WELLS — The Ridgway’s rail is a rare bird that relies on salt marshes to survive. That’s why its future is in doubt: The salt marsh is disappearing under rising seas.

Scientists working with the federal government said the rail’s plight at California’s Seal Beach National Wildlife Refuge is indicative of what’s happening to salt marshes around the country.

Their assessment of eight of the country’s coastal salt marshes found that half will be gone in 350 years if they don’t regain some lost ground. The other four also are backsliding.

“That’s something that’s happening right in front of our eyes – an endangered bird that doesn’t have anywhere to nest anymore,” said Neil Ganju, the lead author of the study.

Salt marshes are ecosystems along the coast flooded frequently by seawater. They provide vital habitat for animals such as birds, crustaceans and shellfish, and are important for their role in protecting coastal areas from floods and erosion.

The U.S. Geological Survey set about to determine the danger that erosion poses to eight salt marshes on the two coasts. The group, led by Ganju, a Woods Hole, Massachusetts-based oceanographer, was surprised to find all eight marshes losing ground, including Rachel Carson National Wildlife Refuge in Maine. Their findings were published in January in the journal Nature Communications.

The report shows that salt marshes are not keeping up with the rise of sea levels, said Joe Kelley, a University of Maine professor of marine geology who was not involved in the work.

“Somebody in 50 years who looks at some of the marshes we’ve looked at, they’ll just see lots of open water,” Kelley said.