From Envirowiki

Desertification is the process of turning a landscape into a desert. It can happen naturally though local climate changes, or through invasive herbivorous species (goats are especially good at this), or through bad human land management.

The Middle East is thought to have been largely made desert through agricultural practices, including land clearing, irrigation, and goat farming. Similarly, Easter Island was cleared (although remained green, due to coastal humidity) for human timber use.