Ecological Health Evaluation On Zhejiang Coastal Wetland Based On Landscape Pattern Change

Coastal wetland is rich in biodiversity and can provide a variety of ecosystem services for people.Coastal wetland is sensitive to environmental changes and has become a relatively fragile ecosystem.Zhejiang coastal wetland is located in strategic position of East Asian-Australasian Flyway and plays an irreplaceable role in maintaining global biodiversity.Besides,Zhejiang coastal wetland plays a significant role in maintaining ecological security of coastal areas.Zhejiang coastal area is one of the most developed areas in China,but rapid urbanization and frequent human activities has resulted in great pressure.Now coastal wetland is facing the environmental problems such as degradation of wetland and declining of biodiversity.For effective management of wetland and sustainable development,the ecological health status and evolution trend of coastal wetlands were evaluated and the driving factors were analyzed.In this study,we took Zhejiang coastal wetland as the research object and extracted the information of remote sensing data by using geographic information system(GIS)and remote sensing(RS).Then we can obtain the spatial distribution of Zhejiang coastal wetland by applying decision tree classification.Combined with relative statistical data,we studied the change of landscape pattern of coastal wetland and comprehensively evaluated the evolution trend of coastal wetland ecological health based on some theories and methods,such as Markov shift model,landscape index.Under the guidance of pressure-state-response(PSR)model,we took bay for the evaluation unit,using combination weighting of Analytic Hierarchy Process(AHP)and entropy method to determine the weight of each index.Then we used comprehensive evaluation method to evaluate the spatiotemporal variation of Zhejiang coastal wetland ecological health.The main findings are as follows:From 1990 to 2017,the area of coastal wetland decreased rapidly,but the area of marsh wetland increased gradually.The area of coastal wetland in Zhejiang decreased by 607.17km~2,a reduction of 21.76%.natural wetland decreased by 1059.26km~2,artificial water increased by452.09km~2.Among natural wetland,marsh wetland increased by 221.26km~2.During1990-2017,human activities have aggravated the intensity of fragments in class scale,especially artificial water and marsh wetland.Besides,the extent of fragments in landscape scale has intensified.The value of Shannon diversity index approached 1.6 and showed the fluctuating trend.It showed that the landscape diversity was high in the study area.Density of population,per capita GDP and seawater aquatic production had close relationship with wetland landscape change.From 2008 to 2017,the degradation trend of Zhejiang coastal wetland has been controlled gradually,and the health status of some bays began to show the improved phenomenon.The ecological health status varies from bay to bay.From 2000 to 2017,the ecological health status in Hangzhou Bay,Xiangshan harbor and Yueqing bay all decreased firstly and increased subsequently.However,Sanmen bay and Taizhou bay increased firstly and decreased subsequently,and Wenzhou bay gradually decreased during the period.Overall,the health status of Taizhou bay and Wenzhou bay deteriorated seriously.However,to some extent,the health status of Hangzhou bay,Yueqing bay and Xiangshan harbor gained some recovery because of a series of protecting measures.Population density,anthropogenic disturbance,intensity of mariculture and reclamation were the major driving factors for the deterioration of coastal wetland ecological health.Among them,population density and anthropogenic disturbance were the main limiting factors,and intensity of mariculture and reclamation were the main influencing factors.Meanwhile,nature reserve establishment played significant roles in maintaining and recovering coastal wetland ecosystem.