Blue Carbon Loss
Studies have shown that seagrass beds and ecosystems store as much if not more carbon than land based forests. Seagrass ecosystems store carbon faster, longer, and more than twice the amount of what terrestrial forests can store. The carbon stock stored in coastal vegetations like mangroves, sea grass beds, and tidal marshes are known as ‘blue carbon’.
But if coastal vegetation stores a significant part of global carbon emissions with such efficiency, it could also release that much carbon when disturbed.
According to the research article Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems published in PLos ONE, what amounts to an equivalent of between 3 to 19% of carbon released by deforestation is being released by coastal habitats undergoing conversion or habitat destruction. The numbers are significant even though the research team made their calculations to err on the conservative side. Linwood Peddleton and other scientists and researchers involved in the research say that this results in economic damages between $6 and $ 42 billion per year.
Blue carbon is stored in areas with coastal vegetation like mangroves, seagrass beds, and tidal/salt marshes. Disturbances from human activities are a major cause of blue carbon being released according to Daniel Donato of the University of Wisconsin, Madison, a co-author in the research article, reports Climate Central.
These coastal vegetation areas and ecosystems are being converted for coastal development and construction. Donato compares this to natural disturbances such as hurricanes that ecosystems have evolved to recover from, and says that recovery from construction and coastal development is much more difficult. The research article equates ‘conversion’ of these vegetated coastal ecosystems with ‘habitat destruction’. Some of these conversions are:
- offshore dredging
- urban development
- eutrophication of overlying waters
- forest over-exploitation
- construction of river dams
- aquacultures and rice paddies
- conversion to open water due to sea level rise and subsidence
Though vegetated coastal ecosystems have been lost in past centuries due to land-use, the research article states that this has accelerated in past decades. The team calculates a loss of 30-40% of tidal marshes and seagrasses, and almost 100% of mangroves in the next 100 years depending on current conversion rates.
What has accumulated over centuries and millennia is now in danger of being released in a matter of decades. With the destruction of these vegetated coastal ecosystems, carbon sequestration potential as well as significant ecosystem services are lost along with blue carbon stocks. The research article mentions that at present, blue carbon emissions are given little attention compared to land based sources in either emissions accounting or carbon market protocols. Policies pushing for sustainable management of these coastal ecosystems might prove crucial in reducing carbon emissions from the land-use sector as well as in the preservation of key coastal ecosystem services.
Research Article Source: Pendleton L, Donato DC, Murray BC, Crooks S, Jenkins WA, et al. (2012) Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems. PLoS ONE 7(9): e43542. doi:10.1371/journal.pone.0043542
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