The disastrous drought in the years 1968-1973 prompted the world community to examine the state of arid territories and to formulate strategies to combat desertification. The Rio Summit in 1992 defined desertification as the degradation of soils in arid, semi-arid and dry subtropical zones under the impact of various factors, including climatic change and human activities. In effect, when arid zones are affected by ever-increasing soil degradation, reducing reserves of productive soils, an environment similar to desert is created, hence the term desertification.