Optimization schemes for the spatially explicit management of small watersheds based on ecosystem disservices

Reasonable planning of spatially explicit management measures is key to effectively achieving management goals. In this study, we adopted a spatial conservation prioritization method, which combines functional zoning, ecosystem disservice bundles, and existing management measures, with the aim of developing optimal deployment plans in six small watersheds in northwestern Beijing. First, we investigated the existing management measures in the study areas and recorded their sizes, scopes, and effectiveness. Second, according to the management priority, we ranked pixels representing the study area with the Zonation 4.0 platform. The process is based on the ideas of both spatial conservation prioritization and how the seven ecosystem disservices (sediment export, nitrogen and phosphorus pollution export, surface runoff, quick flow, and risks of collapse and debris flow) distribute spatially. Finally, we moved the existing management measures to suitable higher priority locations by matching the management priority rank indicated by the pixels, the functional zoning, which represents the main environmental problems, and the land use/cover types. Additionally, the changes in the ecosystem disservices were evaluated before and after the optimization operation. The results showed that the pixels with a higher management priority were located mainly in the plain areas and the junctions of the mountains and the plains, where the main environmental problems were water pollution and quick flow. Most of the management measures, such as percolation drainage ditches and greening, were moved to the plains in the optimization scheme. The extents of the decreases in five ecosystem disservices (sediment export, nitrogen and phosphorus pollution export, surface runoff, and quick flow) after optimization exceeded 90% in the study areas. This study provided a method to develop the plans of spatially explicit management measures for watersheds, the application of which ensures a scientific basis for management planning. Widely applying this method would improve the effectiveness of spatial management measures.