Much is left to be done in order to understand the phenomenon of desertification, but the definition commonly accepted since the United Nations Convention on Desertification Control (Rio Summit) is as follows : “the word desertification indicates land degradation in the arid and semi-arid and dry sub-humid zones due to various factors, including climatic and human changes”  (Art 1 Convention on Desertification Control)
This definition discreetly covers the sufferings of millions of Sahelians (desertification affects 70 million people in Africa) facing the following scourges:
The lack of drinking water (source of many waterborne diseases such as Guinea Worm, bilharzias…)

The lack of water for agriculture; some formerly permanent rivers have turned intermittent. The impossibility for the populations to have access to underground water through boreholes and wells, or to stock rain water that runs to rivers then to the Atlantic Ocean due to lack of water reserves, tanks and reservoirs.