The 2010 Deepwater Horizon oil spill has been called one of the worst environmental disasters in American history — and more than six years later, scientists are still investigating how much damage it actually caused. Now, a new study suggests the spill may have permanently marred one of the Gulf shore’s most important ecosystems.  

The study, published Tuesday in the journal Scientific Reports, finds the oil spill caused widespread erosion in the salt marshes along the coasts of Louisiana, Alabama and Mississippi. And the researchers say there’s a chance these marshes might never completely grow back.  

Marshes “provide a variety of important services,” said lead study author Brian Silliman, a marine conservation biologist at Duke University. “They benefit humans, including acting as pollution filters, absorbing nutrients as they run off from the land before they get into the estuary, helping to suppress harmful algal blooms. They also act as breakwaters and buffer the shoreline from erosion.”  

They’re also important carbon sinks — in fact, research suggests that coastal wetlands may absorb several times more carbon per unit of area than tropical forests do. And they also provide habitat to a wide variety of animals that are staples of human fisheries, including shrimp, crabs and small fish.

So scientists have been concerned about how the marshes fared after the oil spill, believed to have affected at least 1,300 miles of shoreline from Texas to Florida.  

For the new study, the researchers investigated the relationship between the amount of oil that ended up on marsh grasses following the spill and how much these marshes eroded in the years since. Specifically, they looked at the height of the grasses and how high on the stems oil was found at each location. They analyzed data taken from more than 100 sites in Louisiana, Alabama and Mississippi.