The relative role of climatic and human factors in desertification in semiarid China

Many previous studies have attributed desertification in semiarid China over the past 50 years to over-grazing, over-reclamation, land misuse, and population pressures. The present study, which covers the period from the 1950s to the early 2000s, includes an analysis of proxies for human activity, such as the area of arable land, number of livestock, and population size, and of variations in climatic indices, such as precipitation, evaporation, temperature, frequency of sand-driving winds, and drift potential, to evaluate the key contributors to desertification or rehabilitation in this region. We demonstrate that although human activities and anthropogenic pressures have both promoted desertification, two climatic indices (drift potential and the frequency of sand-driving winds) had a much stronger effect than has been appreciated in previous research. The impact of human activity on environmental change may thus have been overestimated in previous studies. (c) 2005 Elsevier Ltd. All rights reserved.