Glob. Biogeochem. Cycles 22, GB2013 (2008)
Over half of the carbon dioxide taken up by mangrove forests has been unaccounted for until now. Scientists show in a new study that this 'lost carbon' is probably washed away with the tide.
Steven Bouillon of the University of Brussels and colleagues scoured the available literature and came up with a global estimate for the amount and fate of carbon fixed during photosynthesis by mangrove vegetation. Although nearly half of the carbon appeared to be siphoned off into soils or released back into the atmosphere, the rest — averaging 112 million tonnes per year — could not be found. Because previous studies used the amount of carbon dioxide released from mangrove soils as a measure of soil carbon breakdown, they severely underestimated the rate at which carbon passes through mangrove ecosystems. Bouillon and colleagues conclude that the missing carbon may be leaving the mangroves for coastal waters.
Mangrove forests are disappearing fast, with the UN Food and Agriculture Organisation estimating global losses around one per cent of the total area per year. Their decline will shrink a vital land carbon sink and could also affect the amount of carbon being transported from coastal waters to the deep sea, where it is sequestered from the atmosphere.