Salty Coastal Marshes Are Moving Inland

July 18, 2022

LSU Department of Oceanography & Coastal Sciences Professor Emeritus John Day recently co-authored a study highlighting the nature of coastal wetland loss in Louisiana and around the country. The study was published on July 1 in Science Advances, a publication of the American Association for the Advancement of Sciences.

The results of the study demonstrated that salty coastal marshes are migrating inland. As sea level rise transforms current coastal saltwater wetlands and marshes into open water, the landward edges of those wetlands begin to encroach on other lands—thereby turning not only freshwater wetlands but in some cases, cropland, forests, pastures and other forms of upland, into saline coastal wetlands.

Two-thirds of coastal wetlands migration will come at the expense of their freshwater counterparts, while the other third will take over other types of uplands.

The study, which was led by the U.S. Geological Survey, looked at 166 estuaries on the Pacific, Atlantic and Gulf Coasts of the United States. It shows the inward migration of these salty coastal wetlands does not fully counteract the seaward losses, meaning the overall number of coastal wetlands will continue to decrease, even as they migrate inland.

The Louisiana coast is among the most affected by this phenomenon.

“Coastal Louisiana has one of the highest areas of wetland loss and landward migration of saline marshes will not offset coastal wetland loss,” Day said.

Day helped determine which wetlands in Louisiana were most likely to be replaced by landward migration of saline marshes, including helping focus attention on rice fields that would become more saline as sea level rises and the areas flood with salt water.  

Understanding the nature of the loss can help land managers and others better understand, prepare for and mitigate the ecological changes as saltwater wetlands continue to intrude.

This study is the first to fully assess and compare how rapid sea level rise will affect wetlands on the Pacific, Atlantic and Gulf Coasts. The full article can be found online at

Additional Link: 

Migration and transformation of coastal wetlands in response to rising seas, Science Advances:


Contact Bobbi Parry

LSU College of the Coast & Environment