Study On Ecological Security Evaluation And Ecological Security Pattern Construction Of Pingtan Island Based On Remote Sensing

With the continuous advancement of urbanization,the rapid growth of urban population and construction land is obvious to all.The resulting ecological security problem has become a great challenge to urban sustainable development.As a coastal outpost city in the Economic Zone on the West Bank of the Strait and an economic demonstration area for Taiwan,Pingtan is an island with independent natural and geographical characteristics.Since the large-scale development in 2009,its ecological environment has changed strongly.The ecological security of Pingtan is particularly important,which is related to the ecological evolution of the island,trade exchanges,economic and trade cooperation and quality of life of residents on both sides of the Taiwan Strait,Therefore,Pingtan ecological security has strategic significance to maintain the security and stability of national coastal areas.Taking Pingtan Island as the study area,based on remote sensing image data in 1984,1996,2008 and 2020,basic geographic information data,DEM data and soil data,Pingtan land cover classification is carried out.According to the ecological and environmental problems faced by Pingtan,constructs a comprehensive ecological security evaluation system,evaluate the evolution characteristics of Pingtan ecological security in recent 40 years.On this basis,build the ecological security pattern of Pingtan in 2020.The main results are as follows:(1)Pingtan land use/cover change in recent 40 years:Pingtan land cover classification is carried out based on the random forest classification method based on feature optimization.The results show that from 1984 to 2020,Pingtan forest land area increased by 22.75km~2,the proportion in the total area of Pingtan increased by 8.04%.Construction land area increased by 70.3 km~2,the proportion increased by 24.84%.Cultivated land decreased by 68.1 km~2,the proportion decreased by 24.06%.Water area decreased by 23.8 km~2,the proportion decreased by 8.41%.The increased construction land mainly comes from the conversion of cultivated land and water body,It is mainly distributed in the central urban area of Pingtan County and the southwest.From 2008 to2020,the land cover change in Pingtan was particularly drastic,in which the reduction of cultivated land was 15.0 km~2more than the total from 1984 to 2008,and the growth of construction land was 28.98 km~2more than the total from 1984 to 2008.(2)Temporal and spatial changes of Pingtan ecological security in recent 40 years:Based on the ecological security factors of wind and sand fixation,geological disasters,ecological protection and landscape ecological security,a comprehensive ecological security evaluation index is constructed.The ecological security status of Pingtan is divided into five levels:risk level,sensitive level,critical security level,relative security level and security level.From 1984 to 2020,the overall ecological security of Pingtan was at a relatively safe level and had obvious spatial aggregation.The overall situation of ecological security showed a trend of first improving and then deteriorating.From 2008to 2020,the ecological security level of mountainous areas in the northeast of Pingtan(Zhonglou township and Liushui town)and the South(Beicuo town)changed from relative security level to critical security level.Most of the land with ecological security level of security level in the island changed to ecological relative security level.The ecological security level showed an obvious downward trend,and its spatial structure tended to be discrete.From 1984 to 1996,the overall level of ecological security in Pingtan improved,and the ecological security in areas over 100 km~2remained relatively stable.From 1996 to 2008 and from 2008 to 2020,the area with negative ecological maintenance rate increased significantly compared with the first period,and the level of Pingtan ecological security decreased,and the level of Pingtan ecological security decreased most sharply in the third period.From 1984 to 2020,the area of land with stable ecological maintenance in Pingtan decreased significantly.In addition,the total land area with positive ecological maintenance rate in the three periods shows a trend of decreasing first and then increasing.The area with very high,very high and high ecological maintenance level accounts for a relatively low proportion,while the area with high ecological maintenance level accounts for a relatively high proportion.(3)Analysis on the characteristics of Pingtan ecological security pattern:Based on MSPA and landscape connectivity evaluation and minimum cumulative resistance model,identify ecological sources and ecological corridors,build the evaluation index system of ecosystem service function importance and ecological sensitivity respectively,extract the key areas of ecological protection according to the evaluation results,and build the ecological security pattern of Pingtan in 2020.The constructed ecological security pattern consists of Pingtan ecological protection key areas,12 ecological source patches,13ecological corridors,9 ecological nodes and 15 ecological obstacles.Among them,the total area of ecological source is 34.14 km~2,accounting for 12.06%of the total area of Pingtan Island,the area of key ecological protection areas is 92.38 km~2,and the total length of corridor is 88.38 km.On this basis,combined with the ecological security evaluation results,the corresponding suggestions on land use development and ecological environment protection are put forward.