IMPACT OF LAND USE AND LAND COVER CHANGE ON ENVIRONMENTAL DEGRADATION IN LAKE QINGHAI WATERSHED, NORTHEAST QINGHAI-TIBET PLATEAU

Lake Qinghai, the largest saline lake in China, covers 4234 km(2) (2007) with a catchment area of 29 660 km(2) on the northeastern margin of the Qinghai-Tibet Plateau. The ecosystem of the lake is extremely vulnerable and sensitive to global climate change and human interference. However, little information is available on land use/cover change (LUCC) in Lake Qinghai watershed. Using a geographical information system (GIS) and remote sensing (RS), this study analysed land use and land cover change pattern in Lake Qinghai watershed between 1977 and 2004 and discussed major environmental issues in this area. LUCC analysis indicated that grassland (63 per cent) and water body (18 per cent) dominated in the watershed and the magnitude of the land use and land cover change was generally low; the percentage of the change of various land types relative to the total area was less than I per cent. From 1977 to 2004, cropland, sandy land, bare rock, salinized land, swampland and built-up areas increased by 0.43, 0.35, 0.24, 0.06, 0.03 and 0.03 per cent of the total area, respectively; in contrast, water body, grassland and woodland decreased by 0.99, 0.22 and 0.05 per cent, respectively. Moreover, the area of LUCC tended to expand from places around the lake to the upper reaches of the watershed during the last three decades. The LUCC transition pattern was: woodland converted to grassland, grassland converted to cropland and water body converted to sandy land. Lake level decline and grassland degradation are major ecological and environmental problems in Lake Qinghai watershed. The level and area of the lake decreased at the rate of 6.7 cm a(-1) and 6.4 km(2) a(-1), respectively, between 1959 and 2007, resulting in sandy land expansion and water quality deterioration. Lake level decline and area shrinkage was mainly attributed to climate change, but grassland degradation was mainly resulted from anthropogenic activities (increasing population, overgrazing and policy). Copyright (C) 2008 John Wiley & Sons, Ltd.