23 March 2006

Increasing Soil Erosion Threatens World's Food Supply

by Kate Melville

An ecologist from Cornell University reports that soil from the world's croplands is being swept and washed away 10 - 40 times faster than it is being replenished. Astonishingly, an agricultural area the size of Indiana is destroyed every year.

Cornell's David Pimentel lamented that while climate change hogged the headlines, nobody cared much about soil erosion. "Soil erosion is second only to population growth as the biggest environmental problem the world faces," he said. "Yet, the problem, which is growing ever more critical, is being ignored, because who gets excited about dirt?"

People should start getting concerned now, according to Pimentel, particularly with demand for food and other agricultural products continuing to soar. His figures indicate that the United States is losing soil 10 times faster than the natural replenishment rate, while China and India are losing soil 30 - 40 times faster. Pimentel says that as a result of erosion over the past 40 years, 30 percent of the world's arable land has become unproductive.

His study, appearing in the Journal of the Environment, Development and Sustainability, noted that erosion does not only impact arable land. Around 60 percent of eroded soil ends up in rivers, streams and lakes, making waterways more prone to flooding and to contamination from fertilizers and pesticides. Erosion also reduces the ability of the soil to store water and support plant growth, thereby reducing its ability to support biodiversity.

"Erosion is a slow and insidious process that nickels and dimes you to death. One rainstorm can wash away 1 mm of dirt. It doesn't sound like much, but when you consider a hectare, it would take 13 tons of topsoil - or 20 years if left to natural processes - to replace that loss," Pimentel explained. "And that kind of loss occurs year after year by wind and rain around the world."

But stopping soil erosion is easy, he said. "Controlling soil erosion is really quite simple. The soil can be protected with cover crops when the land is not being used to grow crops." Other ways he cited to lessen erosion include reducing the need for people in developing countries to clear forests for agriculture, overgraze their cattle and remove crop residues for cooking fuel.

Source: Cornell University