Soil Erosion

The wearing away of the fertile upper layer of soil by water, wind, ice or human activity, faster under farming than under natural cover because tillage breaks soil into finer, more easily carried particles and leaves bare ground exposed between crops. Water and wind together account for roughly 84 percent of the world's land degradation, and global cropland is estimated to lose something on the order of 75 billion tons of soil a year, ten to forty times faster than it naturally forms. The Dust Bowl is this atlas's own worked example of what erosion does at full scale once wind, drought and deep mechanized plowing arrive together.