John Pardue reckons the wetlands of Louisiana's Gulf Coast have "another 10, 20 or 30 years, then they'll totally have disappeared." The director of Louisiana State University's Water Resource Research Institute paints a truly bleak picture: "New Orleans lies directly on the coast, and even relatively weak hurricanes will bring massive destruction to the city."

Hurricanes like Katrina and Georges (September 1998) veered off to the east when they hit land. Their course changed when they touched the land's rough-textured surface, which consists of a mosaic of waterways, grassland and sandbanks. That deprived them of their energy and the hurricanes then began to abate. Were these extensive wetlands to disappear, it would only be a matter of time until a hurricane struck the then unprotected city of New Orleans head-on.

So, can the birthplace of legendary southern jazz be saved in the long term? At present, parts of the city lie under meters of water. Construction experts fear that after the water is pumped out, many houses will be uninhabitable and will have to be torn down. Is it really practical to spend billions rebuilding New Orleans, if even worse catastrophes are likely in the near future? And there's little doubt that they will come: rising ocean-surface temperatures in the Atlantic and the Gulf of Mexico only increase the likelihood of ever-more violent hurricanes striking the southern states of the US.

"We'll build better levees"

"We can't imagine a future without New Orleans," says Pardue, countering such objections. "We'll rebuild the city, we'll pump out the water and build better levees." Of that there is no doubt. But the question remains, "is it realistic for people in coming decades to live in a city which is sinking below sea level?" It's a question the environmental engineer and expert in hydrological science for the Mississippi Delta doesn't like to answer. Plans for protecting and regenerating the wetlands were first developed by geologist Ivor van Heerden and other scientists back in the 1990s. "Only a large-scale coastal restoration can guarantee the survival of New Orleans," warned van Heerden. The South African born expert is part of the Hurricane Center team at Louisiana State University.

"We have to make sure, that the Mississippi is allowed to run off in places," van Heerden insists. Nowadays the major waterway is completely walled-in by levees in coastal areas. The enormous weight of sediment which the river carries out to sea in the Gulf of Mexico is key to the survival of New Orleans and other communities along a 100 kilometer stretch of the Gulf Coast. Without the system of levees, the Mississippi would spew forth its sludge in the towns and cities. But the levees also have one blatant disadvantage: the wetlands do not get replenished with natural sediment. They begin to subside, and gradually become flooded by the sea.

"We have to open the levees periodically"

These researchers believe that the wetlands' lingering death can be halted. Their plan envisages a regeneration of the wetlands, section by section, over a time period of two or three decades. "For this to happen, the levees of the Mississippi must be periodically opened at particular points," says van Heerden. If the marshes were flooded naturally, the input of sediment would prevent them from sinking further. But regional distinctions have to be made, says Pardue. "We can't avoid the fact that residents of the wetlands will have to be relocated and factories displaced."