Abstract: Reclamation, as one of the main means for humans to utilize the ocean, with consequences on economic development in coastal areas. However, it might have adverse impacts on the ecological environment of coastal wetlands, thereby threatening the sustainable development. We investigated the impacts of reclamation on the ecological services of wetlands in Yangtze River Delta (Yancheng wetland) and the Yellow River Delta. Based on the area and attribute characteristics of various reclamation types, we constructed an ecological integrity damage index (ED) to estimate the ecological service value (ES), the thresholds of critical and abrupt change, as well as the changes in ecological services. The results showed that mangrove coastal wetlands had the highest total ES value, followed by estuarine waters, salt marsh nearshore waters, and tidal flats. Ecological services showed the strongest correlation with hydrological connectivity. Based on the relationship between ED and ES, reclaimed wetlands could be classified into four phases: compensatory phase (reclamation ratio 0-6.23%), accelerated decline phase (reclamation ratio 6.23%-40.08%), decelerated decline phase (reclamation ratio 40.08%-93.38%), and out-of-control phase (reclamation ratio 93.38%-100.00%). The degree of ecological integrity damage in salt marsh ecosystems increased with decreasing proportional area of reclamation types. The optimal reclamation combination model proposed in this study, which minimizes ecological service value loss, can provide scientific guidance for establishing wetland ecological service function assessment methods and revealing the dynamics of ecosystem services under reclamation.

Key words: coastal reclamation, ecological integrity damage index, ecological service function, threshold