Drylands cover 41 percent of the Earth's land surface. Of that area, desertification has rendered 20 percent unfit for human use, and an additional 70 percent remains vulnerable. According to the United Nations, desertification is degrading soil quality in 110 countries, directly impacting 250 million people and threatening a billion more, all without creating a single new desert. "True deserts have evolved for millions of years," says Exequiel Ezcurra, research director for the San Diego Natural History Museum. "When you get degradation in Oklahoma, you don't get a desert popping up, you just get barren soil."
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