Change and Instability in the Desert Environment
Deserts cover approximately one-third of the Earth’s land surface, constitute one of the world’s major ecosystems and provide a significant contribution to the global economy. They provide at least a fifth of the world’s food supplies, over half of the world’s production of precious and semi-precious minerals, and a substantial proportion of oil and natural gas reserves. They are also areas of very rapid technological and demographic change, with, for example, many instances of quickly developing urbanisation. Many of the great deserts are of considerable antiquity. For example, recent studies of aeolian sediments in dated ocean cores have shown that materials have been removed by deflation from arid surfaces in the vicinity of the present Sahara since the Cretaceous and Tertiary. However, during the course of these millions of years the deserts have undergone a series of major changes at a variety of scales. The purpose of this chapter is to explore the nature, causes and consequences of this variability, and to examine some of the ways in which it relates to human activities.
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