| The increasingly severe contradictions between human and nature systems have drawn worldwide attention to exploring the mechanisms of the coupled human and natural systems,especially in urban agglomerations in the fast-growing developing country.The rapid urbanization in urban agglomerations has severely disturbed the ecosystem health status,which has threatened regional sustainability.Systematic analysis of the impact of urbanization on ecosystem health in urban agglomerations has significant implications for urban landscape planning and policymaking.However,the assessment of ecosystem health is still incomplete,and the influence mechanisms of urbanization on ecosystem health remains unclear.Under this context,this study attempts to fill these gaps by examining the ecosystem health with various models and multisource data and identifying the influence mechanism of urbanization on ecosystem health with an integrated spatial approach at multiscale.The objectives of this study are as follows:To determine the spatiotemporal patterns of comprehensive ecosystem services index at the county and town levels in the MRYRUA from 1995 to 2015.The comprehensive ecosystem services index in this study are measured by the grain productivity,water yield,carbon storage,soil conservation,water purification,biodiversity conservation,and cultural services supply with analytic hierarchy process.To determine the spatiotemporal patterns of ecosystem physical health at the county and town levels in the MRYRUA from 1995 to 2015.The ecosystem physical health is mainly measured by ecosystem organization,ecosystem vigor,and ecosystem resilience.To measure the spatiotemporal patterns of ecosystem health at the county and town levels in the MRYRUA from 1995 to 2015.Ecosystem health is primarily characterized by linking ecosystem services and landscape patterns in the assessment of ecosystem health.To identify the spatial determinants of ecosystem health with an integrated spatial approach at the county and town levels,in particular,the impact mechanisms of urbanization on ecosystem health.This study attempts to solve the following four questions:How to build the ecosystem health assessment framework based on ecosystem services and landscape patterns?What are the spatiotemporal evolution patterns of ecosystem services and ecosystem physical health at the county and town levels in the MRYRUA from 1995 to 2015?What are the spatiotemporal evolution patterns of ecosystem health at the county and town levels in the MRYRUA from 1995 to 2015?How can we comprehensively and effectively evaluate the spatial impact of urbanization on ecosystem health at the global and local levels of the county and town scales?The main conclusions of this study are as follows:Regarding the assessment results of comprehensive ecosystem services index,the average values of comprehensive ecosystem services in the MRYRUA in 1995,2000,2005,2010,and 2015 are respectively 0.452,0.438,0.442,0.439,and 0.443,documenting an overall decreasing trend during the study period.The comprehensive ecosystem services indexes in the Dabie Mountains north of and the Wu Mountains west of Hubei Province,the Xuefeng Mountains midwest of Hunan Province,the Nanling Mountains south of and the Wuyi Mountains east of Jiangxi Province,and the Luoxiao Mountains between Jiangxi and Hunan Provinces are above 0.50,and the counties or towns in the Jianghan,Dongting Lake,and Poyang Lake Plains;the Wuhan and Changsha-Zhuzhou-Xiangtan Metropolis,and Poyang Lake City Group,especially the counties or towns around some of the major cities in these plains exhibit obviously lower comprehensive ecosystem services index.The comprehensive ecosystem services indexes in the plains areas counties decrease significantly,especially in the core counties or towns,such as Wuhan,Changsha,and Nanchang.Regarding the assessment results of ecosystem health,the results indicate that the overall ecosystem health indexes exhibit a gradually decreasing trend during the period studied,documenting that the ecosystem health status in the MRYRUA deteriorates from 1995 to 2015.The average value of ecosystem health is set as the ordinary health status in the MRYRUA.The proportion of counties that below the average value of ecosystem health during the study period are respectively 55.07%,54.59%,53.62%,54.11%,and 52.17%,while the proportion of towns that below the average value of ecosystem health during the study period are 53.22%,53.78%,53.78%,53.33%,and 53.22%,respectively.More proportion of towns and counties are below the ordinary health status in the MRYRUA.In terms of the spatial distribution of ecosystem health,we can find significant spatial heterogeneity.The ecosystem health index in the Jianghan Plain,Dongting Lake Plain,counties or towns around