Land use ecological risk evaluation in Three Gorges Reservoir area based on normal cloud model

Abstract: Some basic data couldn't be accurately acquired or quantitative evaluated in evaluation of land use ecological risk, so there are the fuzziness and uncertainty problems in the evaluation index and results. In order to solve this problem effectively, normal cloud model comprehensive evaluation model was introduced. In Normal cloud evaluation model, the status of each evaluation index can be intuitive found out and the influences of each evaluation index on land use ecological risk in Three Gorges Reservoir area can be objective reflect. With the LandSAT TM remote sensing data, social and economic data, environmental monitoring data of Three Gorges Reservoir area in the year of 2000 and 2012, the evaluating indexes system was built to evaluate the land use ecological risk in Three Gorges Reservoir area based on the PSR (pressure-state-response, PSR) model. In model, the ecological risk pressure indexes included the proportion of agricultural land, construction land scale, the industrial pollutants emission intensity, the strength of farmland non-point source pollution, road network density and population density; the state of ecological indexes included patch density, shape index, circumference surface integral dimension, concentration, average nearest neighbor distance; the risk response indexes included composite structure index, vegetation coverage, diversity index, the coordination degree of water and soil, land degradation rate. The evaluation standards were set up by referring to a large number of data and consulting relevant experts. Study results indicated that: 1) The level of average land use ecological risk belonged to the lower risk totally in Three Gorges Reservoir area. At the same time, the level of land use ecological risk had an increasing trend. The average normal cloud membership degrees of lower risk were the max in all risk levels both in 2000 and 2012. But the value decreased from 0.4233 to 0.4013 from 2000 to 2012 in Three Gorges Reservoir area. And the second risk level was medium risk. The value was 0.3955, near the value of lower risk tightly in 2012 year. 2) The land use ecological risk level had an increasing trend from northeast to southwest in Three Gorges Reservoir area. There were one county in low risk level, ten in lower risk level, six in medium risk level, and one in highest risk level in 2000. The number of counties in higher risk level and highest risk level increased obviously from 2000 to 2012. Three counties were added into higher risk level, and one added into highest risk level. Those counties distribute in southwest of Three Gorges Reservoir area. Changshou district, which land use ecological risk level increasing from lowest to highest rapidly, needed to be paid most attention especially. 3) The distribution and change of land use ecological risk level were different obviously in each part of Three Gorges Reservoir area. The head area of Three Gorges Reservoir area, including four counties in the Hubei province, belong lowest risk or lower risk area. And the change of risk level was weak. In the hinterland area of Three Gorges Reservoir area, the levels of land use ecological risk were not highest. But the change of risk level was obvious. In four counties, including Puling, Fengdu, Shizhu and Wanzhou, the risk levels increased. Only in Yunyang, the risk level of decreased. In the end area of Three Gorges Reservoir area, the level of use ecological risk was highest for most pollution. Appling normal cloud model, the uncertainty mapping of each evaluation index was realized, and the results had more objectivity through considering to randomness and fuzziness in the processes of evaluation index quantization and level division. The results offer references for land reasonable using and ecological protection policy making in Three Gorges Reservoir Area.