Underfoot and overlooked - worldwide soil erosion needs attention

AMONG the many environmental problems the world faces, soil erosion is moving rapidly toward the top of the list. This year's State of the World review by the Worldwatch Institute, for example, puts the annual global soil loss at some 26 billion tons. It cites a 1982 survey, based on at least a million readings, that indicates the United States alone loses something like 2 billion tons a year.

While environmental specialists can agree there is massive soil erosion, however, there is no consensus as to how soon this is likely to seriously curtail the world food supply. There simply are not enough good data to define clearly what is happening to soil in even industrialized countries, let alone the industrially developing world. What is increasingly seen as a leading environmental problem has yet to receive top priority research attention.

This was evident during a discussion at the recent annual meeting of the American Association for the Advancement of Science in Boston.

Some studies have put United States annual farm productivity losses to soil erosion at about $1 billion. Cornell University agricultural scientist David Pimentel said such estimates are far too low. They should be more like $43 billion a year in terms of loss of long-term productivity.

Some farmers could be losing as much as 30 percent of their inherent soil productivity in a single year because of erosion, he said. Such loss now is masked by irrigation and addition of chemical fertilizers. But Pimentel considers this a palliative that does not restore the soil and only postpones an inevitable productivity loss.

Analyst Pierre Crosson, on the other hand, echoed conclusions of a 1986 National Academy of Sciences study in saying that productivity of US farmers is not threatened. Instead, the main damage from soil erosion is outside farmland in silting waterways, polluting water supplies, and other effects.

It was obvious that, given the present lack of knowledge, one can frame plausible arguments to support quite different conclusions about the ravages of erosion by selective use of what data there are. The two speakers easily agreed that more research is badly needed to better define the problem both within the United States and in the world generally.

There seems to be no doubt that unwise land use, rather than drought or other adverse weather, is the main cause of erosion. Deforestation, overly intensive farming, and farming of marginal lands are some of the worst practices. But simply identifying such culprits, as has been done many times, does not solve the soil erosion problem. It needs to be defined region by region and country by country so that both the degree of threat and suitable solutions can be worked out for each locale.

Pimentel calls soil erosion the ``No. 1 environmental problem of the world.'' It should have comparable priority in both the research plans of individual countries and the cooperative international environmental studies in which they participate.

A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.