The geography of semi-arid lands

Abstract

Semi-arid lands were at times during the last 20000 years more humid and at other times more arid than at present, with important consequences for the soil and water resources of the present day. These lands were the scene of the beginnings of pastoralism, the cultivation of cereals, and urban living between 10 000 and 5000 years ago. The environment has always been attractive to man but it is liable to deteriorate towards desert with long-lasting consequences. Development possibilities diversify according to environmental conditions which vary from place to place and also according to the economic and other characteristics of the States in which these lands are situated. The States can be regarded as falling into four categories: there are on the one hand wealthy countries - either industrialized or rich in minerals; on the other hand there are poor countries - some with land outside the arid zone as yet not fully developed, others with no land of this kind. In response to the differences in economic opportunity, migratory movements are taking place, notably from the impoverished semi-arid regions to the towns, particularly those in the petroleum-producing states.