A powerful climate solution just below the surface of the sea (2023)


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Restoration of salt marshes is a tool coastal communities can use to address climate change, both by sequestering emissions and mitigating their effects.

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A powerful climate solution just below the surface of the sea (1)

AfterTatiana Schlossberg

They can kiss coastlines, break wave forces, create habitats for fish, shellfish and migratory birds, clean water, store as much as 5 percent of the world's carbon dioxide and pump oxygen into the ocean, and in part create life on Earth as we know it. it's possible.

These amazing machines are not the latest great technological invention. Instead, they are one of nature's earliest floral creations: seagrasses. Anchored to the shores of every continent except Antarctica, these plants (and they are plants, not algae that sprout, bloom, fruit, and produce seeds) are one of the most powerful, yet unspoken climate solutions already on the planet .

Seagrass restoration is one of the tools coastal communities can use to tackle climate change, both by sequestering emissions and mitigating their effects, which is one of the topics discussed as leaders in business, science, culture and politics gather on Thursday and Friday in Busan, South Korea, forNew York Times konference, The New Climate.

Around the world, scientists, NGOs and volunteers are working to restore salt marshes, if not to their original glory, then to something far more spacious and magnificent than the barren, muddy bottom left after damage or destruction.


Seagrass meadows are making a comeback in places like Virginia, parts of the UK and Western Australia with the help of dedicated researchers and citizen scientists. They bring with them cleaner water, more stable coasts, and animals and other organisms that once lived there. And yet seaweed doesn't get the attention it deserves, say its supporters.

It's impossible to know exactly how much seaweed has been lost because scientists don't know how much there was to begin with.

Only about 16 percent of global coastal ecosystems are considered intact, and seagrasses are among the hardest hit. An estimated one-third of seagrass globally has disappeared in the past few decades, according toMatthew Long, research assistant in marine chemistry and geochemistry at Woods Hole Oceanographic Institution. "Globally, a football field of seagrass is lost every 30 minutes," said Dr. Long, "and we're losing about 5 to 10 percent every year at an accelerating rate."

"Sugargrass is adversely affected by global stressors:deoxygenering, ocean acidification and warming temperatures,” said Dr. Long. But local stressors have also played a role in their demise, mainly in the form of nutrient pollution, mainly from agricultural runoff and sewage, and subsequent algal blooms and die-offs, which first suffocate other plants such as seagrasses (a process called eutrophication) and then take over by decomposition of all the oxygen in the water (hypoxia).


Although the effects of climate change and increasing human impacts have accelerated the loss of seagrass in recent decades, it is not a new story.

On Virginia's eastern shore, a severe storm in August 1933, following a debilitating disease and overharvesting of scallops, wiped out what remained of once large eelgrass beds. (Eelgrass is a type of seagrass.) For decades, there was no eelgrass on the seaward side of the coast, said Bo Lusk, a scientist withInstitute for Nature Conservation Volgenau Virginia Coast Reserve, although some remained on the part of the coast washed by the Chesapeake Bay.

Dr. Lusk, who grew up in the region, heard stories of lush green carpets of eelgrass from his grandmother as a child, remembering the shores teeming with life — until they weren't. But then, in 1997, someone reported seeing some patches of eelgrass on the seashore, possibly from seeds that accidentally came south from Maryland and settled in a welcoming neighborhood in Virginia.

After several years of experiments, Robert J. Orth, a scientist atVirginia Institute of Marine Science, devised a highly successful seagrass restoration method that is similar to methods used around the world: In the spring, scientists and hundreds of volunteers collect seeds, which they count and process over the summer, and plant in the sediment in the fall.

Since 2003, when the restoration began inVolgenau Virginia Coast Reservebegan, researchers and others planted about 600 hectares of seeds, and the seagrass now covers 10,000 hectares, according to Dr. Lusk. Later this year, the Nature Conservancy hopes to sell the first confirmed blue carbon credits for seagrass based on this restoration effort, said Jill Bieri, director of the conservancy.

However, the success of the Virginia project has been somewhat difficult to replicate around the world. "You can't do that anywhere," said Dr. Lusk. "If the Nature Conservancy hadn't started this work of protecting the land 50 years ago, buying up parts of the coast to preserve it, there's a good chance we wouldn't have the water quality we have now, and it wouldn't be equally successful.”

Restoring seagrasses will take decades of commitment, said Dr. Lusk. Richard Unsworth, Associate Professor of Life Sciences at Swansea University in Wales and Founder and Chief Scientific OfficerSeagrass project, a British non-governmental organization working on seagrass restoration, said an important part of the work is making a long-term commitment to the whole ecosystem - to the salt marshes, but also to the people in the community.

"Fishermen's actions, boat owners' attitudes, water quality issues - all of these can be part of a complex socio-cultural situation and in the long run will be incredibly successful, but it's a slow process, not a silver bullet where you plant something , and then you saved it," said Dr. Unsworth.


Community engagement has been a necessary part of seagrass' success, as it takes a lot of work to collect and plant millions of seeds. For Project Seagrass, this also meant developing a website and an app,Seagrass watcher, which allows users to upload images of seagrasses in the wild (which are then verified by scientists), to help researchers fully map the extent and species of seagrasses worldwide, as seagrass mapping on a global scale is quite patchy.

But one place that has been well mapped is Shark Bay, a remote stretch of coast in Western Australia where it was discovered that 10 different salt marshes are actuallyonly one plant, probably the largest in the world.

There, seagrass has been growing and accumulating carbon in its plant material, but also in the sediment, for more than 3,000 years, he said.Elizabeth Sinclair, an evolutionary biologist from the University of Western Australia.

But during the extreme marine heat wave of 2010-2011, about a third of the seagrass canopy (what is visible above the sand) died and even releasednine million tonnes of carbonaccording to an estimate.

Over the past decade or so, Dr. Sinclair and her colleagues studied seagrass recovery - places where it has returned naturally and where it probably never will without the help of scientists as well as the Malgans, indigenous Australians who work as rangers.

Despite rising temperatures and changes in ocean chemistry making full restoration impossible, it's still work worth doing, said Dr. Lusk, whether it's the winding waterways of the Virginia coast, the rocky shores of Wales or the wide, endless bays of Western Australia.

"There are so many logical reasons why we should do this," said Dr. Lusk. “Carbon storage is great, coastal protection, all these other things are great and you can know it in your head, but until you get in the water and actually spend some time inside this system, you don't have an emotional connection.

"I would continue to do this if there was no carbon storage. It just feels good to be there."

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