Tradeoffs between reducing flood risks and storing carbon stocks in mangroves

Mangrove habitats are important carbon(C) reserve sites. However, the overgrowth or overexpansion of mangroves may increase the risk of flooding, thus affecting human wellbeing. To decrease the flood risks, partial mangrove removal has been proposed as a managerial action, which would decrease the C stocks. Using the Danshuei River as a case study, the objective of this study was to determine the optimal removal area to allow the mangroves to meet the demands of reducing the loss of mangrove C stocks and adequately controlling the flood risks. Our results show that the ratios of the effective reduction in flood level (benefit) and the loss of mangrove C stocks (cost) were only higher under the condition of the removal of aboveground structures of mangrove trees than the ratios under the condition of the removal of both above- and belowground structures. The highest ratio of the effective reduction in flood level and the loss of mangrove C stocks occurred under the condition of removal of 20% of aboveground structures of mangrove trees, indicating the optimal removal area for mangrove management in the Danshuei River. This study provides a case study exhibiting the tradeoffs between ecosystem services in mangrove management.