Verdant land can become desert as a result of drought, increased erosion due to land-clearing, poor farming techniques, overgrazing of livestock, and drainage of surface and underground water for crop irrigation and household and industrial use.
Even an existing desert can become more of a wasteland when ecological balances change. The Sonoran and Chihuahuan Deserts of the U.S. Southwest and Mexico have become increasingly barren as native plants and wildlife have been diminished by several factors, including the depletion of groundwater by human activity.
Perhaps the most frightening aspect of desertification is that it tends to be what scientists call a runaway phenomenon. Once it begins in a particular area, it is almost impossible to stop, and it cannot be reversed within a human lifetime.