Oceans play a significant role in the global carbon cycle. Not only do they represent the largest long-term sink for carbon but they also store and redistribute CO2. Some 93% of the earth’s CO2 (40 Tt) is stored and cycled through the oceans.

The ocean’s vegetated habitats, in particular mangroves, salt marshes and seagrasses, cover <0.5% of the sea bed. These form earth’s blue carbon sinks and account for more than 50%, perhaps as much as 71%, of all carbon storage in ocean sediments. They comprise only 0.05% of the plant biomass on land, but store a comparable amount of carbon per year, and thus rank among the most intense carbon sinks on the planet. Blue carbon sinks and estuaries capture and store between 235–450 Tg C every year – or the equivalent of up to half of the emissions from the entire global transport sector, estimated at around 1,000 Tg C yr–1. By preventing the further loss and degradation of these ecosystems and catalyzing their recovery, we can contribute to offsetting 3–7% of current fossil fuel emissions (totaling 7,200 Tg C yr–1) in two decades – over half of that projected for reducing rainforest deforestation. The effect would be equivalent to at least 10% of the reductions needed to keep concentrations of CO2 in the atmosphere below 450 ppm. If managed properly, blue carbon sinks, therefore, have the potential to play an important role in mitigating climate change. Continue reading →