Mangrove forests play a key role in climate change mitigation and adaptation, globally recognised as ‘Natural Climate Solutions’ (NCS). However, they, along with other blue carbon ecosystems, have experienced worldwide decline due to pressures from human activity such as land-use change, pollution, and overexploitation. For these coastal ecosystems to meaningfully mitigate impacts of climate change we need to protect what mangrove forests we still have, as well as restoring forests that have been degraded or destroyed.
If you live on an island, climate change poses an existential risk. Sea level rise and tropical cyclones can have devastating impacts on countries like Seychelles and other Small Island Developing States. Seychelles’ Ministry of Agriculture, Climate Change and Environment (MACCE) aims to develop baseline information on the status of their mangrove carbon stores to guide current and future conservation and management actions and combat the risks of climate change.
On-ground estimates of Seychelles’ mangrove carbon stocks
Researchers from Deakin University’s Blue Carbon Lab led the ‘Blue Carbon Assessment for Mangrove Systems’ in Seychelles to collect and analyse local scale data on the carbon contained within the plants (aboveground and belowground) as well as within the soil of mangrove forests in the inner and outer islands of Seychelles. BCL researchers collaborated with local Seychellois consultant Dr Barry Nourice to provide expertise and training in preparation for Dr Nourice to lead the extensive fieldwork campaign.
“Our team, including 7 local fieldwork staff, visited 7 islands, including the inner islands of Mahé, Praslin, La Digue, Curieuse and Silhouette and outer islands of Aldabra Atoll and Cosmoledo Atoll. The field team worked tirelessly to sample 27 mangrove forests sites across the islands, in total collecting 187 soil cores (1 metre) and 132 above-ground biomass surveys involving measurements from a staggering 1700+ individual trees. It was an incredible feat, and the insights we gained from this massive sampling effort will undoubtedly be invaluable in the ongoing efforts to better understand and protect these important coastal habitats,” Dr Nourice highlighted.
Seychelles’ mangrove forests are comprised of up to 8 different mangrove species and stretch 2,195 hectares across the inner and outer islands. 80% of all of Seychelles’ mangroves are found on the Aldabra Atoll alone.
Dr Nourice and his research team processed and analysed the mangrove soil samples via Loss on Ignition (LOI) in Seychelles at the Seychelles Agricultural Agency (SAA) Soil diagnostic laboratory. Scientists from Deakin’s Blue Carbon Lab then used the mangrove carbon data to develop for the first time a blue carbon assessment for mangrove ecosystems in Seychelles.
On-ground sampling revealed that Seychelles’ mangrove forests store approximately 688,091 tonnes of organic carbon, equivalent to ~2.5 million tonnes CO2e. This works out to be an average of 313.48 tonnes of carbon per hectare. Importantly, 70% of the total carbon is stored in the soil, locking it away for an exceptionally long time.
The current extent of total mangrove forests across Seychelles is sequestering 14,017 tonnes of CO2e annually, equivalent to ~3% of Seychelle’s annual CO2 emissions – making them a crucial tool in achieving Seychelles’ Nationally Determined Contributions commitments and highlighting the carbon capture prowess of blue carbon ecosystems.
“The good news is that Seychelles already protects about 84% of its current mangrove forests including those found on the Aldabra Atoll, a UNESCO World Heritage and Ramsar site, and Port Launay, a Ramsar site,” says Blue Carbon Lab’s Dr Melissa Wartman.
In September 2022, Dr Wartman, fellow Blue Carbon Lab researchers Dr Costa and Dr Palacios, and Dr Nourice delivered the results of the mangrove assessment through a half-day workshop. The workshop was opened by Minister for Agriculture, Climate Change and Environment, Mr Flavien Joubert (MACCE) and was attended by thirty participants from over 15 organisations including MACCE, Seychelles Islands Foundation (SIF), the University of Seychelles, Nature Seychelles, Marine Conservation Society Seychelles (MCSS), among others.
Where to next for Seychelles’ blue carbon science?
Scientists from Deakin’s Blue Carbon Lab made several recommendations on priority areas for continued advancement of mangrove research in Seychelles, including empowering local scientists and setting up a monitoring program to assess the risks of ecosystem degradation. Next steps for protecting Seychelles’ mangroves should include quantifying the ecosystem services provided by mangrove forests. As with many of our blue carbon ecosystems, valuing their ecological, social and economic benefits is key to supporting their protection and restoration, as well as for access to alternative financial markets (payments for ecosystem services).
“With so much potential mangroves have in mitigation of growing GHG levels, Seychelles continues to reaffirm its strong commitment towards the conservation of its blue carbon ecosystems. Due to the critical benefits arising from blue carbon ecosystems such as mangroves and seagrass, the Government of Seychelles, has committed to ensure that these ecosystems are considered in its decision making and aim to protect 100% of its mangroves and seagrass ecosystem by the end of this year,” says Minister Joubert.
The team compiled their research findings and recommendations in the report “Blue Carbon Assessment for mangrove systems in Seychelles” that has been accepted by the Seychelles’ Ministry of Agriculture, Climate Change and Environment. You can read and download the report in full here.