Study On The Impact Of Urbanization On The Value Of Ecosystem Services In Sichuan Province Based On County Scale

The development of urbanization has not only driven rapid socio-economic development,but also profoundly influenced the structure and processes of ecosystems,which in turn affects the ability of ecosystems to provide various services.A large number of researches have clarified the relationship among urbanization and ecosystem service values（ESV）in eastern China,however,the stage characteristics,specific spatial relationships and the existence of spillover effects between urbanization and ESV in western China are still not very clear.As an important province in the western region of China,Sichuan Province is a key component of the ecological protection barrier in the upper reaches of the Yangtze and Yellow Rivers,and an important water-conserving area,residing in a critical position in the national ecological security pattern.It is of strategic importance to understand and grasp the mechanisms of urbanization on ESV in Sichuan Province to promote high-quality regional development and maintain economic development and ecological balance.In this paper,183 counties in Sichuan Province were used as research objects,and the spatial and temporal adjustment factors of net primary productivity,precipitation and soil conservation were used to dynamically correct the equivalents,and then quantitatively estimated ESV.Secondly,a comprehensive evaluation index system of urbanization level was constructed from three dimensions of population,economy and land with the help of entropy method to measure the population,economy,land and comprehensive urbanization level in Sichuan Province.Then,the spatial and temporal evolution characteristics of urbanization and ecosystem service values were analyzed using GIS spatial analysis.Finally,the Geographically and Temporally Weight Regression Model（GTWR）and spatial panel econometric models were used to reveal the spatial and temporal divergence patterns and spillover effects of urbanization on ESV,and relevant recommendations were put forward to promote the coordinated development of the region.The results indicate that:（1）ESV shows a fluctuating downward trend in Sichuan Province,with an overall decrease of 2064.64×10~8 Yuan from 2000 to 2018,especially the value of forest,grassland,farmland and water decreasing most significantly,by 1204.45×10~8 Yuan,195.48×10~8 Yuan,408.30×10~8 Yuan and 274.34×10~8 yuan.In terms of service types,hydrological and climate regulation services decreased the most,by 719.99×10~8 yuan and 396.29×10~8 yuan,respectively.In addition,except for desert and wetland,the value of major service types provided by ecosystem per unit area decreased significantly,such as climate regulation service of forest and grassland decreased by 19.49×10~4 Yuan/km~2and 2.77×10~4 Yuan/km~2,respectively.Spatially,the total ESV shows a distribution characteristic of low in the east and high in the west and ESV per unit area shows a characteristic of low in the west and high in the east.The impairment of ESV in the eastern part of Sichuan is significantly higher than that in the western part.（2）The urbanization level in the east and west of Sichuan province is significantly different and the urbanization level in the eastern region is significantly greater than that in the western region,and the urbanization development is uneven.In terms of different types of urbanization,in 2018,counties with population,economy,land and comprehensive urbanization at the medium level and above accounted for65.57%,91.80%,53.55%and 87.43%of all counties,respectively,an increase of54.64%,88.52%,32.24%and 63.39%compared with 2000,with population and economic urbanization significantly faster than land urbanization.Comprehensive urbanization and other types of urbanization show differences in characteristics in different years and regions.（3）The Global Moran’s I index between county urbanization and ESV is basically greater than 0.5,with p-values less than 0.001 and z-values greater than the critical value of 1.96.There are obvious clustering and strong spatial and temporal divergence between the two,especially in the eastern and western counties of Sichuan Province.（4）There is a clear spatial and temporal heterogeneity in the impact of urbanization on ESV,which means that there is variability in the impact and direction of urbanization on ESV across counties in different study years.There is also variability in the impact of different dimensions of urbanization and integrated urbanization on ESV,with counties accounting for more than 80%of the negative fit coefficients for land and integrated urbanization,which have a consistently strong negative effect on ESV.Population urbanization shifted from a facilitating to a suppressing effect since2010,and economic urbanization shifted from a suppressing to a facilitating effect in2018.Spatially,the negative effect of urbanization on ESV is significantly higher in eastern Sichuan than in western Sichuan.（5）Population,economic,and land urbanization in each county had significant inhibitory effects on ESV in this county,with direct effect values of-0.67,-0.64,and-1.59,respectively,and the influence of land urbanization was significantly greater than that of population and economic urbanization.The p-values of indirect effects of economic and population urbanization were greater than 0.1,and the impact of urbanization on the surrounding counties was not very significant.The indirect effect value of land urbanization is-11.40 and p-values is less than 0.01,and there is a significant spillover effect on ESV,implying that the development of land urbanization in this county will not only inhibit the development of ESV in this county,but also show a strong inhibitory effect on neighboring counties.