Temporal And Spatial Evolution And Risk Assessment Of Desertification In Haixi Mongolian And Tibetan Autonomous Prefecture

For a long time, desertification has been a common concern of researchers governmental agencies as an environmental problem, which directly affects the survival and development of human beings. Haixi, located in the arid and semi arid and alpine area of Northwest China, was one of the most serious desertification areas in Qinghai and even the whole country. At present, the research on the desertification in Haixi was mainly focused on the Qaidam Basin. The thesis extends the research scope to the whole prefecture for the first time and makes a comprehensive study on the process of desertification.The thesis analyzes the spatial-temporal evolution of desertification in the past 40 years by remote sensing interpretation and the risk of desertification in different RCPs and in different periods of the future, based on the Landsat remote sensing image data and using NDVI as the index to evaluate the change of desertification. The thesis also analyzes the influence of natural and human driving forces on the desertification in the study area, and puts forward the corresponding countermeasures and suggestions for the desertification control. Main research achievements are as follows:(1) The temporal-spatial evolution of desertification in the past 40 years. In the regional distribution, the degree of desertification was from heavy and light from the Qaidam basin to the outside; in time scale, the area of desertification land experienced the change process of increasing first and decreasing later, which was the biggest and the most serious in 1995 with the glowing period from 1975 to 1995 and the reversal period from 1995 to 2014. The geographic coordinates of the center of gravity of the desertification and the different degrees of desertification all experienced the migration process of first to the east then to the west, and the mobility scale of the gravity center of the lesser degree desertification is less than the heavier degree.(2) Driving force of desertification. The inter-annual variations of climate, precipitation and wind showed the warm-humid tendency of climate. Because the warm-humid climate is conducive to desertification reversion, the expansion of desertification was conducive to the result of warm-humid climate affecting desertification in 1975~1995, and consistent in 1995~2014. On the one hand, the human activities have a huge influence, even more than the climate in arid and semi-arid areas with fragile ecology; on the other hand, the human factors could be controlled that the gradual rationalization and standardization of human activities and the enhancement of ecological environment protection result in the desertification reversion in the help of the warm-humid tendency of climate.(3) The risk assessment of desertification. In the geographical distribution, the risk of desertification will be from heavy to light from Qaidam basin to outlying mountainous area in the future, similar to the geographical distribution of desertification land, in which the high risk land will occupy the highest proportion of the risk area. From different climate change scenarios, the risk of desertification will be highest under the scenario RCP4.5 and lowest under RCP2.6 and RCP6.0.(4) Countermeasures of desertification control. Early desertification control resulted in little in the study area. Since the 1990 s of the last century, desertification control had been strengthened and the expansion of desertification has been curbed with the introduction of series of environmental protection policies, however, many problems still arose in the governance process. The thesis puts forward three new proposals for these problems and the desertification control based on good environment governance. As a new concept of environmental control, good environmental governance can be applied to the desertification control, which is conducive to the mutual cooperation and complement each other among local government, industrial and mining enterprises and civil society, form a sound environmental management system and promote the sustainable development.