Blue Carbon – Good News from the Ocean
How surprising would it be if you suddenly discovered there were gardens so fertile they could fix carbon from the atmosphere 50 times more efficiently than the lushest, fastest-growing tropical forest on Earth? How about if those gardens were large enough to stash away more carbon every year than all the plants on Earth, and do it securely for thousands of years? Would it feel like good news? It does to me.
This astonishing scenario has recently been validated in two important studies by the United Nations Environment Programme and the International Union for Conservation of Nature. The magical gardens are the mangrove swamps, salt marshes and eelgrass beds of the shallow coastal oceans, spreading across tropical and temperate latitudes. BC has an important share with our salt marshes and seagrass beds (we don't have mangroves).
Why are these ecoystems so efficient at storing carbon? The phenomenon is due to the uninterrupted sedimentation and burial of organic debris, the formation of deep roots by the standing plants and the primary production of microflora such as bacteria, algae, and diatoms which add carbon compounds continuously to the sediment.
Long-treasured for their services as nurseries for fish and invertebrates, marine bird and mammal feeding grounds and habitat for shellfish, we now have added reason to care for, preserve and restore these ecosystems, which cover a mere 0.5% of the ocean floor. They have not done so well lately, with roughly 30% of each habitat lost since the 1940’s and between 2 and 7% lost annually even now.
The compelling context of course is the pressing need not only to reduce our carbon emissions, but to find safe storage for a large proportion of those already in the air and water. It is a larger discussion to address how this might be done in total, but one thing is certain: if we are going to moderate global warming we need places to store carbon. Any reservoirs capable of sequestering carbon for long periods are priceless assets. These natural coastal carbon sinks take between 0.25 and 0.5 billion tonnes of carbon out of circulation every year – and we put approximately 10 billion tonnes into circulation! Solving between 2.5 and 5% of the problem is a blessing not to be ignored.
Have a look at this blue carbon math: in BC we have approximately 750 km2 of salt marsh and 335 km2 of seagrass meadows. Using global average carbon accumulation numbers for these ecosystems we can calculate the fixation of approximately 185,000 tonnes of carbon every year. BC’s 100,000 km2 of boreal forest sequesters 80-220,000 tonnes of carbon per year, which is roughly similar, but the area of the boreal forest is approximately 90 times that of the blue carbon habitats. In fact blue carbon sequestration in BC balances the emissions of slightly more than 200,000 passenger cars!
Our forests have blessed BC with vast carbon sequestration capacity, but highest on the cost-effectiveness scale are our salt marshes and eelgrass beds. It could be argued, in view of their manifold benefits, they occupy the highest possible priority for conservation, management and restoration.
