Ecological Vulnerability Assessment And Its Uncertainty Analysis

At present,China’s ecological environmental problems are becoming increasingly serious,which leads to the decline of ecosystem stability and the increase of ecological vulnerability.Ecological vulnerability assessment can provide important guidance for regional ecological sustainable development and is of great significance.On the other hand,the existing ecological vulnerability assessment pays little attention to the uncertainty of results,and fails to fully identify the sensitivity characteristics of the assessment results,which affects the reliability of the results.This study is to analyze the overall spatial distribution characteristics of the ecological vulnerability of Dalian city and to identify the sensitivity characteristics of evaluation index system.We constructed an urban ecological vulnerability index system based on sensitivityrecovery-pressure model(SRP)and a total of 19 indexes were selected for evaluation covering climate,topography,surface,disaster,function,vitality,structure,population and economic pressures.ArcGIS and other software were used to image and standardize each index data.The weight of each index was calculated by expert scoring method and analytic hierarchy process,and the ecological vulnerability index was calculated by weighted superposition method.The ecological evaluation results were categorized into five levels according to the degree of vulnerability.Then we introduced one-at-a-time method(OAT)to estimate the sensitivity of results to the variation of index weights by constructing three indicators--mean of the absolute change rate,pixel change rate and the proportion of uncertain area.The conclusions for this work could be drawn as follows:(1)The average ecological vulnerability index value of Dalian city is 0.411 and the area proportion of slight vulnerability,light vulnerability,moderate vulnerability,high vulnerability and extreme vulnerability is 8.16%,23.69%,41.00%,22.97% and 4.17% respectively.Among all the districts,the ecological vulnerability of Xigang District is strongest,and the ecological vulnerability of Zhuanghe city is weakest.(2)The areas with highest vulnerability lie in city center and the east area of Ganjingzi District,while areas with lowest vulnerability lie in the northern part of Dalian and the junction of Ganjingzi District and Lushun District,and distribution of areas of other vulnerable levels is more dispersed.The main distribution patterns are: areas with low ecological vulnerability has high vegetation coverage and small population economic pressure,while areas with high ecological vulnerability has large human activities.(3)The weight change has a certain impact on the vulnerability evaluation results and the calculation results of different weight values have certain spatial differences.The soil organic carbon has the greatest impact on the evaluation results.The calculated maximum mean of the absolute change rate and maximum pixel change rate are 11.49% and 17.27%,respectively,and the maximum proportion of uncertain area is 22.84%.The weight of soil organic carbon should be carefully considered to reduce the uncertainty of evaluation results.