Mapping connected freshwater ecosystems for conservation and restoration planning across China

Freshwater ecosystem conservation is critical for biodiversity maintenance, ecological stability, and climate regulation, yet conventional conservation strategies predominantly focus on isolated aquatic components including rivers, lakes, and wetlands, while neglecting adjacent terrestrial landscapes that underpin aquatic ecological processes and landscape connectivity. This study developed a nationwide systematic framework to delineate spatially connected freshwater ecosystems across China and formulate differentiated, targeted ecological management and restoration priorities to address this research gap. Three alternative delineation scenarios were adopted in the national-scale mapping, with the mapped extent of freshwater ecosystems accounting for 40.41% to 50.85% of China’s total land area, showing significant spatial heterogeneity across major river basins of the country. Based on the intermediate delineation scenario, the research evaluated regional ecological health status and fish species richness with basin-specific threshold standards, further classifying China’s connected freshwater ecosystems into four distinct management zones. Statistical results show that the ecological maintenance and monitoring zone constitutes the largest proportion at 47.27%, followed by the environmental management zone (18.64%), conservation and restoration zone (18.19%), and priority conservation zone (15.90%). For the two intervention-dominant zones (environmental management zone and conservation and restoration zone), connectivity enhancement is identified as the core management priority, covering 78.10% of their combined land area. Furthermore, this study quantified the climate mitigation co-benefits of freshwater ecological restoration. For the 1.37 million hectares of restoration land with accessible forest-regrowth carbon data, the annual carbon dioxide removal capacity reaches 7.97 Mt CO₂, with a cumulative 30-year carbon sequestration potential of 239.08 Mt CO₂. Notably, 54.4% of the total carbon sequestration benefit is concentrated in the Yangtze River Basin, highlighting its key role in national freshwater ecological restoration and climate mitigation. By comprehensively integrating multi-dimensional ecological indicators, including ecosystem spatial extent, regional ecological health conditions, biodiversity conservation importance, and dominant anthropogenic and natural ecological pressures, this research provides a scientific, operable, and nationwide spatial basis for refined freshwater ecosystem conservation, targeted ecological restoration, and adaptive watershed management in China. It also verifies the significant climate mitigation co-benefits of freshwater ecological protection and restoration, offering valuable references for synergistic ecological conservation and carbon neutrality strategy implementation at the national basin scale.