Implications of spatial priority areas for hydrological ecosystem services through coupling hydrology model and Zonation model under different economic costs of water utilizations in northernmost of Japan

Although the importance of addressing economic values of ecosystem services in ecological planning and decision-making is evident, substantial practical challenges still remain. In particular, methods to identify spatial priority areas for the provision of hydrological ecosystem services across watershed need to be developed. Spatial priority areas are those locations which provide high benefits from one or more ecosystem service. Here we mapped a set of ecosystem services from hydrology model (Soil and Water Assessment Tool) and delineated priority areas from Zonation model according to different economic cost layer scenarios. Each economic cost layer scenario was produced by a set of water yields allocated to different utilizations for socio-economic development and corresponds to different water resources exploitation strategies which different stakeholders could undertake. Using the northernmost of Japan (Teshio watershed) as a case study, we processed grid maps of key individual and multiple ecosystem services including water yield, and inorganic and organic nutrient retentions, and also explored their spatial distribution patterns. Finally, we showed spatial priority areas for individual and multiple hydrological ecosystem services using different economic cost layers which corresponded to different water resources utilization. Our results are as follows: (i) there were two main spatial distribution patterns of ecosystem services in this study site, water yield, and organic nutrient and sediment retention services (concentrated in northern, southeastern and southwestern locations of study watershed) and inorganic nutrient retention services (concentrated in agricultural lands and riparian areas); (ii) tremendous changes took place in the spatial patterns of priority areas for individual and multiple ecosystem services with considering different economic costs; (iii) it is important to simultaneously consider individual and multiple ecosystem services under different economic costs in identifying spatial priority areas. Different economic cost layer scenarios provoke drastic changes in the delineation of priority areas, and therefore decision-making processes need to carefully consider the relative economic values attributed to different services for regional ecosystem management and planning.