Evaluating the effectiveness of marine ecological restoration in Xiamen Bay: A three-dimensional ecosystem-based...

Marine ecosystems are undergoing unprecedented degradation, making ecological restoration an essential active intervention to mitigate this decline. In recent years, Xiamen has continuously advanced multiple types of bay ecological restoration projects, accumulating substantial practical experience. From an ecosystem perspective, this study develops a three-dimensional evaluation framework encompassing ecosystem pattern, ecosystem quality, and ecosystem function. Coastal blue carbon indicators reflect the spatial distribution of mangroves and other coastal vegetation; dissolved oxygen and chemical oxygen demand represent improvements in water quality; and coastal vulnerability indicators measure the ecosystem's capacity for disaster prevention and mitigation. Using 2003, 2013, and 2023 as reference years, we systematically evaluated the ecological restoration outcomes in Xiamen Bay over the past two decades. The results show that ecological conditions in the Jiulong River Estuary, Huandong Sea Area, and Eastern Sea Area improved significantly from 2003 to 2013. From 2013 to 2023, restoration effects became more pronounced in the Western Sea Area, Huandong Sea Area, and Eastern Sea Area, while restoration in the Dadeng Sea Area lagged due to human disturbances. Quantitative analysis indicates that restoration effectiveness increased by 60.4 % between 2003 and 2013, and by 23.6 % from 2013 to 2023, with an overall improvement of 98.2 % across the 20-year period. These findings highlight the long-term positive impacts of ecological restoration. Future efforts should focus on strengthening resilience in climate-vulnerable areas, enhancing long-term water quality monitoring and dynamic evaluation, and advancing the integration of restoration with infrastructure development to ensure sustainable and effective outcomes.