Researchers have discovered a new incentive to safeguard mangrove forests: for the past 5,000 years, they have been silently removing carbon from the Earth's atmosphere.
Mangroves flourish in circumstances that most plants cannot, such as salty coastal seas.
When the tides are high, certain species have air-conducting, vertical roots that behave like snorkels, creating the impression of trees floating on stilts.
A study team led by UC Riverside and UC San Diego set out to discover how maritime mangroves off the coast of La Paz, Mexico, collected and released components, such as nitrogen and carbon, a process known as biogeochemical cycling.
Mexican mangroves have been capturing carbon for 5,000 years
Because these processes are mostly controlled by microorganisms, the team was particularly interested in learning which bacteria and fungi thrive there, as per ScienceDaily.
The scientists anticipated finding carbon in a layer of peat beneath the forest, but they did not expect it to be 5,000 years old.
This finding, as well as a description of the bacteria discovered, has been published in the journal Marine Ecology Progress Series.
What makes these mangrove locations unique is that they have held the carbon for so long, according to Emma Aronson, a UCR environmental microbiologist and senior co-author of the study.
It has orders of magnitude greater carbon storage than the majority of the region's other ecosystems.
The peat beneath the mangrove plants is made up of submerged silt and partially degraded organic materials and is stretched approximately 10 feet below the coastal sea line in certain sites examined for this study.
Little oxygen reaches the lowest peat layer, which is likely why the scientists detected no fungus alive in there; fungi are generally present in practically every ecosystem on Earth.
However, most fungi that specialize in the breakdown of carbon compounds require oxygen.
In future mangrove peat research, scientists may look into the lack of fungus further.
More than 1,100 different species of bacteria live beneath the mangroves, consuming and excreting a wide range of chemical components.
The fewer microorganisms you find in peat soils, the deeper you go.
Not much can break the carbon down there, or the peat itself, for that matter," said Mia Maltz, a UCR microbial ecologist, and research author. "Because it lasts so long, it's difficult to manufacture more of it or replicate the communities of microorganisms that live inside it."
Other ecosystems on Earth are known to have similarly aged or even older carbon, such as Arctic or Antarctic permafrost, where the ice hasn't yet thawed, allowing gas release, and potentially other mangrove forests.
The researchers are now scouting mangrove research sites in Hawaii, Florida, and Mexico's Yucatan Peninsula.
These locations are preserving carbon that has been there for millennia.
Disturbing them would result in carbon emissions that we would be unable to fix anytime soon, according to Matthew Costa, a UC San Diego marine ecologist and the paper's first author.
Carbon dioxide contributes to the greenhouse effect, which causes the globe to warm.
Costa argued that leaving mangroves alone is one approach to prevent this problem from escalating.
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Why Mangroves Matter
Mangrove forests were traditionally thought to be marshy wastelands.
Planners, biologists, and coastal residents have all come to recognize them as the incredibly diverse and essential ecosystems that they are, as per the American Museum of Natural History
Mangroves, seagrass beds, and coral reefs all work together to maintain coastal zones healthy.
Thousands of species rely on mangroves for survival.
They also help to maintain shorelines, reducing erosion and preserving the land - and the people who live on it - from storms and waves.
Mangroves, seagrass meadows, and coral reefs are frequently found together and collaborate. The trees collect sediment and pollutants that would otherwise be washed into the sea.
Seagrass beds act as an additional barrier to silt and sludge that may suffocate the reefs.
Mangroves provide perfect breeding sites for a large proportion of the world's fish, shrimp, crabs, and other shellfish.
Many fish species, including barracuda, tarpon, and snook, seek refuge among the mangrove roots as youngsters, then migrate out to graze in the seagrass meadows as adults.
An estimated 75% of commercially harvested fish spend time in mangroves or rely on food webs traceable back to these coastal forests.
From bacteria to barnacles to Bengal tigers, mangrove forests provide a home for hundreds of species at all levels of the marine and forest food webs.
The trees provide habitat for bug species, enticing birds that seek refuge in the dense branches.
Hundreds of shorebird and migratory bird species, including kingfishers, herons, and egrets, use these coastal woodlands as breeding and resting grounds.
Crab-eating macaques, fisher cats, and gigantic monitor lizards prowl in the mangroves, as do endangered species like olive Ridley turtles, white-breasted sea eagles, tree climbing fish, proboscis monkeys, and dugongs.
And the soft soil beneath mangrove roots allows burrowing animals like snails and clams to hide. Other species feed in the fertile mud, such as crabs and shrimp.
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