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World's Land Slipping in Quality

Emily Sohn, Discovery News

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Their findings, published in the journal Soil Use and Management, revealed that 24 percent of land worldwide is degraded because of things people are doing. Worst off were African countries south of the equator, Southeast Asia and south China.

About 20 percent of the degraded regions were on crop land, and about 40 percent were in forests. Surprisingly, whether a forest was designated as protected or not made no difference. The scientists were also surprised to find that the Amazon didn't make much of a dent on the map.

Especially concerning, Dent said, was that the areas highlighted in the new study had almost no overlap with the areas highlighted in the 1991 study. That suggests that degradation is cumulative, and that it's getting progressively worse.

One and a half billion people currently live in degraded areas. And as soils decline, people reach a point where they can't grow enough food to feed themselves. They move on, leaving the dead land behind.

"Once it has happened, it becomes very expensive to correct that situation," said Hari Eswaran, a soil scientist with the United States Department of Agriculture's Natural Resources Conservation Service in Washington, D.C. "But we can prevent it by helping these people to practice more sustainable forms of agriculture."

Choosing appropriate crops, for example, maintaining them correctly, and reducing erosion are all strategies that can help people survive, Eswaran said.

Those strategies can also help the environment. The scientists calculated that all of the vegetation that has been lost from the world's degraded land would have removed an extra billion tons of carbon out of the atmosphere if it were still healthy and green.

Journal: Soil Use and Management

HowStuffWorks.com: Deforestation

Discovery Earth Pub