Encroaching Desertification

Hundreds of thousands of people -- some of them the world's poorest -- will be displaced in the next 30 years as the globe's deserts expand, according to the latest report from the U.N.'s Millennium Ecosystem Assessment. Climate change is likely to intensify droughts, heat waves, and floods in "drylands," which comprise 41 percent of the earth's land surface and are home to 2.1 billion people. Other human factors also contribute to desertification, including unsustainable farming and irrigation practices, overgrazing, and population overload. And the impacts are global: Huge dust storms in the Gobi and Sahara deserts are causing respiratory problems in North America and hurting coral reefs in the Caribbean. To fight desertification, the U.N. recommends a $100 billion investment in improving management of crops and irrigation, shifting local economies to more sustainable bases like ecotourism and fish farming, and developing clean energy sources in arid zones.