Land Degradation Assessment In Tibetan Plateau, China: A GIS & RS Approach

This study examines the use of Geographic Information System GIS and Remote Sensing RS in mapping Land Use/Cover in Tibetan Plateau (TP) of China between 1994 and 2001 so as to detect the changes that have taken place in this status between these periods.On the grounds of geography, ecology, agriculture and spatial analysis, based on plenty of data collected from field observation, remote sensing RS, geographic information system GIS and global position system GPS technique were used to construct the land cover database and do the analysis of the grassland degradation.The study area (one of the source regions of Yellow River) is generally defined as the riverhead area in Qinghai province. As the birthplace and 'water tower' of the great watercourse, the region plays a vital role in regulating the water volume in the Yellow River. Changes in the stream discharges of the Yellow River source region directly affect the water resources of the middle and lower reaches of the river. In recent years, due to climate change, the glaciers, permafrost, lakes and wetlands, overgrazing, and the hydrological and ecological environments in this region have undergone dramatic changes that have far-reaching implications for the economic and social conditions of people's lives not only in the source region itself, but also in the middle and low reaches of the Yellow River.Climate change and human activities are the driving forces of the ecological and environmental degradation of study area.The research area is a typical alpine grazing area. The grassland used for grazing accounts for 80% and forestry about 19% of the total research area, the degraded grassland area accounts for 26-46% of its total. The distribution of alpine meadow is controlled by landform, climate and human activities, especially sever degraded alpine meadow.During the last 50 years, statistics show that there is an apparent trend of warming and decreased precipitation in the study area. The regional climate is becoming warmer and drier. This change leads to a series of ecological and environmental problems, suchas glacier retreat, permafrost thawing, wetland and marshland drainage, lake shrinkage and soil deterioration. The combined effect of rising temperature, permafrost degradation, overgrazing and rodent plague has led to severe ecological deterioration. Grassland coverage has degraded alarmingly; 'Soil erosion' and desertification have increased at a devastating rate. In the 1990s as the temperature rose, the major tributaries in the Yellow River source region frequently suffered dry periods, which led to a drop in water resources in the region and across the entire Yellow River basin. From the changes in the glaciers, permafrost and the pattern of land coverage, we can conclude that climate change is the major factor leading to the overall ecological degradation in this region while localized human activities, like industry, agriculture and overgrazing have aggravated the situation. Meanwhile the river itself is under threat from this deterioration in its birthplace.Under climate change and the human activities, the plight of the Yellow River and its source region is a clear and urgent warning to the world that global warming is harming us now and is going to get worse. To tackle climate change and especially to mitigate the part human activity played in causing climate change is not a task for the people of Yellow River source region alone. It requires the concerted effort of China and all other countries in the world to act now.