Dust Bowl Writ Large?

Climate change and endangered species may dominate the headlines about the planet's health, but a researcher who has been studying soil erosion warns of a similar crisis beneath our feet. The news is worrisome, he says, but a worldwide catastrophe is not inevitable--if agricultural nations quickly adopt the best new farming practices.

Each year, the world's agricultural land loses, on average, about 1 millimeter of topsoil. That might not seem like much, but it takes 10 years for the soil to replace that loss, and any topsoil loss at all makes the land less able to support crops without expensive infusions of chemical fertilizers. To combat erosion's effects, some farmers have adopted less harmful tilling methods, but the vast majority has resisted the best practice of all: no-till farming, which replaces the plow with mechanical seed drills that barely disturb the surface of the soil (ScienceNOW, 7 August). At present, only 7% of the planet's agricultural land receives no-till farming, most of it in North America and South America.

To determine how fast soil is being lost and whether anything can be done to stop or reverse the trend, geomorphologist David Montgomery of the University of Washington, Seattle, has been analyzing the scientific literature on erosion. In the September issue of GSA Today, published by the Geological Society of America, Montgomery draws two conclusions. First, conventional agriculture, which is still practiced widely, creates soil-erosion rates that exceed soil-production rates by up to several orders of magnitude. Second, the application of no-till and organic farming--which naturally builds topsoil--as well as crop rotation, can sustain agricultural productivity while maintaining the fertility of soils indefinitely.

"The longevity of our present society depends not so much on intrinsic limitations to the lifetime of societies, but on the way we treat the land," says Montgomery, the author of Dirt: The Erosion of Civilizations. One bright spot, he says, is that the United States and Canada, two of the world's biggest food producers, have adopted soil-conservation farming methods to a great extent. It's "one of the few areas of environmental concern where we are ahead of the curve," Montgomery says. Still, he's concerned about the promotion of corn for biofuels. If not done with care, he says, the trend "risks reintroducing very erosive agricultural methods," thereby switching "an energy system based on mining oil for one based on mining soil."

Soil scientist John Reganold of Washington State University in Pullman calls Montgomery's conclusions "right on" and seconds his warnings about erosion. We're already feeling the effects of agricultural soil loss, he says, especially on hillsides. Grain yields, for example, could be significantly higher if soil erosion rates were cut. Along with no-till methods, Reganold foresees improved soil conservation with organic farming systems and via the development of perennial grains, which do not require reseeding each year.

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