Spatial Pattern Of Ecological Security Assessment And Simulation In Coastal City Based On Remote Sensing And GIS

Ecological security is the basis for human survival and development.In recent years,China's urbanization has accelerated and its economy has developed rapidly,especially in coastal cities.The acceleration of urbanization and economic development have also resulted in the continuous changes of land use patterns and drastic changes in urban ecological security.The huge changes in the coastal ecological environment have led to the more vulnerable ecological environment in the coastal areas,and the ecological security in cities is the basis of sustainable development.Therefore,it is urgently needed to conduct a more in-depth study on ecological security in coastal cities.Ningbo located in the southeast coast of China is a typical representative of many coastal cities.The rapid population and economic growth led to the continuous expansion of the surface buildings and the continuous reduction of the surface vegetation cover,all of which affected the ecosystem of Ningbo.In addition,other factors such as reclamation,industrialization,emissions and waste water discharge put pressure on the ecological safety in Ningbo.In order to ensure the sustainable development of Ningbo,it is urgent to study the space-time pattern of ecological security.Based on theoretical analysis,this paper uses expert evaluation and principal component analysis as research methods to evaluate the ecological security of Ningbo City from 1975 to 2015.We studied the spatial driving factors that affect the change of ecological security,and predicted the ecological security patterns in Ningbo in next 30 year.All of these are to help local governments to optimize urban planning,implement strict land use management,improve the ecological environment,and provide a basis for building an environment-friendly city.The main contents of this paper are as follows:(1)Evaluation of ecological security pattern and its relationship with spatial driving factors.We used the expert evaluation method to evaluate the ecological security scores of sampling points,and analyzed the spatial disparity pattern and time variation of ecological security based on remote sensing,GIS,and spatial driving factors.The key spatial driving factors for extracting ecological security based on remote sensing image and vector dataset include distance to the city center,distance to the districts center,distance to the main roads,distance to the main pollution source,the mean NDBI,and the mean NDVI.Using generalized additive models to analyze the relationship between ecological security pattern and spatial driving factors.The results show that the ecological security situation of Ningbo has been deteriorating since 1975,and that the center of Ningbo and Cixi are in very insecure.The main factors affecting ecological security are the distance to the city center,the distance to the districts center and the distance to the main roads,and the mean NDBI.Among them,the impact of the average NDBI is the largest spatial driving factor.(2)Selecting the optimal spatial driving factors for principal component analysis to obtain ecological security pattern.The GAM analysis was used to select the optimal spatial driving factors that affect the ecological security of Ningbo.Using principal component analysis to extract the main components of the optimal spatial driving factors in each year.Based on the extracted principal component data and GIS spatial analysis,the spatial pattern of ecological security patterns were obtained,and the dynamic change process of ecological security was analyzed.The results show that the most important spatial driving factors affecting ecological security are the average population density,distance to the districts,the mean NDVI,the mean NDBI,and distance to the city center.The results of the ecological security patterns of principal component analysis also show that the ecological security has been deteriorating.(3)Prediction of future ecological security patterns based on Cellular Automata.The optimal spatial driving factors that the averaged population density,distance to the districts,the mean NDVI,the mean NDBI,and distance to city center were taken as the driving factors.The cellular automata model was used to simulate the future ecological security patterns from 2020 to 2050.The simulation results that the ecology of Ningbo will continue to deteriorate in the future,but the rate of deterioration will gradually decrease.The ecology of the center of Ningbo,Cixi,Yuyao,Fenghua,Jiangbei,Zhenhai,Beilun,Ninghai and Xiangshan are still at a very insecurity.However,the ecological security of the suburbs is in good condition.(4)Analysis of the future pattern of ecological security taking into account the effects of storm surge flooding.The Arc GIS spatial analysis was used to obtain the submerged area of Ningbo where the water level rose by 1 to 10 meters,under the influence of storm surge,based on the DEM data.According to the rising level of different water levels,the submergence period of the submerged area is divided into 2 to 20 hours.Different submerged areas are divided into different ecological security level.Integrate the ecological security pattern of the inundated area with the CA-simulated ecological security pattern,and obtain the future ecological security pattern that takes into account the impact of storm surge inundation.The simulation results indicate that the center of Ningbo,Cixi,Yuyao,Zhenhai,and Beilun are very insecure and have a relatively large range,from 2020 to 2050.The ecology in the northern part of Yuyao,the north of Cixi,and the northeastern region near the coastline are very insecure.