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SOURCE: Mongabay

DATE: July 13, 2018

SNIP: Mangroves, the dense tangled forests that buffer land from sea in many coastal areas of the tropics, are renowned for their ability to store carbon and help fight climate change. But new research finds mangroves may emit more carbon as methane than previously estimated – emissions made even worse by deforestation.

The ability of mangroves to sequester carbon in the ground – termed “blue carbon” – is unparalleled, with previous research finding a tract of mangrove can bury 40 times more carbon than a similarly sized area of rainforest.

Their results, published in Science Advances, reveal that mangrove soil carbon doesn’t remain stored in perpetuity. Some of it is transformed from carbon dioxide (CO2) to methane (CH4) by tiny microorganisims called archea, and is then released back into the atmosphere. Methane has a much bigger warming impact than carbon dioxide – 34 to 86 times more powerful – so even a bit of methane has the potential to offset mangrove CO2 storage.

Ultimately, the team found that the methane released from mangrove soil carbon offsets blue carbon burial rates by an average of 20 percent. They say their results show that methane emissions should be factored into carbon accounting when evaluating the carbon storage potential of mangrove forests.

The researchers say that deforestation has the potential to increase these emissions. Mangroves around the world are being deforested at a fast clip, with between 30 and 50 percent lost over the past half-century to agriculture, aquaculture and infrastructure development.