Ecological carrying capacity and vulnerability evaluation of coral islands in the South China Sea

Abstract Coral islands in the South China Sea have unique geographical locations and low ecosystem stability. Studying the impacts of human activities and climate change on the ecological environment is crucial for achieving the sustainable development of coral islands. In this study, Dongsha Island, Yongxing Island, Taiping Island and Nanwei Island are selected as the study areas, and an evaluation index system is innovatively constructed with 26 factors including climate data, land resources, environmental conditions, and socioeconomic data. The entropy weight-based technique for order preference by similarity to an ideal solution model (TOPSIS), a coupled coordination degree model, and an obstacle degree model are used to conduct a comprehensive evaluation of the changes in the ecological carrying capacity (ECC) and ecological vulnerability (EV) in the study areas at various stages of island construction. The results show that the current ECC in the study areas is relatively low, mainly ranging between 0.2 and 0.4. The EVs of Yongxing Island and Taiping Island are more serious than those of Dongsha Island and Nanwei Island, showing a year-by-year increasing trend, and both exceeded 0.4 reaching a moderate vulnerability level in the late stage of construction. The level of coordinated development among the subsystems of the ECC and EV in the study areas is low, generally lying at the boundary between coordination and imbalance, with the primary obstacles to ECC and EV coupling concentrated in the resource support subsystem and the ecological pressure subsystem, respectively. This paper presents a comprehensive comparative study of coral islands in the South China Sea for the first time and advises to implement ecological restoration projects to mitigate the negative impacts of human factors on the ECC and EV and to enhance the exploration of ecological resource conservation models. This study contributes to long-term monitoring of the ECC and EV of coral islands in the absence of field data and provides a reference for the future development of coral islands and corresponding resource allocation.