For 5,000 Years Mangroves In Mexico Have Been Storing Carbon

By D.C. Demetre •  Updated: 09/19/22 •  3 min read

Mangrove forests have been silently keeping carbon out of the Earth’s atmosphere for the past 5,000 years, according to researchers, who have discovered a new incentive to preserve them.

Mangroves can survive in environments that other plants cannot, such as salty coastal seas. When the tide is high, some species’ air-conducting, vertical roots function like snorkels, giving the impression that the trees are floating on stilts.

A research team led by the universities of California, Riverside and San Diego set out to explain the biogeochemical cycling that occurs in the maritime mangroves off the coast of La Paz, Mexico, as they take in and release components like nitrogen and carbon. The group was equally interested in finding out what bacteria and fungi are flourishing there because microorganisms are mostly responsible for these activities.

5000 Year Old Carbon

mangrove trees growing along the edge of a river storing carbon
The researchers anticipated finding carbon in the peat layer beneath the forest, but they did not anticipate finding carbon that was 5,000 years old.

“What’s special about these mangrove sites isn’t that they’re the fastest at carbon storage, but that they have kept the carbon for so long. It is orders of magnitude more carbon storage than most other ecosystems in the region,”

said senior co-author Emma Aronson, environmental microbiologist.

The peat is a mixture of submerged sediment and organic material that has partially decomposed beneath the mangrove trees. The peat layer in some of the study’s sampled sites stretched around 10 feet below the level of the coastal waters.

The team probably did not detect any fungi living in the lowest peat layer because little oxygen makes it there; typically, fungi are present in almost every ecosystem on Earth. However, the majority of fungi that specialise in dissolving carbon compounds need oxygen to survive. The group may investigate the lack of fungi in mangrove peat research in the future.

Bacteria Species That Break Down Carbon

More than 1,100 different bacterial species that consume and excrete different chemical substances can be found dwelling beneath mangroves. Many of them work in conditions with little or no oxygen. These bacteria are ineffective in decomposing carbon, though.

“The deeper you go into the peat soils, the fewer microorganisms you find. Not much can break down the carbon down there, or the peat itself, for that matter. Because it persists for so long, it’s not easy to make more of it or replicate the communities of microbes within it,”

said microbial ecologist and study author Mia Maltz.

On Earth, there are other ecosystems that have carbon that is at least as old as or even older. Examples include the Arctic and Antarctic permafrost regions, where the ice hasn’t yet thawed and allowed gases to escape. possibly additional mangrove forests. Currently, the scientists are also scouting mangrove research locations in Hawaii, Florida, and the Yucatan Peninsula of Mexico.

“These sites are protecting carbon that has been there for millennia. Disturbing them would cause a carbon emission that we wouldn’t be able to repair any time soon,”

said the paper’s first author Matthew Costa, UC San Diego coastal ecologist.

The greenhouse effect, which is warming the earth, is amplified by carbon dioxide. Mangroves should be left alone, according to Costa, in order to prevent this problem from getting worse.

“If we let these forests keep functioning, they can retain the carbon they’ve sequestered out of our atmosphere, essentially permanently. These mangroves have an important role in mitigating climate change,”

Costa said.

The study was published in the journal Marine Ecology Progress Series.