土壤流失是人类未来面临的压力最大的难题之一,象美国这样一个先进的工业国,在过去的两千年中至少损失了农地表土的30％。有人在1935年作过估计,有将近四千万公顷农地因土壤流失而遭毁坏,另外还有四千万公顷农地失去了50％～100％的表土。因此,到1935年止,就有八千万公顷农地因土壤流失而遭受严重影响或导致毁坏.近来,因土壤流失,以占美国农地2/3的私人所有的农地里每年要损失32亿吨土壤。 Soil erosion is one of the most pressing challenges for mankind in the future. An advanced industrialized nation such as the United States has lost at least 30% of its surface area over the past two millennia. It was estimated in 1935 that nearly 40 million hectares of farmland had been destroyed by soil erosion and that 40 million hectares of farmland had lost 50-100% of the topsoil. As a result, 80 million hectares of farmland have been severely affected or destroyed by the loss of soil by 1935. Recently, there has been an annual loss due to soil erosion to privately-owned agricultural land, which accounts for two-thirds of U.S. farmland 3.2 billion tons of soil.