ABSTRACT
The arid and semi-arid agro-ecological zones of Africa are not a marginal fringe but contain from 36 to 43 per cent of its area, depending on the definition used (Figure 7.1). The semiarid zone – where crop and livestock production are about equally important – accommodates at least 28 per cent of the population of tropical Africa on 18 per cent of its surface, with 27 per cent of its ruminant livestock (Jahnke, 1982). As vacant land was, until recently, still abundant, the drylands have witnessed unprecedented surges in their human populations. The conservation of natural resources and achievement of sustainable livelihoods in the drylands therefore deserve a prominent place in discussions of African development policy.
