Ecosystem Health Assessment Of The Nanliu River Basin

With the rapid and continuous development of Chinese population, an ever increasing social economy, a large-scale exploitation and utilization of natural resources, exceed the ecological capacity. The global and regional ecological environment changes dramatically in consequence. A series of the ecological environmental problems, such as the global warming, water pollution, heavy metal pollution, loss of biodiversity, have become obstacles to the sustainable development of human society. Therefore, protecting and restoring ecological environmental health has become a hot issue of research.By using pressure- state- response(PSR) model and relative evaluation method, selecting 14 related indexes, including population density, interference index of population, land reclamation rate, vegetation coverage, diversity index, ecological elasticity index, the net primary productivity of vegetation, forest coverage, etc, the assessment of ecosystem health is studied. Specifically, taking advantage of RS and GIS, single and integrated factors assessment of ecosystem health and its causes are given in 78 town-level units in Nanliu river basin. Conclusions are as follows:(1) For single-factor evaluation, the interference index of population in first level is mainly distributes in Liu Wan mountain areas, human interference is weak; Hepu, Yuzhou and Beiliu counties distribute the most intense human interference for five levels. Ecological elastic index in coastal areas, Yuzhou and nearby towns was poor,generally in the level 4 and below, ecological recovery ability is poor. Among them, Dangjiang is the only unit in fifth level. For the sensitivity of soil erosion, Hepu and Yuzhou counties is low, generally locates on level 3 or above. Among them, due to spatial variation of terrain slope, the Yunkai and the LiuWan mountainous terrains are the most susceptible to erosion.(2) For comprehensive factors evaluation, Yuzhou County in the upstream and coastal ecosystems in downstream pressure conditions are bad by pressure factors evaluation, however, couties in midstream are better. Comprehensive health state indicators in the overall showed space decentralized, local gathered. More specifically, Yuzhou and Hepu counties scattered than Bobai County. Comprehensive response indicators of ecosystem response to conditions on the spatial distribution are more dispersed, less agglomeration effects.(3) Comprehensive ecosystem health state in midstream and downstream are better than upstream and costal units, that is to say, Bobai County, Lingshan County, north units of Hepu County, are better than Yulin and Hepu counties. There is spatial similarity of ecosystem health states between Hepu and Yulin counties, but the causes are different. There are 18 first level towns, accounting for 23.1% of the overall towns, mainly distribute in the southern of Bobai County, Pubei County, Lingshan County and southern districts of Yulin County; 28 towns in secondary level, accounting for 35.9%, mainly distribute in the south areas of Yulin County, most areas of Bobai County, northern areas of Hepu County and some units of Pubei County; 19 towns in third level, accounting for 24.4%, mainly distribute in the areas north of the state of Yulin County, Luchuan and Pubei counties; 10 towns in forth level, accounting for 12.8%, mainly distribute in the centre of Yulin County and south of Hepu County; 3 towns, accounting for 3.8% of the total, concluding Beiliu, Shagang and Dangjiang towns in fifth level.(4) According to the ecosystem assessment, the results show that the main condition of ecosystem health are closely related with the local topography, socio-economic structure and development, environmental protecting investment, land use patterns and so on. Therefore, raising awareness of environmental protection, developing of eco-protection measures, regulating human social activities are all of critical importance.