Network synergistic analysis of water-related ecosystem services in the Dongjiang River Basin, China

Ecosystem services (ESs) constitute essential ecological capital that supports human well-being and underpins regional sustainable development at the sub-catchment scale. The provision of these services is influenced by the availability of water resources and shaped by spatiotemporal hydrological variability. In the context of global climate change and intensified urbanization, quantifying the dynamic equilibrium of water-related ESs has become a central challenge in sustainability science. Despite growing interest, substantial knowledge gaps remain regarding the spatiotemporal evolution of water-related ESs and their interactions within network structures. This study focuses on the Dongjiang River Basin, a critical water source for major metropolitan regions including Shenzhen, Hong Kong, and Dongguan, to evaluate the combined impacts of water quantity and quality on ecosystem functioning. Four principal water-related ESs are examined. Employing the InVEST model, along with statistical analyses, we assessed the trade-offs and synergies among these services and constructed an ecological service network at the sub-watershed scale from 2000 to 2020. Results indicate a general decline in water-related ESs, accompanied by pronounced spatial heterogeneity. A total of 218 ES networks were identified across 224 sub-catchments, classified into seven types and 27 subtypes according to service node composition and the presence of dominant nodes. Networks with balanced service node development accounted for 34.8%, while those dominated by one or two key services comprised 65.2%. This suggests that interconnections among ESs are often concentrated within specific sub-watersheds. Water yield frequently exhibited trade-offs with other services, thereby increasing structural complexity within the network. Over time, the region's ecosystem service network has transitioned from diversified functions to a structure primarily driven by soil conservation and water purification. These findings highlight the importance of prioritizing restoration efforts in urbanized sub-catchments, particularly those with critical demand for water purification and soil retention functions.