The Urban Ecological Risk Assessment Based On GIS

Urban ecological risk assessment is a part of the regional ecological risk assessment.With the deepening of the theory and methods of the regional ecological risk assessment, urban ecological risk assessment become an important part of the regional ecological risk assessment. And compared to the traditional ecological risk assessment, urban ecological risk assessment has multiple ecological risk sources, multiple ecological risk receptors, multiple ecological risk effects, emphasizing the uncertainties and spatial heterogeneity and so on. Constructed urban ecological risk based on multiple ecological risk sources, multiple ecological risk receptors , multiple ecological risk effects of the Shanghai urban ecological risk assessment system, using remote sensing data, statistics and experimental survey data, the use of fuzzy comprehensive evaluation method, evaluation of the Shanghai Urban ecological risk. The results for the Government to strengthen the urban ecological planning and ecosystem management has an important value. The main conclusions are:1. From the perspective of the urban ecological risk's classification, lack of high level ecological risk.The distribution of the very low ecological risk is small. High-level ecological risk and low-level ecological risk distribution is relatively small.2. From the perspective of the urban ecological risk spatial pattern, the city central area is the high ecological risk, and the suburban ecological risk is low; Shanghai to the level of ecological risk-based, including the formation of a number of urban centers, including areas of high ecological risk level , was the "island" like being surrounded in the area of middle ecological risk levels.3. From the perspective of the citys distribution, ecological risk, high-level ecological risk mainly distribute at Baoshan District, along the Yangtze River estuary area, the central part of Pudong, Songjiang and so on, and the area is 487.05km2. The middle area of the ecological risk level is 6211.63 km2. Low-level ecological risk is mainly in the central part of Chongming Island, and the area is 68.97 km2. Very low level of ecological risk is mainly in the central part of Chongming Island, and the area is 13.78 km2.4. From the perspective of spatial analysis, the mean of the ecological risk index can reflect the different average buffer size of the overall level of ecological risk. The mean of urban ecological risk in Shanghai in 2007,from the city center descending to the suburbs, in the 42km buffer range, the district is mainly farmland, farmland play a positive effect on the ecological environment,also an important component of the ecosystem, so the area of ecological risk index is low. The mean of urban ecological risk in Shanghai achieve the minimum ecological risk after he showed a slowly rising trend. The standard deviation of ecological risk index can reflect the different ecological risks within the buffer level of the internal differences. The standard deviation of change in ecological risk index range of large, the state of ecological risk index for the lowest standard deviation of the buffer appears in the 6km range, the city construction land-based, the ecological risk assessment in the area of high value, so the standard deviation of ecological risk index lowest in the area. The peak in 34km buffer range, the region is in the Pudong New Area, Minhang District, and so on, land-use type complex, with each turning point of ecological risk assessment have emerged in the area, making the regions ecological risk index for the standard deviation of the spatial distribution pattern is more complex than the central city.