84% of US coastal wetlands sinking as seas rise, study finds

America's coastal wetlands are losing a quiet, grinding battle against the sea. A new study tracking nearly 450 wetlands across the country's three coasts for up to two decades has found that 84% are slowly sinking toward open water. Only 16% are building up enough sediment and organic matter to keep pace with rising seas.

The findings, reported by Earth.com and picked up by outlets including Phys.org and The Times of India, paint a stark picture for ecosystems that buffer storm surges, filter pollution, and shelter fish and birds. Scientists warn that without intervention, much of this habitat could be permanently lost to the ocean.

Tracking two decades of change

Researchers from US institutions analyzed data from nearly 450 coastal wetlands, some monitored for as long as 20 years. The goal was simple: measure whether each wetland's surface elevation is rising faster than the sea. Wetlands can keep up with rising water by accumulating sediment and plant matter, a process called accretion. But when sea levels rise too quickly, or sediment supply is cut off, the wetland drowns.

The numbers are lopsided. Overwhelmingly, wetlands are losing ground. The study found that only about one in six wetlands is accreting fast enough to match sea-level rise. The rest are falling behind, with many projected to convert to open water in the coming decades.

Why wetlands are losing ground

Several factors are working against the wetlands. Rising global temperatures are accelerating sea-level rise, while human activity has altered the natural sediment flow that once replenished coastal marshes. Rivers that carried silt to the coast are now dammed and channeled, starving wetlands of the material they need to build elevation.

Compounding the problem, many coastal areas are also subsiding—the land itself is sinking due to groundwater extraction, oil and gas withdrawal, and compaction. The combination of land sinking and sea rising creates a double threat that many wetlands simply cannot outpace.

The study's authors note that the 16% of wetlands that are keeping up tend to share certain traits: higher sediment supply, greater tidal exchange, or more vigorous plant growth. These natural advantages could inform restoration efforts, but they remain the exception rather than the rule.

What's at stake

Coastal wetlands are among the most productive ecosystems on Earth. They act as natural storm barriers, absorbing wave energy and reducing flooding during hurricanes and nor'easters. They also sequester carbon at rates far higher than forests, making them critical to climate mitigation. And they provide nursery habitat for countless commercial fish and shellfish species.

Losing these wetlands means more than losing scenery. It means higher flood risk for coastal communities, diminished water quality, and a blow to fisheries that depend on healthy marsh ecosystems. The economic and ecological costs would be steep.

Officials and conservation groups have not yet released specific projections for individual wetlands, but the study's broad strokes are clear: the race is being lost at most locations.

What can be done

Restoration efforts are already underway in several states, including projects to reintroduce sediment to marshes, remove barriers to tidal flow, and plant native marsh grasses. These measures can help some wetlands gain elevation, but they are costly and time-consuming. The new data may help prioritize which sites are most likely to respond to intervention.

The study also underscores the need for larger climate action. Even if local restoration succeeds, wetlands cannot survive if global sea-level rise continues unchecked. The researchers are calling for integrated approaches that combine habitat restoration with emissions reduction.

For now, the message from the data is unambiguous: most of America's coastal wetlands are not keeping up. The question is how many can still be saved.

Next, scientists expect to refine their models to identify which specific wetlands are most at risk and which restoration strategies yield the best results. Coastal managers will be watching closely as they plan for a future with higher seas.