paul Ehrlich, Stanford University's Bing Professor of Population Studies, told the American Association for the Advancement of Science (AAAS) Friday, Feb. 7.

In expanding food production, humanity is depleting irreplaceable parts of its life support systems - fertile soils, groundwater and a diversity of living species - Ehrlich said in a featured speech at the AAAS annual meeting in Chicago. Expending this natural capital accelerates environmental degradation and increases the risk of future starvation.

"The potential seriousness of the population-food- environment problem is such that it must quickly be elevated to the top of the human agenda," Ehrlich said. "There is no way that a business-as-usual approach to the ecological and social dimensions of the problem can possibly lead to anything but disaster."

Ehrlich told an AAAS seminar on feeding the world that "each year, farmers must feed more than 90 million additional people, with roughly 24 billion fewer tons of topsoil, trillions of gallons less groundwater, and faltering ecosystem services." His data was based on policy research conducted with Anne Ehrlich and Gretchen Daily of the Center for Conservation Biology at Stanford.

Almost 200 million people have died of starvation or hunger-related disease in the past quarter century, and more than a billion are hungry today, Ehrlich said. However, he said, the ultimate biophysical limits to food production are not the critical issue. In theory, global harvests could be doubled or tripled in the short term.

"The critical issue is the environmental cost that will need to be paid for increasing food production, especially if long- term sustainability is to be sacrificed," he said.

Expansion of farming can intensify environmental degradation. For example, deforestation to create more cropland and pasture and the spread of paddy rice cultivation contribute to global warming and rapid climate change. That, Ehrlich said, "may be the single greatest threat to the human food supply."

Other environmental impacts will make it increasingly difficult for food production to keep pace with population growth: losses of farmland to urban and other uses, diminishing returns from fertilizer use, declines of genetic variability of crops, toxic air pollution, acid precipitation and the threat of ozone depletion.

"Equally significant in the real world are social, political and economic constraints on productivity rooted in such things as inequitable distribution of land, lack of access to inputs and farm credit, and political neglect of the agricultural sectors of many poor economies," Ehrlich said.

"All of these factors interact. Poor people have high population-growth rates. Additional people add to stresses on environmental systems. Stress on those systems in turn reduces the ability of agricultural systems to provide food."

Ehrlich and his colleagues took exception to "absurd notions such as that the world's food resources will feed 40 billion people" - eight times the present human population. Such estimates, he said, are based on the productivity of an acre of Iowa cornfield, multiplied by the acres of flat land on the planet. They do not consider that few lands can be as productive as Iowa's, that soil erosion, climate change and rising sea levels may damage productive land, and that even Iowa's future productivity is in doubt.



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