Introduction

People have lived in arid lands since pre-historic times. There have always been deserts, and there have always been droughts. Only in comparatively recent years, as Cloudsley-Thompson (1986) justly notes, has the man-desert interaction led to such dramatic social and environmental consequences as those that were witnessed during the Sahel droughts of 1968-73 and 1982-85. These droughts caused the collapse of the entire agricultural base of five countries (Mauritania, Upper Volta, Mal~ Niger and Chad), already among the poorest nations in the world, and severe damage to the agricultural base of two others: Senegal and Gambia (UNCOD 1977). By some estimations, between 100,000 and 250,000 died as a result of the drought. In addition, some refugees never returned to their homelands (Kates et al. 1977)