The dirt on soil loss
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...harvest not only the fruits of their crops but the plants’ stalks and roots, because they can’t afford other fuel for their fires. Their cows and goats, lacking other feed, graze the few plant scraps left in the field. With no organic matter left to decompose and return nutrients to the soil, the land becomes sterile. And with no plant roots left to hold it down, topsoil is whipped away by wind, further reducing soil fertility and even causing breathing problems and lung disease. The depleted soil yields fewer crops, and the cycle of poverty perpetuates itself. “These poor suffering people pass on their suffering to the land,” says Rattan Lal, a professor of soil science at Ohio State University.

Similarly, in the Brazilian rainforest, Amazonian Indians must slash-and-burn trees to plant crops. The bared topsoil quickly washes into the Amazon River. Now, “rock is exposed in places where there was forest,” says Farouk El-Baz, the director of Boston University’s Center for Remote Sensing. The Amazonians, like the farmers in sub-Saharan Africa, must either clear more land or join the estimated 800 million chronically malnourished people in the world.

For wealthy countries like the United States, malnourishment from soil loss is not a major concern yet, but the erosion of soils poisoned by chemicals is. “In developed countries we can put in more fertilizer to bring crop yield up – it’s more of an environmental issue,” says Huang. When eroding soil blows or washes off a field into a nearby river, it may be laden with pesticides, herbicides and fertilizers. The soil muddies clear streams, the fertilizer causes algal blooms, and herbicides and pesticides can kill aquatic animals. Contaminated soil washing down the Mississippi River from Midwestern farms fuels plankton blooms that cause a huge yearly “dead zone” at the mouth of the river, crippling shrimpers.

But farmers are combating soil loss. Soil erosion has been reduced by 40 percent in the United States since 1982. The federal Conservation Reserve Program alone saved twenty million acres of fragile cropland by paying farmers not farm it. Other farmers continue to grow crops on their land but simply stop plowing – a technique known as “no-till” farming - effectively reducing erosion while allowing nutrients to build up in the soil. “I know [no-till] farmers who claim they out produce their neighbors by 15 percent,” say Edward Skidmore, research leader at the USDA...