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New UN soil survey: the dirt on erosion.

Since World War II, more than 3 billion acres of agricultural land -- an area larger than China and India combined -- have been damaged by human actions and may prove costly or impossible to reclaim. This and related findings presented in a new United Nations report "confirm our worst fears about the degree to which soils are eroding and being degraded around the planet," says James G. Speth, president of the World Resources Institute (WRI) in Washington, D.C. It topsoil erosion continues at post-World War II rates, feeding an exploding world population could prove extremely difficult, he says.

"Each year the world's farmers are trying to feed 92 million more people with 24 billion tons less topsoil," comments agricultural economist Lester R. Brown, president of the Worldwatch Institute in Washington, D.C. "You don't have to have a Ph.D. in agronomy to understand that those two trends can't both continue indefinitely."

WRI released the UN-sponsored survey -- the first ever to chart soil health globally -- last week. The findings indicate that nearly 22 million acres of the world's land can no longer support vegetation and may have little hope of recovery. Another 740 million acres will require a restoration effort larger than most developing nations could organize. Some 2.3 billion acres more -- an area about the size of the United States -- require major and costly reclamation efforts, such as installation of drainage ditches.

In addition to erosion from wind and water, the survey mapped soil degradation from chemical sources, such as excessive levels of salt or pollution, and from physical sources, such as livestock or heavy machinery. The UN team of roughly 200 analysts attributes:

* 35 percent of soil erosion to livestock overgrazing, a problem that appears most widespread in Africa and Oceania. Not only can animals strip away plant cover, leaving topsoils erodible, but their trampling can also compact soil, reducing its ability to hold moisture.

* 30 percent of soil damage to deforestation. Although deforestation is occurring most rapidly in Asia, the survey finds it most prevalent in South America.

* 20 percent of soil degradation to harmful agricultural practices, such as overfertilization or ignoring fallow periods. In North America, the survey fingers poor agricultural practices as the prominent cause of soil damage.

Parts of Africa, Asia and South America have been especially hard hit by soil degradation -- a problem that may be tied to poverty, according to Allen L. Hammond, WRI's program director for resource information. "Without economic growth, [the poor] have no choice but to destroy their own environment in the search for daily sustenance," Hammond says.

Brown notes that many villages can no longer grow enough food to subsist, let alone to make a profit. "You see villages that used to be inhabited but no longer are because the topsoil has washed away. When the soil goes, the people eventually have to go."

Meanwhile, in the United States, 25 percent of croplands are eroding faster than they can be preserved, according to estimates by the U.S. Soil Conservation Service.

Restoring badly damaged topsoil may require more resources than some nations can muster, says Speth. This June, the UN Conference on Environment and Development will convene in Rio de Janeiro to discuss global policies -- and possible treaties -- on soil protection, desertification and deforestation. Through these discussions, "the opportunity is at hand to do something to address, rectify and remedy these appalling trends," says Speth.
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Title Annotation:United Nations report
Author:Raloff, Janet
Publication:Science News
Date:Apr 4, 1992
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