An Extended Framework For Fresh Water-related Ecosystem Services Flows And Its Application On Social-Ecological System

As the most important and supportive natural capital,freshwater has provided various ecosystem services such as water purification and freshwater supply that are regarded as the key to realize other ecosystem services.However,dramatic climate change and land-use change is worsening freshwater crisis(i.e.,water scarcity,water pollution,water-related disasters,and water degradation)via altering watershed processes,which have induced overwhelming impacts on water-relative ecosystem services.To achieve water resource sustainability and obtain continuous water-related ecosystem services,it is vital to figure out the mechanism underlying ecosystem services’ production,delivery,and beneficiaries-based demand within Social-Ecological Systems.Being supportive of the field monitoring data,hydrological models,historical observations data,and social-economic models,we first extended the water-related ecosystem services flows framework.Subsequently,we distinguished the impacts of land use change on freshwater ecosystem service flows in terms of water supply and demand in Aojiang River watershed,and finally we illustrated the complex interactions of natural capital,built/human capital,beneficiaries,and the site-specific flows of water-related ecosystem services.Our results showed that:(1)The framework of water-related ecosystem services flows could be extended by integrating water quantity and quality,and capturing the flows of ecosystem services(i.e.,green phase)and degraded ecosystem services(i.e.,red phase),and connecting natural capital,built/human capital,and beneficiaries.(2)Rapid urbanization between 1991 and 2015 in Aojiang River watershed led to a minor increase of 2.5%in the supply of freshwater ecosystem services.However,demand increased by 96.3%in downstream areas whose demand for freshwater increased substantially due to large shifts in agricultural,urban,and industrial activities,leading to a 25.7%overall decrease in freshwater ecosystem services flows.(3)The interactions of natural capital,built/human capital,and beneficiaries play an important role in the ecosystem service flows.During the green phase,the interactions of natural capital and built capital significantly improved water quality in downstream areas with higher flows in Jiulong River watershed.During the red phase,built capital reduced nitrogen by～10%while natural capital further reduced it by over one half,which improved the water quality of degraded ecosystem services.Our study provides explicit information on freshwater ecosystem services flows from suppliers to beneficiaries,and back to suppliers within watershed,which can provide information for land use planning,natural capital management,source-to-sea management,eco-compensation,and pollutant management both at local and regional scales,thus facilitating integrated watershed management and decision making,and promoting the sustainability of freshwater ecosystems.