Man-made deserts: desertization processes and threats

摘要

Desertization is defined as the irreversible extension of desert land forms and landscapes to areas where they did not occur in a recent past. Such extension does not result from a would-be increasing aridity as there is no evidence of any global long-term trends in rainfall in arm lands since the period of instrumental record (ca. 150 years). The 0.5 deg C of global temperature increase over the past 100 years remains well within the range of historical fluctuations. The creation of man-made deserts is actually the result of long-lasting mismanagement of natural resources under the pressure of excessive human and livestock populations. Such land abuse may drive ecosystems beyond their resilience potential for recovery. The causes and mechanisms of arid land degradation pertain to direct and indirect activities, processes, and phenomena, which are not necessarily linked to aridity or drought. Causes, severity, and extent of desertization are quantified from various sources. The potential for biological recovery is analyzed and the ways and means to achieve rehabilitation assessed. The conclusion addresses the issue of the future of desertization under the additional threat of an increased aridity that might occur assuming a possible global temperature increase of the planet, triggered by atmospheric pollution. It tries to quantify the possible increase of aridity under various scenarios.