Ecosystem Carbon Stocks of Micronesian Mangrove Forests

Among the least studied ecosystem services of mangroves is their value as global carbon (C) stocks. This is significant as mangroves are subject to rapid rates of deforestation and therefore could be significant sources of atmospheric emissions. Mangroves could be key ecosystems in strategies addressing the mitigation of climate change though reduced deforestation. We quantified ecosystem C stocks at the seaward, interior, and upland edges of mangroves in the Republic of Palau and Yap, Federated States of Micronesia. The relatively high aboveground biomass coupled with carbon-rich soils resulted in the presence of large ecosystem carbon stocks compared to other tropical forests. Ecosystem C storage at the Palau site ranged from 479 Mg/ha in the seaward zone to 1,068 Mg/ha in the landward zone; in the Yap site C storage ranged from 853 to 1,385 Mg/ha along this gradient. Soils contained ~70% of the ecosystem C stocks. The elevation range of mangroves was <146 cm, suggesting that projected sea-level rise can influence a large portion of existing stands. Declines in ecosystem carbon stocks will be pronounced if mangroves are replaced by communities adapted to greater inundation such as seagrass communities, where C pools were ≤7% of that of mangroves (48 Mg C/ha).