Analysis Of Wetland Landscape Dynamics And Driving Factors In The Yalu River Estuary: A Transboundary Comparison Between China And North Korea

The ecological environment of estuary wetland is both fragile and important,which is a sensitive area of climate change and a focus area of current wetland research.With the rapid development of global climate change,economic integration and urbanization,the impacts of climate change and human activities on the spatial and temporal dynamic evolution of estuary wetland are revealed,and the main driving factors and interference degrees of wetlands are qualitatively and quantitatively analyzed,which are the prerequisite and foundation for the conservation and management of estuary wetland resources,and are the scientific basis for ensuring the security of estuary wetland ecosystem and the sustainable utilization of wetland resources.Yalu River estuary is located in the northernmost part of the Chinese coastal zone.It is one of the important coastal wetland in China.It is also an important part of the East Asia-Australia migratory corridor for migratory birds,as well as the only mid-temperate coastal wetland in China,which is of great importance for the function and productivity of temperate wetland ecosystems,etc.However,there are still few studies on the changes of the Yalu River estuary wetlands and longer time sequences.In order to deeply understand the spatial and temporal distribution and dynamic change characteristics of the wetlands in the Yalu River estuary in the past 40 years,this paper takes the Landsat series remote sensing images of 1980,1990,2000,2010and 2020 as the basic data source,extracts the information of land cover types in the Yalu River estuary based on the object-oriented random forest classification method to obtain wetland information,analyzes the 40-year change trend of wetlands in the Yalu River estuary by transfer matrix,mass center migration The study analyzed the 40-year change trend of wetlands in the Yalu River estuary through transfer matrix,mass migration and dynamic attitude models,and analyzed the dynamic change of wetland landscape pattern in the Yalu River estuary through landscape index,direct human interference and human activity intensity models,explored the correlation between natural factors and human activities on the change of wetland landscape,and quantitatively and qualitatively analyzed the influence of major driving factors on the change of wetland landscape in the Yalu River estuary.The results of the study are as follows.(1)The total area of wetlands in the Yalu River estuary showed a decreasing trend year by year between 1980 and 2020,and the rate of wetland loss was 13.2%;the rate of wetland loss and the area lost were both the highest between 2000 and 2010,at 5.1%and 37.8 km~2,respectively.the total area of wetlands on the Chinese side showed a decreasing trend year by year,and the rate of wetland loss was 15.1%;the rate of wetland loss and the area lost were both the highest between 2010 and 2020.The total wetland area on the Korean side showed a trend of decreasing,then increasing and then decreasing,with a wetland loss rate of 11.9%;the wetland loss rate and the area lost between 2000 and 2010 were both the highest,at 5.1%and 15.1 km~2,respectively.The area of artificial wetlands in the study area showed a trend of annual increase,with a rapid increase in artificial wetlands on the Chinese side between 1980 and 1990,and a rapid increase in artificial wetlands on the North Korean side between 2010 and 2020.(2)During the 40-year period,natural wetlands in the study area shifted to non-wetlands by 112.2 km~2,mainly to cropland and artificial surfaces,62.4 and 43.5 km~2,respectively;natural wetlands shifted to artificial wetlands by 17.9 km~2,and the center of mass of swampy wetland patches shifted to the sea by 1.4 km,with anthropogenic intervention driving the encroachment of swampy wetlands near the land.On the Chinese side,natural wetlands were transferred to non-wetlands by 55.2 km~2,mainly to artificial surfaces and arable land by 40.2 and 10.2 km~2,respectively;natural wetlands were transferred to artificial wetlands by 14.3 km~2,and the center of mass of marsh wetland patches was shifted towards the sea by 1.4 km;on the North Korean side,natural wetlands were transferred to non-wetlands by 57.0 km~2,mainly to arable land and artificial The natural wetlands in the Yalu River estuary are not conducive to maintaining the ecological integrity of the wetlands,and the protection of the wetlands in the estuary needs to be strengthened.(3)From the wetland landscape pattern index,the spreading degree index,aggregation degree index and maximum patch index of wetlands in the Yalu River estuary showed a decreasing trend during 40 years,while the Shannon uniformity index showed an increasing trend.It indicates that the overall dominance in the study area has decreased and evenly distributed,the connectivity between wetland patches has decreased,and the fragmentation has increased.From the landscape pattern index of each wetland type,we can see that the heterogeneity of swampy wetland patches in the study area increases,the landscape shape becomes complex,and the degree of fragmentation increases;the heterogeneity of natural water bodies increases,the landscape shape becomes complex,and the degree of landscape fragmentation first decreases and then increases;the heterogeneity of artificial wetlands decreases,the landscape shape changes from simple to complex,the degree of fragmentation of wetland landscape increases,and the ecological environment needs to be protected and further Optimization.(4)The results of the analysis of the drivers show that natural factors have less influence on the evolution of wetlands and anthropogenic activities are the main cause.Anthropogenic activities are obvious in the study area,and the rate of anthropogenic disturbance increased from 32.40%in 1980 to 41.81%in 2020 year by year,and the fragmentation of the landscape increased;except for 2000 and 2020,the rate of anthropogenic disturbance was higher on the Korean side.On the Chinese side,arable land expansion was the main factor for wetland loss before 2000,and the highest share was 67.4%;Artificial surface expansion was the main factor for wetland loss after 2000and accounted for up to 68.3%.Human activities caused 91.4%of the wetland loss on the Chinese side.Cultivated land expansion on the North Korean side dominated 97.5%of wetland loss.The area of wetlands occupied by cultivated land on the North Korean side is nearly 23 times larger than that on the Chinese side;while the area of wetlands occupied by artificial surfaces on the Chinese side is about 11 times larger than that on the North Korean side.This study addresses the environmental problems caused by the change and degradation of estuarine wetlands,enhances the analysis of the interannual spatial and temporal evolution patterns of Yalu River estuarine wetlands based on the characteristic changes of landscape patterns,and analyzes the drivers of wetland changes to provide some reference for understanding the dynamic evolution patterns of Yalu River estuarine wetlands and their causes,and helps relevant departments to take active and effective measures to strengthen the protection and restoration of Yalu River estuarine wetlands,with a view to providing data support and theoretical basis for the sustainable development of wetland ecosystems.