Assessing blue carbon in mangrove ecosystems of Seychelles

Mangrove forests play an important role in climate change mitigation and adaptation, globally recognized as natural climate solution. The protection and restoration of mangrove ecosystems are especially important to Small Island Developing States, like Seychelles, due to their vulnerability to the impacts of climate change, such as sea level rise and tropical cyclones. Therefore, it is crucial for countries like Seychelles to develop baseline information on the status of their mangrove forests to guide conservation and management actions. In this study, we conducted a field campaign to collect local data on plant (i.e., aboveground and belowground) and soil carbon from representative mangrove forests in the inner and outer islands of Seychelles. We used this data to develop, for the first time, a blue carbon assessment for Seychelles' mangrove ecosystems. Seychelles holds 2195 ha of mangrove forests, with ∼80% of them found on the outer island of Aldabra Atoll. Seychelles mangrove ecosystems store 688,091 ± 18,353 tonnes of organic carbon (or 2.5 million tonnes CO₂e) and an average of 477.0 ± 16.2 tonnes of carbon per hectare, with 70% of their total carbon stocks stored in their soils. Aldabra Atoll holds the highest total carbon stocks, accounting for 67% of Seychelles' mangrove stocks, despite having a relatively shallow soil organic layer (∼40 cm) due to the dominance of limestone and 'coral champignon' below 40 cm depth. Seychelles currently protects ∼85% of its mangrove extent including the Aldabra Atoll, a UNESCO World Heritage and Ramsar site, and Port Launay, a Ramsar site. Overall, field data from this study demonstrates the important climate mitigation potential of Seychelles' mangrove forests and the important role they play in supporting Seychelles in achieving its Nationally Determined Contributions (NDCs) commitments.