Study Finds Early Signs of Widespread Coastal Marsh Decline

June 24, 2025 • by Jayme DeLoss

The early warning could help the ecosystems that are key to preventing flooding, UT marine science researchers say.

The sun rises over a marsh with a lot of greenery in the foreground and trees in the distance.

The sun rises over a salt marsh on Sapelo Island, Georgia, in February 2023. Marshes protect the coast from storm surge flooding and sea-level rise. Photo by Kyle Runion.


“Our findings show widespread belowground decline over the past decade and suggest this is an early warning sign of marsh deterioration and loss,” said lead author Kyle Runion, a research scientist at the University of Georgia who was at UT Austin’s Marine Science Institute during the study. “By pinpointing where belowground loss is happening, we can get a head start on conservation and restoration projects to more effectively prevent marsh loss.”

Coastal marshes filter water, store carbon, act as habitat for wildlife and provide food and fishing livelihoods for people. Marshes also absorb storm surges and sea-level rise, preventing worse flooding inland.

“These marsh areas might be in someone’s backyard,” said senior author Jessica O’Connell, a Colorado State professor and Runion’s adviser. “It’s important to have this early warning and a chance to do something before you lose these special landscapes that people have an economic or emotional connection to.”

O’Connell added, “Conserving the natural landscape is a lot cheaper than losing it and then trying to come up with an environmentally engineered way to do the things that the land used to do.”

The study focused on the marsh grass Spartina alterniflora, which is found along much of the U.S. coast. The researchers examined the entire Georgia coast – an area for which they had extensive field data – and found belowground biomass has declined across 72% of Georgia’s coastal marsh since 2014, with nearly 30% suffering substantial loss.

They are now working to make the model universally applicable to all marsh plants and coastlines.

Coastal marshes develop extensive root networks, which expand the soils with organic-rich material and store 'blue carbon.' Photo by Kyle Runion

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