Impacts of Climate Change on Blue Carbon Stocks and Fluxes in Mangrove Forests: Fid-Bau Portal

Impacts of Climate Change on Blue Carbon Stocks and Fluxes in Mangrove Forests

Daniel Michael Alongi

Mangroves store blue carbon (693 Mg C_ORG ha⁻¹) disproportionate to their small area, mainly (74%) in deep soil horizons. Global stock estimates for mangroves (5.23–8.63 Pg C_ORG) are equivalent to 15–24% of those in the tropical coastal ocean. Carbon burial in mangrove soils averages 184 g C_ORG m⁻² a⁻¹ with global estimates (9.6–15.8 Tg C_ORG a⁻¹) reflecting their importance in carbon sequestration. Extreme weather events result in carbon stock losses and declines in carbon cycling and export. Increased frequency and ferocity of storms result in increasingly negative responses with increasing strength. Increasing temperatures result in increases in carbon stocks and cycling up to a critical threshold, while positive/negative responses will likely result from increases/decreases in rainfall. Forest responses to sea-level rise (SLR) and rising CO₂ are species- and site-specific and complex due to interactive effects with other drivers (e.g., temperature, salinity). The SLR critical threshold is ≈ 6 mm a⁻¹ indicating survival only under very low-low CO₂ emissions scenarios. Under low coastal squeeze, landward migration could result in sequestration and CO₂ losses of 1.5 and −1.1 Pg C with net stock gains and losses (−0.3 to +0.5 Pg C) and CO₂ losses (−3.4 Pg) under high coastal squeeze.