The Wetlands Are Drowning | WIRED


Schoenoplectus americanus, or chair shark, is a wetland plant common in the Americas, and has an existential problem. He has chosen to live in a place where he always runs the risk of drowning.

Like all plants, garbage needs oxygen to produce energy. One solution is obvious: send shoots to the sky like straws to suck oxygen to the roots. But the rush also employs a more unusual strategy: raising the ground where it grows. The plant builds its roots near the surface, where they trap sediments and organic mud flowing into the swamp. Eventually, the entire ecosystem rises a little higher, and the reed is not drowned.

“We often call them ecosystem engineers,” says Pat Megonigal, an ecologist who leads the Smithsonian’s global change research wetland and studies plants. “If the water goes deep, they have the ability to rise. And in fact, right here in this swamp they do it for 4,000 years.”

Wetland researchers have long wondered if this ability could help plants cope with climate change. As sea levels rise, causing more severe and frequent storm surges, the risk of plants drowning also increases. But rising levels of carbon dioxide in the atmosphere are also a great help to the plant’s basement construction project, providing more fuel for photosynthesis and helping them build larger roots. For 30 years, Megonigal and his predecessors have been watching this marathon run in a single Maryland swamp in Chesapeake Bay. It is a duel between the rising sea and the growth of plants, two forces with a common origin: humans burn fossil fuels, adding more CO2 in the air — and at this point the result is obvious: the wetlands are losing.

These findings, which were published last week in Advances in Science, they are diverting some of the most optimistic assumptions about how coastal areas might adapt to rising seas. Wetlands are important ecosystems in their own right and mediate the flow of nutrients between land and sea. They also puncture above its weight in terms of carbon storage, packing it into dense peat soils at concentrations that exceed those found in tropical forests. But the fate of these areas is uncertain in the face of climate change. At the turn of the century, estimates suggest that climate-induced changes could result in the loss of 20 to 50 percent of these ecosystems. The ability of wetlands to rise above rising waters is a key factor in determining whether they can persist where they are or whether they will have to migrate inland.

“Wow. We have always thought that high CO2 It would help stabilize the swamps, and this work really challenges that idea, “said Matthew Kirwan, an ecologist at the Virginia Institute of Marine Science, who studies how coastal landscapes evolve. they fundamentally change the way we understand swamp ecosystems. “

The experimental chambers of the Smithsonian Environmental Research Center in Edgewater, Maryland. Photo by Tom Mozdzer

Photography: Tom Mozdzer



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