ANALYSIS ON DRIVING FACTORS OF DESERTIFICATION IN NORTHERN CHINA: A CASE STUDY OF YANCHI COUNTY
Cold and Arid Regions Environmental and Engineering Research Institute,
Chinese Academy of Sciences,
320 Dong Gang West Road, Lanzhou 730000, P.R. China
Email: email@example.com (Lihua Zhou)
Desertification is one of the most serious environmental and economic problems in the world nowadays. About two-thirds of the countries, one-fifth of the global population and one-fourth of the earth land are now affected by desertification . There are a large scale of areas widely covered by deserts and heavy losses from desertification in Northern China . Understanding the causes of desertification was the key to combat land desertification [3-5]. However, there were considerable debates on the causes of desertification in Northern China [6, 7]. In this paper the driving factors of land desertification had been analyzed on the case of Yanchi County in Ningxia Hui Autonomous Region to understand the reasons of land desertification.
Yanchi County is classical in the agro-pastoral mixed regions in Northern China, with the landscape of alternate distribution of farmland, grassland and sand dunes, where desertification is severe. In this area, the remarkable feature of land desertification is the landscape changing from grassland and farmland to desert (such as sand dunes). Using the Landsat TM imagines of June in 1986, 1995, 2000 and 2005 as the digital sources, the vector and grid landscape maps of distributions of the study area were derived. The dynamic process of landscape pattern had been analyzed on the basis of the software of ArcGIS 9.0.
The results showed that the performance of landscape change is the increase of farmland and the decrease of grassland, and the farmland increase is at the cost of the grassland decrease. At the same time, the fragmentation of grassland landscape is increasing continually, while the farmland is linked up on space with the decreasing landscape fragmentation. The land desertification in this county is severe from 1986 to 1995, but after 1995 it is looking up gradually, and the landscape change is affected more and more by the human activities.
Desertification reversion happened after 2000 for the ecological policies reason. Based on grads analysis of the habitation buffer zone, five landscape elements (farmland, grassland, deserted grassland, woodland and sand) showed the same characteristic in different buffer zones, that was to say that the areas of different landscape elements increased first and then decreased gradually along with the increasing distances to the habitation. In addition, farmland was influenced mostly by the distribution of settlement, and the affected distance of habitation to the farmland (increase of farmland areas) extended gradually.