| Ecosystem service(ES)is the benefit that humans obtain from nature directly or indirectly,the bridge connecting the natural ecosystem and socio-economic system,and an important tool for the practice of ecological protection.However,there are some urgent problems to be solved,such as the lack of ES assessment on demand side,and the unclear current situation and influence mechanism of “Win-Win” mode(the situation that multiple ESs supply is at high value at the same time)and ES supply-demand relationship,which restrict ES’s application potential.How to carry out and strengthen the supply and demand assessment of ESs in key watersheds or regions,and reveal the spatiotemporal change,trade-off/synergy and supply-demand matching of ESs are the urgent task of ecosystem management and regional sustainable development.In this study,ESs and their spatiotemporal pattern and supply-demand relationship were systematically evaluated from the three aspects of “supply side”,“demand side” and “supply-demand relationship” from2000 to 2020.The main results are as follows:(1)On the supply side,aiming at the exploration of spatiotemporal pattern and the "win-win" mode of ESs,the In VEST model was used in this study to map the spatial distribution and dynamic of key ESs such as water yield,water purification,soil conservation,carbon fixation,habitat quality and food supply in the Yangtze River Basin from 2000 to 2020.Random forest model and spatiotemporal geographical weighted regression model were used to reveal the driving forces of ESs.ESs change and principal component analysis were used to compare and analyze the trade-off/synergy relationship of ESs from dynamic and static perspectives.Spatial overlay and logistic regression model were used to explore the possibility of "win-win" mode.Results showed that the impact of GDP and population density on water yield,soil conservation and carbon fixation showed a downward trend,and the impact on habitat quality and food supply showed an upward trend from 2000 to 2020.There were synergistic relationships among water yield,water purification,and food supply,while there were a trade-off relationship between water purification,food supply and habitat quality.The “Win-Win” region of ESs in the Yangtze River Basin was the high-value distribution area of water yield,soil conservation,carbon fixation and habitat quality,with an area of 281,840 hectares.It was mainly distributed in Zhangjiajie,Xiaogan,Wuhan,Jingdezhen,Shangrao,Yingtan and so on.Population density had a negative impact on the possibility of “Win-Win” mode.“Win-Win” region often occured in areas with low altitude,high rainfall,large slope and low temperature.(2)On the demand side,aiming at stakeholders preference and ES demand assessment,4580 valid questionnaires were conducted to investigate local residents’ preference for ESs in the Yangtze River Middle Reaches Megalopolis in this study.Probit model,multiple regression model,automatic linear model and random forest model were used to reveal the influence of individual socio-economic characteristics,environmental awareness and surrounding living environment on willingness to pay and perceived importance of ESs.Principal component analysis was used to identify the ESs demand bundle.A comprehensive assessment method of ES value on the demand side was proposed.Results showed that the average willingness to pay for ESs was 628 Yuan per person per year.Living environment factor was the most important predictor of willingness to pay for ESs,and its importance was much greater than individual socio-economic characteristics and environmental awareness.Three kinds of ES demand bundles were identified,namely green environment bundle,ecological stability bundle and grain service bundle.The total value of ESs on demand side of the Yangtze River Middle Reaches Megalopolis in 2000,2005,2010,2015 and 2020 was 883.1 billion,889.4 billion,862.5 billion,850 billion and 716.2 billion Yuan respectively.High value areas of ESs were mainly distributed in areas such as the boundaries of provincial capital(Wuhan,Changsha and Nanchang)and the boundaries of main water areas(Yangtze River,Poyang Lake and Dongting Lake).(3)From the perspective of supply-demand relationship,in consideration of localization characteristics and spatial heterogeneity of ES demand,the Yangtze River Middle Reaches Megalopolis,which is planned in the “14th five-year plan”,was selected as study area.The supply-demand ratio was used to identify the supply-demand situation of ESs(such as surplus,balance or deficit).Geographic weighted regression was used to reveal the impact of landscape pattern on ES trade-off and supply-demand relationship.Results showed that there were significant differences in spatial distribution,driving factors and trade-offs between supply and demand of water yield,water purification and soil conservation in the Yangtze River Middle Reaches Megalopolis.There were high trade-offs between water purification,soil conservation and water yield,and the trade-off degree on the supply side was greater than that on the demand side.Water purification in most areas of the Yangtze River Middle Reaches Megalopolis(except Wuhan,Changsha and Nanchang cities and near the main water areas)was in deficit.Maintaining and improving ecosystem diversity in the process of land urbanization will help to minimize the trade-off among water-related ESs and alleviate the deficit of water purification.To sum up,this study added important first-hand empirical data to the field of ES supply and demand assessment and supply-demand relationship.It enriches the contents and methods of ES supply and demand assessment,spatiotemporal pattern,tradeoff/synergy and supply-demand matching,and can provide data support and theoretical basis for the implementation of relevant policies such as Yangtze River Protection and ecological compensation,and the planning,management and utilization of regional ESs. |
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