Desertification assessments in the Hexi corridor of northern China’s Gansu Province by remote sensing

Abstract

The Hexi corridor region lies in the arid and semiarid regions of Gansu Province, China. The sensitive ecological environment has undergone severe desertification caused by natural environmental change and unsustainable exploitation of the region. Remote sensing and GIS are being used to study desertification in this region. In this paper, we used Landsat TM and HJ data between June and August in 2000, 2005, and 2010 to analyze the spatial and temporal patterns of the desertification using five indices: the modified soil-adjusted vegetation index, fractional vegetation cover, the surface albedo, land surface temperature, and the temperature–vegetation drought index. We normalized the indicators, determined their weights, and defined five grades of desertification: none, light, moderate, severe, and extremely severe. We found that desertification in the Hexi corridor covered more than 76 % of the total land area; the total area of desertified land was 22.02 × 104, 21.22 × 104, and 21.06 × 104 km2 in 2000, 2005, and 2010, respectively, which amounted to 79.8, 76.9, and 76.3 % of the total area. In both periods, the most spatial changes in desertification showed a stability or reversal of desertification from 2000 to 2005 and from 2005 to 2010. From 2000 to 2010, the area in which desertification reversed (1.00 × 104 km2) was a little more than the area of newly desertified land (0.96 × 104 km2). The reversal of desertification mainly involved a change from severely and moderately desertified land to non-desertified land. Natural factor and human activity controlled the desertification process, but the reversal of desertification mainly resulted from human activity.