| In the context of global climate change and rapid urbanization,natural disasters pose a serious challenge to sustainable socio-economic development,and the damage they cause depends not only on the frequency and intensity of natural drivers,but is also significantly influenced by the vulnerability characteristics of socio-economic disaster-bearing bodies.Currently,vulnerability studies have become a hot topic in field of natural hazard risk.Vulnerability as a property of socio-economic hazard-affected bodies changes with socio-economic development,institutional improvements,and changes in hazard-affected bodies.However,most of the current vulnerability studies are based on a particular year or a particular disaster event,and there is a lack of research on the spatial and temporal dynamics of vulnerability,as well as on the variability of the dynamics of indicators within vulnerability.Therefore,this paper constructs a social vulnerability assessment index system for coastal cities in China,which are disaster-prone and have a high concentration of economic and population,as the study area.Using the national population census data of 2000,2010 and 2020,statistical yearbook data of coastal provinces and cities and statistical bulletin data at all levels,the spatial patterns and changing trends of social vulnerability of Chinese coastal cities in the past two decades were quantitatively revealed through Arc GIS spatial analysis tools,and the spatial and temporal patterns of its different indicators and their variability were further studied,with the following main findings:(1)The overall social vulnerability of China's coastal cities in 2020 is dominated by lower levels,with economically developed areas showing even lower levels of social vulnerability.The social vulnerability scores for coastal cities in 2020 range from 0.35 to 0.62,with 39% of lower vulnerability classes and 30% of low vulnerability class areas;no cities are in higher and high vulnerability classes.Therefore,the social vulnerability of China's coastal cities in 2020 is dominated by lower grades.Spatially,social vulnerability is higher in the southern coastal areas than in the northern coastal areas,and lower in the Bohai Sea region in the northern coast,the Yangtze River Delta region in the central coast and the Pearl River Delta in the southern coast.Specifically for its secondary indicators,the demographic factor shows a distribution characteristic of "low in the northern coast,high in the southern coast,low in the Yangtze River Delta region in the central coast and the Pearl River Delta region in the southern coast".The distribution of the economic factor is "low in the Yangtze River Delta region in the central coast and the Pearl River Delta region in the southern coast";the distribution of the social factor is "high in the central and southern coast of the northern coast and low in the Shandong Peninsula in the northern coast and the Yangtze River Delta region in the central coast and the Pearl River Delta region in the southern coast".Thus,economically developed areas show lower social vulnerability;on the contrary,cities with low socio-economic levels show higher social vulnerability.(2)During the period 2000-2020,the level of social vulnerability of coastal cities in China decreases,with the deceleration slowing down significantly in the latter decade and the regional centre of faster deceleration gradually moving south.The number of cities with high and high vulnerability levels decreases,while the number of cities with low and low vulnerability levels increases.In terms of temporal trends,the deceleration in vulnerability in the first decade(2000-2010)does not coincide with the deceleration in the second decade(2010-2020),with the deceleration in vulnerability slowing down significantly in the second decade.Spatially,the faster deceleration in the first decade is concentrated in the Liaodong Peninsula,Bohai Sea Rim and Shandong Peninsula in the northern coast,the Yangtze River Delta in the central coast and the Pearl River Delta in the southern coast;the faster deceleration in the second decade is concentrated in the Shandong Peninsula in the northern coast,the Yangtze River Delta in the central coast,and the Pearl River Delta and Beibu Gulf in the southern coast.A certain degree of southward shift can be observed in the faster decelerating regions.(3)The three main factors of social vulnerability from 2000 to 2020 show different characteristics of spatial and temporal changes,and the population factor is not consistent with the overall trend of change.On the whole,the population factor shows a declining trend followed by an increasing trend,which is opposite to the overall trend of social vulnerability.The declining trend is mainly in the northern and southern coastal areas,while the central coastal areas show a declining trend.In contrast,the economic and social factors of vulnerability show a decreasing trend year on year,with the central coastal region showing the greatest deceleration in the economic and social factors.Spatially,the economic and demographic factors show different spatial characteristics from the social factors,with the demographic and social factors showing a spatial characteristic of "higher in the south than in the north" in all three years,and the economic factors showing a spatial characteristic of "lower in the central coastal areas and higher in the north and south coastal areas".(4)The spatial characteristics of social vulnerability in Chinese coastal cities in2000,2010 and 2020 are aggregated,with the degree of aggregation increasing and the spatial differences decreasing each year.The global Moran index of social vulnerability in Chinese coastal cities in 2000,2010 and 2020 is 0.34(p<0.05),0.55(p<0.05)and0.57(p<0.05)respectively,which are all greater than 0 and increasing every year,indicating that social vulnerability in Chinese coastal cities has the spatial characteristics of aggregation,and the degree of aggregation increases every year.From the results of the local spatial autocorrelation analysis,the number of cities clustered in the positively correlated spatial pattern("high-high" and "low-low")is greater than that in the negatively correlated spatial pattern("high-low").The number of cities in the positively correlated spatial pattern is increasing,while the number of cities in the negatively correlated spatial pattern is stable.It is noteworthy that the number of cities in the " high-high" clusters has increased each year,indicating a greater concentration of cities with relatively high social vulnerability,which requires a regional perspective on social vulnerability governance.This paper has developed a social vulnerability assessment indicator system for coastal cities,and has assessed the social vulnerability of Chinese coastal cities in 2000,2010 and 2020,and explored their spatial and temporal variability from a dynamic perspective,further focusing on the differences in the spatial and temporal dynamics of the population,economic and social vulnerability factors.The results of the study show that social vulnerability in coastal cities in China has shown a clear downward trend over the past 20 years,but the trends of different vulnerability indicators are not consistent,especially in the northern and southern coastal areas,where the population vulnerability indicator also shows a decreasing trend followed by an increasing trend,which needs to be taken into account in comprehensive disaster prevention and mitigation.Spatially,the number of cities in the 'high-high' cluster is on the rise,which poses a challenge for regional disaster risk management and requires a regional perspective and approach to governance.Although the overall social vulnerability of coastal cities in China is low,the spatial and temporal variation of social vulnerability,especially the variation of different vulnerability indicators,deserves further attention,which is of great significance for local planning of disaster prevention and mitigation to reduce social vulnerability. |
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