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Many Islands "Gone," Wetlands Gutted After Katrina, Experts Say

Adrianne Appel in Baton Rouge, Louisiana
for National Geographic News
September 19, 2005
 
Hurricane Katrina destroyed large swaths of wetlands and fragile barrier
islands off the coasts of Mississippi and Louisiana, scientists say.

The damage is drawing renewed attention to the role that human activity has had in weakening the coastal ecosystem. It also has raised the stakes on an ambitious 14-billion-U.S.-dollar restoration proposal that has been awaiting approval from the U.S. Congress since long before Katrina struck.

Aerial surveys show that Louisiana's barrier islands have sustained especially heavy losses from Katrina's scouring winds and waves.

Some island chains, like the delicate, crescent-shaped Chandeleur Islands off the southeastern coast, scarcely exist today.

"Right now they are essentially gone,'' said Robert Young, a coastal marine geologist with Western Carolina University in Cullowhee, North Carolina.

Although scientists have only begun to analyze the damage along the coast, their initial assessments are grim.

``I have never seen anything like it," said Young, who has been surveying the coast by air. "This is the most significant water-impact storm that I have seen, and I've been doing this for 20 years."

"Humans Are Partly Responsible"

In addition to their vital roles in the Gulf ecosystem, the barrier islands and wetlands also play a crucial part in protecting coastal communities from future hurricanes.

``The damage [from Katrina] may have been worse if those islands weren't there," Young said. "They may not have reduced the storm surge level, but they did reduce the wave impact on the inner shore.''

Now with many of the islands reduced to sandbars and with acres of marshes washed out, those natural defenses are gone.

And scientists are quick to note that the damage is not all Katrina's fault.

"We humans are partly responsible,'' Young said.

In its natural state the Mississippi River deposits sediments into the Gulf, literally shoring up barrier islands, Young explained. But the system of dams and levees built around New Orleans to keep floodwaters out has also kept the Mississippi from laying down fresh sediment.

``We've shackled the Mississippi, so sediment isn't coming down the river," Young said. "The sediment would add to the islands."

Without new deposits the islands have been rapidly eroding, laying them bare for a monster storm like Katrina, he said.

Katrina's storm surge washed away much of the islands' surrounding, stabilizing sand, especially on those islands with little vegetation. "It's a one-two punch,'' Young said.

Wetlands "Blown Away"

Katrina also damaged the Gulf's wetlands, a huge swath of marshes that makes up 40 percent of the wetlands in the U.S.

Gerry Duszynski, coastal restoration expert for Louisiana's Department of Natural Resources flew over marsh areas recently.

``At the mouth of the river you have seasonal plants that grow, but that's been blown away," he said. "You have freshwater plants, and they are all inundated by the [saltwater] storm surge."

The Gulf supports both freshwater and saltwater marshes, and neither has much tolerance for the other's preferred conditions, he explained.

"[The plants] have been completely blown out," Duszynski said. "We'll have to wait and see if it will come back next year.''

``On the natural islands in Mississippi the vegetation is brown because of salt water, the salt spray,'' Young noted. "You can tell a storm has come through."

Here too the marshes rely on sediments deposited by the Mississippi to grow. But because of New Orleans's levees and shipping lanes that have been dredged through marshes, the wetlands were shrinking well before Katrina struck.

``I think it'd be safe to say that [the shipping lanes] are an unmitigated disaster,'' Duszynski said. "It causes saltwater intrusion. It is a cancer on the inside of the wetlands. It's all-encompassing. We've been losing marsh from the inside and the outside."

But much of the damage, whether done by Katrina or by human interference, could be restored, he said.

``We can bring the salt marsh back,'' Duszynki said. "There are a number of ways—placing dredged material for a platform for the plants to grow on, … replanting, and freshwater diversion."

``We've got activities but unfortunately not the funding,'' he said.

Restoration Plan

Some restoration had already been underway before Katrina hit, Duszynski said, but it was on a small scale. What's needed now more than ever, he believes, is the passage of a 14 billion-U.S.-dollar federal proposal to restore the Gulf environment.

Drafted by the U.S. Army Corps of Engineers, the Louisiana Coastal Area Ecosystem Restoration Plan would launch projects big and small to rebuild barrier islands and replant lost marsh grass.

"Some of the projects are big and would take a long time to construct,'' Duszynksi said. Rebuilding the barrier islands, for example, would involve dredging sand from far offshore and delivering the sand to the islands.

Duszynksi said that "upwards of 15'' islands need to be rebuilt in this way.

The restoration plan was put before the U.S. Congress last year but has not yet been approved. Now it's likely to receive strong consideration, he noted.

``People are listening, and it's hot on the surface,'' he said. "[But] until we see some activity, we are still talking about it."

But not all experts agree that humans can or should restore what the Gulf has lost.

For his part, Young has doubts about shoring up the barrier islands.

"I'm skeptical about engineering solutions [to problems] that are caused by other engineering," he said. "We are blaming all this wetland loss on the levees at the same time that we are talking about raising the height of the levees" to protect New Orleans from future flooding.

"If we use federal money, I'd rather see a national debate about how to spend 14 billion dollars on a national protection program rather than a knee-jerk reaction as a result of the storm,'' Young said.

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