Strictly speaking, desertification should perhaps be defined as the making of a desert, but there is considerable disagreement amongst scientists over what exactly the term means – the internet has over 100 different definitions. Confusion arises because nobody seems sure of the exact causes of desertification, or what the most important causes are. Chinese scientist Zhu, for instance, said ‘desertification is an environmental degradation process created as a result of the influence of excessive human activities’, defining the process as an extreme form of man-made land degradation, but completely missing the influence of climate change. Scientists are reluctant to put their necks on the line and say exactly why desertification occurs. The situation has not been helped by media reports over the last 30 years that have exaggerated the growth of the Sahara every time there is a new drought in Africa. The expansion and contraction Figure 1: Areas at risk from desertification
SEPTEMBER 2008 576 John Rutter
CAUSES OF DESERTIFICATION
of the world’s arid areas is a situation that has been going on for millennia, but nowadays, with the increasing world population, more people than ever are at risk. The UN has issued perhaps the simplest definition when it says: ‘Desertification is the ... destruction of the biological potential of the land which can ultimately lead to desertlike conditions’. This definition leaves open the causes of desertification and both human and natural processes can be examined for their respective contributions. Africa but, as Figure 1 shows, no populated region of the planet remains unaffected. Desertification was a major cause of mass migration within 1930s USA and is now affecting huge areas of the former Russian republics of central Asia. It has been implicated in the shrinking of the Aral Sea and is also severe in parts of Europe including Portugal and Spain. While evidence on the ground shows that, in certain areas,...