THE RESPONSE TO DEFORESTATION AND DESERTIFICATION IN A MODEL OF WEST-AFRICAN MONSOONS

Since Charney proposed his theory on the dynamics of deserts and droug hts in the Sahel [Charney, 1975], there has been significant scientifi c interest in the interaction between vegetation and climate in this r egion. The essence of this interaction is that the atmospheric circula tion, and therefore rainfall, over this region may be sensitive to cha nges in vegetation cover near the desert border. Here we describe simu lations of the West African monsoons with a simple zonally-symmetric m odel. The results suggest that the potential impact of human induced c hange of land cover on regional climate depends critically on the loca tion of the change in vegetation cover. That is, desertification along the border with the Sahara (e.g., in Chad, Niger, Mali and Mauritania ) leaves a relatively minor impact on monsoon circulation and regional rainfall; deforestation along the southern coast of West Africa (e.g. , in Nigeria, Ghana and Ivory Coast) may result in complete collapse o f monsoon circulation, and a significant reduction of regional rainfal l.