Sandy desertification is the main ecological problem the Otindag Sandy Land at present. In order to reveal the process of land degradation, especially the latest situation of sandy desertification, a method integrating remote sensing, Geographic Information System (GIS) and field survey was employed to build a sandy desertification dataset for analysis. Remote sensing images included the Landsat Thematic Mapper (TM) in 1987, the Enhanced Thematic Mapper plus (ETM+) in 2000, and the Charge Coupled Device Camera (CCD) of China-Brazil Earth Resource Satellite (CBERS) in 2006. Five land-cover classes, including active sand dunes, fixed sand dunes, semi-fixed sand dunes, inter-dune grassland and wetlands, were identified.
Results showed that the Otindag Sandy Land has been suffering sandy desertification since 1987 with two different desertified stages. First stage from 1987 to 2000 is a serious sandy desertification period, characterized by the fixed sand dunes decreasing at a high speed, and the semi-fixed and active sand dunes increasing remarkably. The second stage spanned from 2000 to 2006 and the sandy desertification was weakened greatly. Although a large area of fixed sand dunes transformed to other types, it is still the dominant type in the Ointdag region at 2006. Spatial change detection based on active sand dunes showed that the area of expansion is much larger than that of reversion in the past two decades, and that several active sand belts have been formed. It suggests that sandy desertification controlling of the Otindag Sandy Land will be a long-time task.