Restoring mangroves lost by aquaculture offers large blue carbon benefits

SCIENCE FOR SOCIETY Conservation and restoration of blue carbon ecosystems, such as mangrove forests, represent a vital nature-based solution for climate change mitigation. Historically, mangroves have experienced extensive deforestation due to human activities, particularly aquaculture. Deforested areas now offer opportunities for achieving mangrove restoration targets, as they may still possess suitable environmental conditions for mangrove growth. Evaluating the feasibility of mangrove restoration at a fine scale allows for the identification of priority areas, thereby guiding on-the-ground restoration efforts. Our study indicates that aquaculture ponds historically converted from mangroves remain largely suitable for mangrove restoration and hold the potential for substantial blue carbon benefits. These findings can better formulate cost-effective strategies for mangrove restoration, thereby mitigating climate change more efficiently. SUMMARY Mangrove forests show great potential for mitigating climate change due to their high carbon densities but have faced extensive deforestation due to aquaculture. Aquaculture areas offer opportunities for mangrove restoration, as most still maintain suitable landscape-scale biophysical conditions. Despite this potential, the scale and biophysical suitability of aquaculture areas for large-scale mangrove restoration, along with associated carbon benefits and costs, remain poorly understood. We assess the restoration suitability of mangroves deforested by aquaculture and identify patch-scale priority areas in China and southeast Asia. Long-term satellite observations show that aquaculture expansion has caused the loss of 165,079 ha of mangroves. Habitat suitability modeling estimates that 60% of these lost mangroves are biophysically feasible for restoration and potentially removing 84 (75-96, 95% confidence interval) Mt CO2. Our findings provide spatially explicit guidance for mangrove restoration planning and highlight the contribution that mangrove restoration can make to nationally determined contributions for climate change mitigation.