Assessment Of Ecological Vulnerability In Estuarine Island

Estuary islands are usually rich in biological resources,land resources and available energy,thus are crucial natural ecosystem.However,with the climate change,global sea level are rising,the estuarine wetland hydrological processes are changing,and estuarine islands may experience risks such as passive climax submergence,beach soil erosion,biological invasion,and saltwater intrusion.Therefore,the assessment of ecological vulnerability of estuary islands needs to be resolved.This paper constructed the evaluation system for the vulnerability of estuarine islands ecosystem under the background of climate change and the impact of human activities.Also,taking Chongming Island,the typical estuary island,as an example,mainly based on measured data,remote sensed data and meteorological data,we evaluated the ecosystem vulnerability of Chongming estuarine island,and explored the spatial-temporal differences and the key influencing factors of ecological vulnerability of Shanghai Chongming Island,for the contribution to the sustainable development of different regions in Chongming Island.The main results of the study are as follows:(1)An assessment system for ecological vulnerability of estuarine islands was established:based on the pressure-state-response assessment framework,we selected four indicators at the pressure level:land use intensity,flood disaster intensity,storm surge intensity,and saltwater intrusion intensity;seven indicators at state level:soil salinity intensity,NDVI,EVI,landscape fragmentation,and biodiversity indicators,soil organic matter and net primary productivity(NPP);two indicators in the response layer:ecological protection grades and dam protection capabilities.Through spatial principal component analysis,the weights among the indicators were determined,and finally an ecological vulnerability assessment framework for estuarine islands was constructed.The evaluation system could well evaluate the ecological vulnerability of estuary islands.(2)Assessment of each indicators of the ecological vulnerability of Chongming Island:The press indicator was higher in the area along the north of Chongming Island and Dongtan area,and influenced mainly by saltwater intrusion and flood water logging,and higher in 2015 than in 2005.The state indicator was higher in the central part and the area along the north of Chongming Island,maily influenced by the vegetation growth condition and ecodiverstiy.The spatial trends in 2005 and 2015 were basically the same,but it showed the overall decline in 2015.The response indicator was higher in southern and central area of Chongming Island,lower in the area along the north and Dongtan area,mainly influenced by protection grade of the dam,the high ecological protection and NPP,and higher in 2015 than in 2005.(3)Overall assessment of the ecological vulnerability of Chongming Island:This study obtained the spatial and temporal pattern of ecological vulnerability of Chongming Island in 2005 and 2015.The ecological vulnerability of Chongming Island changed from 0.39 in 2005 to 0.36 in 2015.From 2005 to 2015,the original lower ecological vulnerability(<0.2)and higher regions(>0.6)were transformed into medium-level ecological fragility(0.2?0.6).Some of forest lands were converted into agricultural land and construction land,while in the northern area,due to sediment accumulation,the areas that were directly inundated with seawater were converted into wetlands even forest land.Spatially,Chongming Dongtan and Qilong Town(Jiangsu)had the highest ecological vulnerability due to the effects of saltwater intrusion and flooding;Xincun Township and Shangshi Agricultural Park followed with relatively higher ecological vulnerability,while the remaining regions had lower ecological vulnerability.This study also guided the development of protective measures in various regions of Chongming Island,such as strengthening the construction of dams in areas with high vulnerability,using physical methods to control the intrusion of salt water,and the need to plant salt-tolerant alkaline plants to gradually build stability and so on.In this study,an empirical study of the comprehensive assessment of the ecological vulnerability of Chongming Island was conducted at the regional scale,which is of significance for the establishment of a theoretical framework for ecological fragility of estuarine islands.