LA PAZ, Sept 21 — Researchers have discovered that mangrove forests located in the Mexican city of La Paz have been storing carbon in their roots for several thousand years. This unsuspected potential in the mitigation of climate change makes the protection of these tropical forests more necessary than ever.

When you hear about carbon sinks and forests, you probably think of the Amazon, the Taiga or the Congo Rainforest. And you’d be right, since these are the largest forest complexes in the world. But, although much less in the limelight, the mangrove forests of Mexico also play an important role in terms of carbon sequestration. According to recent research published in the scientific journal Marine Ecology Progress Series, these forests have been quietly preventing carbon from entering the Earth’s atmosphere for as long as 5,000 years!

Mangroves are complexes of trees and plants that thrive at the edge of coastlines, mostly in regions with tropical climates. A research team led by professors at UC Riverside and UC San Diego (California, USA) sought to understand how marine mangroves off the coast of La Paz, Mexico, absorb and release natural gases such as nitrogen and carbon dioxide.

Since these processes are largely determined by microbes, the researchers studied the bacteria and fungi that grew on the plants. And while they expected to find carbon in the peat layer beneath the forest, they did not expect that carbon to be thousands of years old.

This is where the significance of such a discovery lies: “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,” said in a statement.

Valuable ecosystems in the fight against global warming

Mexican mangrove forests are not the only ecosystems on Earth known to have been holding carbon for several centuries. The Arctic permafrost is perhaps the most emblematic example. But, according to the authors of this work, it is possible that other mangroves have been doing the same. Researchers are currently scouting for other mangrove research sites, including in Hawaii, Florida and the Yucatan Peninsula (southeast 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. If we let these forests keep functioning, they can retain the carbon they’ve sequestered out of our atmosphere, essentially permanently,” said Matthew Costa, UC San Diego coastal ecologist and first author on the paper.

This is not the first time that research has drawn attention to the important role that ecosystems like mangroves can play in limiting global warming. Research published in May in the Science journal, and carried out by German, American and Dutch researchers, found that marsh plants, found in zones such as peat bogs, salt marshes, mangrove forests and seagrass beds, cover only 1 per cent of the Earth’s total surface, but they sequester more than 20 per cent of all the CO2 absorbed by ecosystems worldwide. — ETX Studio