Left River Basin Land Use / Cover Change And Ecological Security Assessment

Varying in land use/coverage in the last several decades has aroused a series of ecological and environmental problems, which have put a direct threat to region's social and economic sustainable development and ecological safety. Although researches on this problem have obtained certain achievements, it is still far from demands. Zuojiang river basin is a typical region of ecological and environmental fragility. With the increase of population, the overuse of land in this basin is disturbing the environment severely, and the vulnerability of its ecology system is even converting into environmental disasters, which in turn influenced the continuous utilization of natural resources and the basin's sustainable development.Taking Zuojiang river basin as research area, TM satellite images of 1996 and 2005 as data sources, this essay studied the land use/coverage change process of this basin in the past 9 years and its driving mechanism by using RS-GIS-GPS integration technology; made a semi-variant function analysis and spatial interpolation of this basin's ecological vulnerability to make this basin's ecological vulnerability quantitative and local by using ecology vulnerability model; made an qualitative and quantitative analysis of Zuojiang river basin's ecology safety by adopting comprehensive evaluation mode. The research results included: (1) The main land use/coverage change in Zuojiang river basin can be described as"four increases and one decrease", by which"four increase"refers to the areas of farm land, forest land, construction land and water areas is increasing, while"one decrease"means the percentage of unutilized land area in total land area is decreasing. Analysis of driving forces showed that economy factors, such as GDP, fixed assets investment of the whole society, gross industrial output value are the most important factors in affecting farm land change. (2) Semi-variant function analysis conveyed that region's ecological vulnerability index is strongly correlated, and the correlation distance is about 47km, which is at the level of crossing county or town administration cell. This presented that there is large local similarity in ecological vulnerability of nearby counties or towns. The peak and low area,valley plains and platforms in the northwest and central part of this basin have high ecological vulnerability, while that of the hilly lands in the southeast is low. The ecological vulnerability of Zuojiang river basin is both the results of natural and human forces. (3) The safety type of agricultural ecology-economy system in Zuojiang river basin is mainly"relatively secure"or "semi-secure". Therefore, some corresponding countermeasures were suggested to improve the healthy level of ecology-economy system in Zuojiang river basin, which is aimed to make this basin develop sustainably.