Variability in blue carbon stocks across mangrove forest types in Jamaica

Abstract

Mangroves are among the most carbon-rich tropical forests, with much of their carbon stock located in underlying sediments. They play a vital role in climate mitigation and adaptation by offsetting carbon dioxide emissions linked to global warming. Despite their importance, blue carbon ecosystems remain poorly represented in climate policy across the Caribbean, with Jamaica and Belize being the only Caribbean countries to incorporate blue carbon stock values into their Nationally Determined Contributions (NDCs). Limited standardized information on mangrove carbon stocks across representative forest types in the region, further constrains the development of national baselines and their integration into climate policies. We conducted comprehensive mangrove carbon assessments across seven sites within four forest ecotypes: riverine, fringing, cay and lake to establish a national carbon baseline. The national mean total ecosystem carbon stock was determined to be 387.8 ± 18.6 Mg C ha -1 . Recent island-wide mapping of mangrove forests determined Jamaica’s total mangrove extent to be 11,978 ha. Using these values, a total national carbon stock of 4.7 ± 0.2 Tg C was determined for Jamaican mangrove forests, with 3.5 Tg C stored as sediment stocks, 1.1 Tg C as above and below-ground tree biomass and 0.08 Tg C as standing dead tree biomass. Results indicate that forests within freshwater systems had the greatest carbon stored as living biomass (79.5 ± 15.7 Mg C ha -1 ), while forests on small mangrove cays, had the highest sediment carbon (344.6 ± 13.1 Mg C ha -1 ) despite influences from tidal flows. The random forest regression predictor identified sediment pH as important predictors across all carbon components, while forest type was important for standing dead and sediment carbon. Water salinity was a strong predictor of standing dead carbon and a weak and negative predictor for biomass carbon. This study provides valuable insight on the variability of mangrove carbon in different forest types potentially supporting sustainable management and conservation strategies necessary to inform policy. It represents the most extensive mangrove carbon assessment done in Jamaica with results informing the 2025 update of the island’s NDCs, a commitment under the Paris Agreement.