Present status and cause of land desertification in the Yarlung Zangbo River basin

The Yarlung Zangbo River basin is a spacial zone in the south of Xizang, the types, distribution and causes of desertified lands have special features. The type, area, distribution and damage of desertification land in the Yarlung Zangbo River basin are firstly analysed in detail by using latest investigation information. According to the classification criteria of desertified land types and grades, the desertified land in the Yarlung Zangbo River basin can be divided into three grades and five types: fixed sand (dune) land, semi bare sand and gravel land, semi fixed sand (dune) land, base sand and gravel land, and shifting sand (dune) land. The desertified lands in the basin are mainly distributed in the wide valley floor and tributary junction area. The main factors affecting desertification are fragile eco environment, climate warming and drying and over exploitation of land resources. The man made factors leading to desertification in the Yarlung Zangbo River basin are over cutting and over grazing, dominated by over grazing.