Processes and mechanisms of desertification in northern China during the last 30 years,with a special reference to the Hunshandake Sandy Land,eastern Inner Mongolia

Desertification has been widely recognized as one of the most serious environmental problems in China, although its concept and causes are still debated in scientific communities. The semi-arid region in northeastern China, located on northern margin of eastern Asian summer monsoon, is ideal for investigating the processes and mechanisms of desertification because of its very sensitive ecosystem. Using the Hunshandake Sandy Land of eastern Inner Mongolia, a former dormant dunes and wetlands environment, we monitored the variation of the desertified land and the wetlands in order to assess the climatic and human impacts on the processes of desertification. The research methods included digital image processing of LANDSAT data and ground checks. The remote sensing data from the last three decades show that the wetlands were larger in 1975 and 1992 than in 1989 and 2001. The variation of the extension of mobile dunes is in inverse proportion to that of wetlands. The main process of desertification is the reactivation of dormant sand dunes. The changes of wetlands and desertified lands correlate considerably well with the variations of local precipitation and temperature, suggesting that climate might be the key factor triggering desertification in the Hunshandake. In other sandy lands of China, however, human activities might be the key factor causing desertification and land degradation.