Wuhan,Changsha,and Nanchang are mostly below 0.35.The ecosystem health index in the surrounding mountainous counties or towns is above 0.65.Additionally,the ecosystem health index along the main traffic routes are also lower than in other areas.I can conclude that terrain conditions,traffic conditions,location conditions,economic levels,and ecosystem health are closely related.Furthermore,I find that the ecosystem health around the main cities,such as Wuhan,Changsha,and Nanchang experiences more severe deterioration of ecosystem health.Regarding the assessment results of urbanization,the evaluation results indicate that the urbanization levels during the study period show a gradual increase tendency because of the constantly expanding of developed land,continuous increase of population density and GDP density.The counties or towns with higher urbanization levels are mainly concentrated in the core areas of the key cities in the MRYRUA,especially the counties or towns around Yichang,Wuhan,Changsha,and Nanchang,demonstrating a decreasing trend from the center of these cities to their outer periphery.The spatial pattern of population growth,economic growth,and land expansion shows a high degree of consistency around the key cities in the MRYRUA.The inconsistency of these three indicators can be found in suburban areas.The values of GDP density and population density decrease from the urban center to the periphery gradually,while land expansion in suburban areas show relatively higher values.The common issue can also be found in the MRYRUA—economic urbanization and population urbanization has lagged behind the land urbanization.The relationship between ecosystem health and urbanization parameters(population density,GDP density,developed land proportion,and comprehensive urbanization)exhibits an "U" shaped relationship at both county and town levels,documenting that the development of urbanization would deteriorate ecosystem health,while urbanization would promote the ecosystem health when urbanization reaches a certain level.Regarding the influence mechanism of urbanization on ecosystem health,the negative global bivariate Moran's I values between ecosystem health and urbanization indicate that,overall,urbanization causes the degradation of ecosystem health.According to the regression results of global regression models,I can find that ecosystem health is negatively associated with urbanization in all models at both scales,and the impact of urbanization level on ecosystem health gradual weakens.The regression coefficients of urbanization level-squared are all positive,further indicating that a U-shaped relationship is found between ecosystem health and urbanization.The symmetry axis in 1995,2000,2005,2010,and 2015 at county level are 0.334,0.293,0.313,0.364,and 0.459,while symmetry axis in 1995,2000,2005,2010,and 2015 at town level are 0.656,0.780,0.603,0.520,and 0.500,respectively.Additionally,land use intensity is identified negatively associated with ecosystem health,while precipitation,terrain relief,and distance to rivers are positively associated with ecosystem health.The spatial lag terms are significant in SEMLD at both levels except models in 2010 and 2015 at the county level,indicating that the spatial spillover effect of ecosystem health is common in the MRYRUA.In the town level,every town gains 0.118%,0.129%,0.149%,0.152%,and 0.161%for each percentage point of weighted ecosystem health increase in its neighbors,respectively.The 0.118%,0.129%,0.149%,0.152%,and 0.161%growth of ecosystem health do not originate from "organic"growth but evolves as a "gift" from its neighbors.Regression coefficients of urbanization on ecosystem health vary greatly in different urban agglomerations.Overall,I find that the effects of urbanization on ecosystem health gradually weaken in all urban agglomerations.The urbanization in Yichang-Jingmen-Jingzhou urban agglomerations disturbs the ecosystem health the most,while the impact of urbanization on ecosystem health is the weakest in Wuhan megalopolis at the both levels according to the spatial regime SEMLD.The impact of urbanization on ecosystem health is the weakest in the district-level cities and strongest in the county-level cities unit at both levels.The spatially non-stationary response of ecosystem health to urbanization is examined in the GWR model,the effects of urbanization on ecosystem health vary spatially in the different periods.I also find that the GWR results are scale-dependent and scale effects are particularly significant in kernel bandwidth of weight determination and block scale of pattern analysis.The findings in this study provide important implications for urban planning and ecologically oriented policymaking in the MRYRUA. |
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