LAND USE CHANGE AND ITS IMPACT ON THE ECO-ENVIRONMENT IN THE SOURCE REGION OF THE YANGTZE RIVER DURING THE PAST 15 YEARS

Based on 1986 TM and 2000 ETM data,the land use and landscape pattern change in the source region of the Yangtze River was studied with geographical information system (GIS) and the analytic method of landscape ecological spatial patterns in both spatial and temporal aspects in this paper. Conclusions of this study are drawn as follows:from 1985 to 2000,woodland area reduced by 54.2%,wetland area by 42.69%,while the construction land,cultivated land area and unused land area increased by 120%, 43.83% and 21.1% respectively. The area order of individual land use changes was grasslandunused landwetlandwater body forestland cultivated land construction land. As a whole, the swap change was greater than its quantity. The analysis of the landscape pattern shows that the landscape fragmentation degree,the fractal degree and the diversity index increased,implying the enhancement of landscape heterogeneity. The eco-environment in the study area is very vulnerable to the land use change,resulting in land desertification and loss of water and soil. These changes result in the degradation of high-cold meadow vegetation and wetland. Abnormal climate and irrational human activities were the major reason of these changes.