An acre per acre, a salt marsh like the one at the mouth of the West Scheldt in the Netherlands, stores five times more carbon than the forest. Credit: Edwin Money
Wetlands are the most effective natural system for storing global warming carbon dioxide.
Human activities such as draining swamps for agriculture and logging are increasingly eating away at salt and freshwater wetlands. These vital areas cover only 1% of the Earth’s surface, but store more than 20% of all global warming carbon dioxide absorbed by ecosystems around the world.
A new study published on May 6, 2022 in the journal Science by a team of Dutch, American and German scientists shows that it is not too late to reverse the losses.
The key to success, according to the authors, is the use of innovative restoration practices identified in the new research paper, which reproduce the natural processes of landscape construction and improve the carbon storage potential of restored wetlands.
And it does it on a huge scale.
“About 1% of the world’s wetlands are lost each year due to pollution or drying of wetlands for agriculture, development and other human activities,” said Brian R. Siliman, a respected professor of marine biology at Duke Brian University. Siliman, Rachel Carson. author of the study.
“Once disturbed, these wetlands emit huge amounts of CO2 from their soils, representing about 5 percent of global CO2 emissions per year,” Siliman said. “Hundreds, even thousands of years of stored carbon have been exposed to air and are rapidly decomposing and releasing greenhouse gases. The result is an invisible reverse waterfall of CO2 leaking into the atmosphere. Wetlands are shifting from carbon sinks to sources. “
“The good news is that we now know how to rehabilitate these wetlands on a scale never before possible, and in a way that both stops the release of carbon and restores the wetland’s storage capacity,” he said.
What makes most wetlands so efficient at storing carbon is that they are formed and held together by plants that grow close together, Siliman explained. Their dense above-ground and underground root and root substrates capture nutrient-rich residues and protect the soil from erosion or drying – all of which help plants grow better and the soil layer accumulate, locking much more CO2 into the process.
In the case of raised peat bogs, the process works a little differently, Siliman said. The layers of living peat moss on the surface act like mushrooms, retaining huge amounts of rainwater, which maintains its own growth and keeps a much thicker layer of dead peat moss beneath it permanently under water. This protects the lower layer of peat, which can be up to 10 meters thick, from drying out, decomposing and releasing the accumulated carbon back into the atmosphere. As live moss gradually accumulates, the amount of carbon stored underground is constantly increasing.
Successful restorations must repeat those processes, he said.
“More than half of all wetland restorations fail because the landscape-forming properties of plants are insufficiently taken into account,” said study co-author Tisse van der Heide of the Royal Institute of Marine Research and the University of Groningen in the Netherlands. Planting seedlings and corks in rows at equal distances from each other may seem logical, but it is counterproductive, he said.
“Restoration is much more successful when plants are placed in large dense piles, when their landscape-forming properties are mimicked, or simply when very large areas are restored at once,” van der Heide said.
“Following this guide will allow us to rebuild lost wetlands on a much larger scale and increase their chances of thriving and continuing to store carbon and provide other vital ecosystem services for years to come,” Siliman said. “Plants win, the planet wins, we all win.”
Siliman and van der Heide conducted the new study with scientists from the Dutch Royal Institute of Marine Research, the University of Utrecht, Radbud University, the University of Groningen, the University of Florida, the University of Duke and the University of Greifswald.
By synthesizing carbon capture data from recent research, they have found that the oceans and forests contain the most CO2 in the world, followed by wetlands.
“But when we looked at the amount of CO2 stored per square meter, it turned out that wetlands stored about five times more CO2 than forests and up to 500 times more than oceans,” said Ralph Temminck, a researcher at the University of Utrecht who co-authored the paper. the study.
Reference: “Restoring Biogeomorphic Wetlands Feedback to Restore the World’s Biotic Carbon Hotspots” by Ralph JM Temmink, Leon PM Lamers, Christine Angelini, Tjeerd J. Bouma, Christian Fritz, Johan van de Koppel, Robin Lexmond, Max Rietkerk, Brian R. Silliman, Hans Yosten and Tisse van der Heide, 6 May 2022, Science.DOI: 10.1126 / science.abn1479
Funding for the new study came from the Dutch Research Council, the Oak Foundation, Duke RESTORE, the Lenfest Ocean program, the National Science Foundation and the Natuurmonumenten.
In addition to his appointment as a teacher at Duke’s Nicholas School, Siliman is the director of Duke RESTORE.
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