Vast tracts of the Mississippi are disappearing, threatening wildlife that inhabit the swamps. Matthew Brace reports on conservation attempts
THE fragile environment of the Mississippi river delta south of New Orleans in the southern United States is in crisis. Wildlife and the livelihoods of local inhabitants are under threat as large swathes of land disappear, under the waters of the Gulf of Mexico.

Up to 35 square miles of swamp are being lost each year, according to the Louisiana Department of Natural Resources which estimates that by 2040 another million acres will vanish.

The Mississippi drainage basin is the third largest in the world covering 1.25 million square miles, stretching up into Canada, east to the Appalachian Mountains and west to the Rockies. The river used to meander slowly through the final stage of its 2,500 mile journey, across the low-lying region around New Orleans, depositing silt and forming the series of low, unstable islands that make up the delta.

However, the high-banked levees, or dykes, that were built around New Orleans during the past 100 years to protect the city from flooding have forced the river into a faster-flowing channel through the delta swamplands and out over the lip of the shelf of the Gulf of Mexico at a rate of 600,000 cubic feet per second. As a result, the river's momentum is now too great for it to drop silt and the delta is starved of the essential material it needs to maintain its size and stay above sea level.

The delta crisis is expected to hit wildlife and have a knock-on effect on the seafood industry and tourism which are big money-earners for the native Cajun swamp dwellers.

This is one of the most ecologically sensitive wetland areas in the US, housing many animals and providing an important pit-stop for migrating birds. Alligators, white-faced deer, green-backed herons, frigatebirds and pelicans live here. Redhead ducks in their thousands come to winter each year, while summer sees flocks of royal and sandwich terns, laughing gulls and black skimmers.

Scores of swamp tours take tourists by boat cruising through the bayous. Captain Dave Turgeon, who runs nature excursions from his home in Lafitte on the delta, has seen his environment alter beyond recognition. "I've watched this whole area change so much and I'm only 35. My wife and I watched a point of land on Bayou Perot where we used to fish become an island and then disappear," he said. "There were live oak trees growing on the high points but they have all gone now."

Macon Fry, a travel writer who lives in a stilted house on the shores of the Mississippi, has seen the delta landscape change notably in recent years. "When I first moved here in 1982, the small creeks and bayous I used to fish on the delta were quiet backwaters. Now they are in the middle of lakes," he said. "And soon this is going to be affecting people's back yards. The delta acted as a buffer zone for hurricanes but now it is disappearing like this people are getting worried about the increased damage a storm might do if it hit."

Some areas close to where the delta sands meet the sea are now being restored using discarded Christmas trees lain across the streams and creeks which act as sediment traps when the water flows seaward, and allow the caught silt to flow back up to the bayous when the ocean waves crash against them. It's a slow form of sediment restoration but it seems to be working.

Another scheme being considered is to channel into the delta the sediment gathered in the Atchafalaya Basin, an off-shoot of the Mississippi further west. Those who know the Mississippi river best - the freight-boat pilots - say this flooding of the delta is just the best way the river has chosen to remind the American military, who are responsible for monitoring it, that it is in control of its own destiny.

Mike Pope, a pilot from St Louis, Missouri, who has spent 20 years on the river, believes Mark Twain was right when he said it cannot be tamed. "No matter what the US Army Corps of Engineers try and do to control this river - they can build all the levees they want and use all the technical genius they can get their hands on - but in the end the river will always win," he said.