A Study On The Spatiotemporal Pattern And Exposure Of Population And GDP In The Coastal Lowlands Of The Yangtze River Delta From 1990 To 2100

Low elevation coastal zones(LECZ)include large deltas and coastal plains that are often densely populated and economically developed.The LECZ are increasingly at risk due to climate change and sea level rise.Among all deltas in the world,the Yangtze River Delta has the fourth largest coastal lowland area and the second largest population.It can be said that the Yangtze River Delta coastal lowlands are a critical and sensitive area for the impacts of climate change and sea level rise,and the compound risk of coastal flooding and sea level rise facing the LECZ of Yangtze River Delta is increasing in the 21 st century,driven by climatic and non-climatic factors(population and asset growth,urbanization,land use change,etc.).Focusing on the LECZ of the Yangtze River Delta,this paper uses spatialized population data,long time series GDP data,and DEM and extreme water level data to study the spatial and temporal changes of population and GDP in the LECZ of the Yangtze River Delta from 1990 to 2100,considering climate change and sea level rise scenarios,to clarify the exposed population and GDP in the LECZ The spatial and temporal dynamics of current and future changes of exposed population and GDP in the LECZ,analyze the changes of population and GDP exposure under different sea level rise scenarios,identify highly exposed areas,and quantitatively analyze the contributions and drivers of climatic and non-climatic factors to provide a theoretical basis and methodological reference for climate change adaptation and disaster risk management in the Yangtze River Delta and other LECZ.Major contributions and findings of this study are as follows.(1)The population of the LECZ of the Yangtze River Delta was 103.94 million in2015,an increase of 29.285 million(39.2%)from 1990.the total GDP value of the coastal lowlands was 10.26 trillion yuan in 2015,accounting for 72.40% of the coastal provinces and cities in the Yangtze River Delta.Rapid urbanization has led to increased spatial heterogeneity of population and GDP.The ratio of population and GDP in nearcoastal and low-altitude areas is large and growing fast,and the population is moving toward the coastline.(2)In the 21 st century,the population in the LECZ of the Yangtze River Delta shows a first increase and then decrease,which is different from the global trend of population growth in the coastal lowlands.The LECZ of the Yangtze River Delta population estimated based on five shared socio-economic paths shows an increasing trend up to 2040,with a maximum population of 131.85 million,and then a decreasing trend,but the proportion of coastal lowland population increases from 71.1% in 2040 to 73.7% in 2100,while the GDP shows an increasing to stabilizing trend.(3)The exposed population of coastal flooding of the LECZ in the Yangtze River Delta is 76.12 million in 2015,which will increase to 85 ~ 10 million by 2050 and decrease to 55 ~ 63 million by the end of this century(2100).the exposed GDP of coastal flooding of the LECZ in the Yangtze River Delta is 0.16 trillion yuan in 2015,which will increase to 100 ~180 trillion yuan,and by the end of this century(2100),it will increase to 130-230 trillion yuan.(4)From 2015 to 2100,the contribution of sea level rise in the LECZ of the Yangtze River Delta to population exposure continues to increase,while the contribution of population change to population exposure continues to decrease.With climate change and sea level rise,the flood risk in the LECZ will further increase,and the spatial differences in risk and risk hotspots will become more prominent.The rapid population growth in the LECZ of the Yangtze River Delta and the shift of the population center of gravity toward the coastline significantly increase the risk of weatherization and sea level rise.At the same time,the continuous population aggregation and spatial heterogeneity will continue to increase,requiring different strategies and adaptation paths for adapting to sea level rise and managing flood risks for different population density zones in the LECZ and spatial and temporal evolution trends of population in the 21 st century.