Identifying The Spatial-temporal Patterns Of Prioritization For Conserving Water-related Ecosystem Services Under Climate Change

As a special ecological resource,water is the foundation that supports the entire life system of the earth.Globally,it provides multiple environmental values.Climate change caused by human activities may greatly affect water quality and quantity,and its negative effects directly or indirectly lead to the reduction of ecosystem services provided by ecosystems.Water ecosystem services are highly related to social development because of their role in human well-being.Therefore,it is necessary to implement spatial priority protection planning for water ecosystem services for stakeholders to mitigate the negative impact of climate change on ecosystem services.In this study,by integrating the quantitative assessment of water ecosystem services and system protection planning methods,and identifying the priority areas based on the quantified three water ecosystem services(water flow regulation,water purification,and erosion regulation services),the priority areas were analyzed by the landscape index analysis method.The degree of aggregation was evaluated,and then the redundancy analysis(RDA)method was used to identify the key factors of water ecosystem services,the selection of priority areas,and the impact of climate change on the division of priority areas.Firstly,the SWAT(soil and water assessment tool)model was used to quantify and visualize the water ecosystem services of the Xiangjiang River Basin(XRB).The SWAT model database of XRB was constructed.Four relevant indicators of water ecosystem services(water yield,sediment production,organic nitrogen,and organic phosphorus production)were simulated,based on the baseline climate scenario(1997-2015),mid-term climate scenario(2050),and long-term climate scenario(2070).The spatial pattern of each ecological indicator under different seasons had no obvious changes,but the average value of th ose indicators during the wet seasons was three to four times that of the dry seasons.Under the three climate change scenarios,the spatial distribution of water production changed most obviously,and the spatial distribution of organic nitrogen and phosphorus production was similar to sediment production.Secondly,building a protection planning model for the ecosystem service system of XRB: set the protection target of the MARXAN model,took the Gross Domestic Product(GDP)of the XRB as the protection cost,and combined the protection objects with the relevant indicators of the water ecosystem services exported by the SWAT model.The optimal plan of the priority areas under different climate scenarios was obtained.Under the climate change scenario,the planning unit selection frequency of high-altitude forestland areas in the upper and middle reaches of the Xiangjiang River was higher than in other areas,which means that these areas had higher conservation value.Finally,applying redundancy analysis to clarify the correlation of environmental factors.According to the output of the SWAT-MARXAN framework,RDA was used to further discuss the impact of relevant social-environmental factors on the selection of ecosystem services and their priority areas,and to clarify the selection of various environmental factors for the priority area selection of relevant water ecosystem services in XRB.In XRB,rainfall and temperature were the two key environmental factors for priority areas selection;runoff regulation services had a good correlation with climate change,and played a leading role in determining priority areas for water ecosystem services.Over time,the spatial protection efficiency of priority areas decreased from 1.264 to 0.867,indicating that climate change had a negative impact on selected priority areas under certain protection targets.Based on the research framework,the spatial distr ibution of water ecosystem services in XRB under future climate change scenarios had been effectively evaluated.A variety of priority management programs were identified by integrating socio-economic and environmental factors.It also provided useful info rmation for stakeholders and policy makers to assess environmental sensitivity,and developed a systematic conservation planning to face with climate change.