US Coastal Wetlands Risk Submerging as Sea Levels Rise, Study Finds

A nationwide study tracking nearly 450 coastal wetlands for up to two decades reveals that 84% of these ecosystems are gradually submerging and risking transformation into open water. Researchers found that only 16% are building elevation fast enough to outpace rising sea levels, posing severe threats to coastal flood protection and wildlife habitats.

Coastal wetlands across the contiguous United States are losing ground in a quiet race against rising seas. While scientists have long understood that climate change is accelerating sea-level rise, a new nationwide assessment has now measured how that race is going. Across the contiguous coasts, 84 percent of these valuable ecosystems are gradually inundating, putting them on a trajectory to become open water if current environmental trends continue.

The findings carry major implications for public safety and the economy. Coastal wetlands serve as natural buffers that absorb storm energy, protect roads and buildings, and offer critical habitats for migratory birds, fish, and endangered species. Because these ecosystems provide trillions of dollars in protective and ecological services every year, their gradual disappearance threatens both human infrastructure and biodiversity.

Tracking Elevation Across Four Hundred Fifty Monitoring Stations

Conducting long-term fieldwork in muddy, remote terrain requires specialized equipment, with some monitoring sites accessible only by boat or helicopter. To overcome these logistical hurdles and establish a national picture, researchers used elevation data from nearly 450 monitoring stations along the Atlantic, Gulf, and Pacific coasts. The team compared those elevation measurements with tide-gauge data collected over periods lasting up to 20 years.

The analysis revealed a nuanced picture of sediment dynamics. While 89 percent of coastal wetlands are gaining some elevation through sediment buildup, only 16 percent are doing so fast enough to outpace sea-level rise. The rest are falling behind, slowly sinking into a future where tides overtake them with increasing frequency.

Why the Gulf Coast Faces the Severest Vulnerability

The study highlights sharp regional disparities in wetland resilience. The Gulf Coast emerges as the most vulnerable region in the country, weighed down by a combination of accelerated sea-level rise and heavy human pressures. Historical shipping canals have altered natural waterways, starving wetlands of the river sediments required to sustain them. Additionally, oil and gas extraction has reduced underground pressure, causing the land above to subside literally.

By contrast, Atlantic Coast wetlands are generally holding up better. Submergence is slow enough at approximately 75 percent of Atlantic monitoring stations to rule out any critical threat of immediate submergence. Researchers attribute this relative stability partly to higher rates of marine sediment deposition delivered by ocean waves.

Global sea-level rise averaged 1.7 millimeters per year during the 20th century but accelerated in recent decades, hitting 3.8 millimeters per year from 2006 to 2018. While moderate water level increases can stimulate plant growth up to a point, excessive flooding shuts down biological systems entirely.

As flooding intensifies, plants decrease production and eventually die off, accelerating the loss of surface elevation.

Perspectives from Duke University and the U.S. Geological Survey

Justine Neville, a wetland ecologist at Duke University and lead author on the study published in Earth’s Future, noted that the regional results aligned closely with broader scientific literature. A lot of the literature that we’ve read from all the different regions is showing similar results, Neville explained, adding that she was not very surprised by the widespread submergence trend.

Emphasizing the ecological stakes, Neville noted that numerous endemic species, endangered wildlife, and migratory birds rely entirely on these coastal zones. There’s a whole host of benefits to culture, to flora and fauna, and economically speaking, so it is really important that we understand how [wetlands] are changing, she stated.

Inland Migration Corridors as a Path Forward

Despite the sobering statistics, the research indicates that coastal wetlands are not entirely trapped in place. The study found that 73 percent of the surveyed wetlands still retain an opportunity to move inland, provided the land behind them remains low enough and free from barriers like roads, levees, and urban development.

Conservation strategies will likely depend on protecting these migration corridors, restoring natural sediment flows, and removing dikes where feasible. Land managers face daunting logistics in muddy terrain, but the newly published data offers a roadmap for prioritizing where conservation and managed retreat efforts can preserve coastal resilience before rising tides permanently claim the marsh surface.

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