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.
The rate of loss of these marine ecosystems is much higher than any other ecosystem on the planet – in some instances up to four times that of rainforests. Currently, on average, between 2–7% of our blue carbon sinks are lost annually, a seven-fold increase compared to only half a century ago. If more action is not taken to sustain these vital ecosystems, most may be lost within two decades. Halting degradation and restoring both the lost marine carbon sinks in the oceans and slowing deforestation of the tropical forests on land could result in mitigating emissions by up to 25%.
Sustaining blue carbon sinks will be crucial for ecosystem-based adaptation strategies that reduce vulnerability of human coastal communities to climate change. Halting the decline of ocean and coastal ecosystems would also generate economic revenue, food security and improve livelihoods in the coastal zone. It would also provide major economic and development opportunities for coastal communities around the world…
“Out of all the biological carbon captured in the world, over half is captured by marine living organisms hence it is called blue carbon.”
“The objective of this report is to highlight the critical role of the oceans and ocean ecosystems in maintaining our climate and in assisting policy makers to mainstream an oceans agenda into national and international climate change initiatives.”
Read/download the entire report here: http://www.grida.no/publications/145