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Experts worried about marshes
10/04/2002
NEW ORLEANS – A University of New Orleans geologist says the damage caused
by Tropical Storm Isidore to Louisiana's coastal environment was extensive
and whatever Hurricane Lili did Thursday could be worse.
"I would expect to see a lot of folded, floating marsh, a lot of torn up
marsh, a lot of sediment," Shea Penland said, nothing that Lili hit a
part of the south-central Louisiana coast that was "pretty marshy."
Dr. Penland spent two days flying over coastal Louisiana surveying
Isidore's damage.
"I was amazed at how extensive it was," he said.
He said he saw numerous new water channels cut through barrier islands
and extensive dune destruction. Two barrier islands on the map the
previous week, he said, "had simply disappeared."
Isidore resulted in parts of the levee system failing on Grand Isle and
in Slidell. It was not immediately know how the repaired levee on Grand
Isle fared, but Lili did cause flooding on the island Thursday. And a
levee was breached southwest of Houma, causing much of the small town of
Montegut to be flooded.
Effect on wetlands
What concerns a number of environmentalists are the increasing number and intensity of severe weather events projected because of global warming. Coastal wetlands are especially vulnerable, according to a detailed report for the Louisiana Legislature put together by a team of scientists and published by the Coalition to Restore Coastal Louisiana. "Coastal wetlands are already being lost at an increasingly rapid rate worldwide," the report warns. "Louisiana is clearly the state most at risk from further sea-level rise [and] erosion. Louisiana's coastal ecosystems are threatened with systemic collapse." But the long-term effects of storms such as Lili and Isidore may not be all bad, other experts indicate. "The wetlands tend to respond favorably to storms. Sometimes storms even help by dumping a lot of new sediment up in the marsh, and stirring things up," said Dr. Bob Thomas of the Loyola University Center for Environmental Communications. "Often what you see is the obvious natural resilience of the wetlands appearing after the storm." Hurricane Andrew hit coastal Louisiana after devastating south Florida in August 1992. The spiraling winds and storm surge created areas of open water in place of land. But after six months, Dr. Thomas said, he saw some of the land coming back. "Some wildlife die, but in general wildlife are genetically wired for these kinds of storms," he said. "Snakes and frogs get pushed around, but they just come bouncing back." Oxygen restored Hurricanes also stir up the Gulf of Mexico and at least briefly restore oxygen to the hypoxic or "dead zone," a large area of water depleted of oxygen that hovers just off the coast from the mouth of the Mississippi River toward Texas.The dead zone reached a record 8,000 square miles across this summer, extending west into Texas waters, said Doug Daigle, the southern hypoxia expert for the Mississippi River Basin Alliance. But a tropical storm and a hurricane in the course of a week should help, he said. "The dead zone gets broken up by storms in the fall. So when you get big storms like this, that accelerates and helps," Mr. Daigle said. Some hurricanes, like Juan in 1985, put a layer of mud all across the coastline, Dr. Penland said. "That was like a shot in the arm." When the tidal surge that accompanies such storms withdraws, it leaves behind a layer of mud that could help the marsh, he said. Glynn Wilson is a free-lance writer based in New Orleans.
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