HARI SREENIVASAN:

Gene Turner, one of the preeminent coastal scientists in the region, says Louisiana's coast is disappearing for several reasons:

First, the levees and dams built along the Mississippi to stop floods also stop crucial dirt and sediment from replenishing the wetlands. Second, not only are sea levels rising, but these wetlands naturally sink down a bit every year, bringing in more saltwater and further damaging the marshes.

And, third, ever since oil was discovered here, energy companies have dredged an estimated 10,000 miles of canals through the wetlands to move their drilling rigs into place. These canals degrade the marshes on either side of their banks, further weakening the wetlands, so when a big hurricane like Katrina comes through, the wetlands are torn up even more.

Virtually every coastal scientist here says dredging these canals has been a major contributor to Louisiana's land loss.