Oil spills have long been known to wreak havoc on coastlines, blackening otherwise sandy beaches and killing off birds, turtles, fish and other wildlife.

This time could be even worse. Louisiana’s coastline, which has become the latest battleground against oil’s slimy march, is made up of kilometres and kilometres of delicate marshland — shallow waters comprised of metre—high emerald green grass.

This habitat is a perfect breeding ground for small fish, shrimp and crabs that support a multimillion—dollar fishing industry. Exotic animals like alligators also reside in Louisiana’s swamps, while a huge variety of birds attract watchers to the state’s national parks.

Major oil spills, such as the 1989 Exxon Valdez spill off Alaska’s coast, can set back a community for a generation, but they do eventually recover. Oil can more easily be cleaned off of beaches in other southern states like Mississippi, Alabama and Florida.

But Louisiana’s fragile marshes face long—term destruction if the grass comes into contact with some of the heavy oil that is making its way through the Gulf of Mexico.

“These wetlands are very rich areas,” Ralph Morgenweck, senior science advisor for the US Fish and Wildlife Service, said in an interview. “Once the oil is in the marshes, it’s a much more difficult situation to try to remove it.” The primary hope is that it won’t get to that point. Oil giant BP, the Coast Guard, and even local fishing vessels are teaming up to keep as much of the oil offshore as possible.

So far, the oil that has been flowing from a ruptured well at the bottom of the Gulf, ever since the April 20 Deepwater Horizon rig explosion, has stayed mostly away from the coast.

But a few dozen oily birds, some turtles and jellyfish have washed up on beaches, while an untold number of fish are already dying in parts of the waters.

As of the weekend, there were 25 birds being treated and cleaned in wildlife centres, Morganweck said. Three have so far been released back into the wild. At least seven birds are reported to have died.

The marshes and swamps not only harbour wildlife, they protect the people on land nearer the shore. The wetlands act as speed bumps for hurricanes by absorbing some of the storm surge’s energy.

Erosion of this fragile ecosystem had been a problem long before the oil threat. The marshland is sinking under its own weight, aided by man—made canals and drilling rigs for oil and gas. Hurricane Katrina in 2005 worsened the problem by knocking down swamp trees.

The oil could easily exacerbate this situation, but so could the chemical dispersants being used to try to break up the dense oil in time to save the coast. This concerns many local residents.

“We’re hoping that it’s a clean clean—up,” said Katie Areas, owner of the Bouttes Bayou restaurant located on the edge of the marshes in Lafitte, nearly 50 kilometres south of New Orleans.

The Environmental Protection Agency, which gave BP approval Saturday to use dispersants deep under water at the source of the ruptured well, insists it is monitoring the effects closely. Agency chief Lisa Jackson said there are few good options when dealing with an oil spill off of Louisiana’s marshland.

“Dispersants are not the silver bullet,” Jackson said. “They are used to move us towards the lesser of two difficult environmental outcomes.”