Destruction of wetlands: swamp rats eating away at Louisiana′s fragile coastline | Environment| All topics from climate change to conservation | DW | 17.07.2019
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Invasive species

Destruction of wetlands: swamp rats eating away at Louisiana's fragile coastline

The US state of Louisiana has funded a program to slaughter nutria, or swamp rats, laying waste to the coastline. The animals eat the roots of swamp vegetation to the point they have no chance of growing back.

With its maze of swamps, bayous and marshes, southern Louisiana is a place where alligators laze with one eye open, egrets and herons fly among Spanish moss and where oak trees sprawl. It's a place of great natural beauty.

But that beauty is being eaten away by climate change, rising sea levels, increasingly dangerous tropical storms, oil and gas industries that dredge and cut into the land. And by the nutria.

About the size of a domestic cat, the animal also known as the swamp rat has brown fur, a beaver-like head and long and destructive orange incisors. It's those teeth and the animals' predilection for swamp vegetation that makes them a pest in the state of Louisiana, where coastal land loss is a real problem.

Read more: Germany's coastal lowlands under the shadow of climate change 

Liz Lecompte who grew up in the town of Lockport, Louisiana, lives about half an hour away from the current southern edge of the state's land. She worries about the young children in her family.

"When they are going to be in their 70s and 80s, they might not have no more Grand Isle, no more Golden Meadow, Leeville, Fouchon," she says listing towns near the gulf edge of the state.

Nutria eat the roots of vegetation in swamps, to the point that they have no chance of growing back. They can eat large swaths of marshes overnight, leaving open water in their path.

Nutria Biberratte Tier Nagetier (Fotolia/liveostockimages)

Nutria are eating away at Louisiana's coastline

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First brought to the region from South America by fur farmers in the late 19th century, swamp rats took to their new home easily. So easily, that their numbers exploded across southern Louisiana. That led to a booming fur business that thrived until the mid-1980s, when pelts fell out of fashion. As a result, nutria numbers soared, and the state experienced massive land loss.

Because the animals have no natural predators in the area, locals have, over the years, launched several initiatives to curb the population.

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The Louisiana Department of Wildlife and Fisheries has asked chefs around the state to put swamp rats on the menu, local fashion designers have tried to reignite interest in their fur, and SWAT teams have used the animals for shooting practice at night.

Of everything that's been tried, the Coastwide Nutria Control Program, which pays hunters and trappers 4.4€ ($5) for every nutria tail they bring in, has been the most successful. By 2002, the numbers had dropped.

USA Nutria in Louisiana (Annie Flanagan )

Nutria claw marks on a swamp boardwalk in Louisiana

Digging and hunting

Lecompte has seen plenty of nutria devastation first-hand. When the 12 kilometer (eight mile) Leeville bridge was built in 2009, it stretched over marshes to connect the main land of Louisiana with Port Fouchon and Grand Isle further out in the gulf water.

"Me and my uncle used to go trolling in his boat for shrimp in some of the little lakes right there by Leeville," she told DW. "Now the land is gone."

Listen to audio 06:46

Living Planet: When nutria takeover

The animals also left their mark on her family's land, digging tunnels in the levees that protect against flooding. 

"You'd be on a tractor," she said, "and you'd hit a hole and you could tell. Nutrias make a trail, you could see where it came up."

Because the area is so vulnerable to flooding, the few barriers they still have really need to be protected. So Lecompte, whose grandfather supported his family first by selling swamp rats to the fur industry and later to the Nutria Control Program, took to shooting the animals herself.

"When they did have plenty nutria I'd just ride the side out on my four-wheeler, you'd see them out on a hill or something like that and pop pop pop."

The incentive program has been so successful in her area, that the population on her property has decreased dramatically.

USA Nutria in Louisiana (Annie Flanagan )

As nutria populations are scaled back, this swamp vegetation has a chance of survival.

Transformation of a swamp

But about an hour north of New Orleans is the Hammond Assimilation Swamp, where the animals persist in greater numbers. Nick Stevens works in the Biology department at the Southeastern University of Louisiana and monitors the swamp. He says the nutria have contributed to rapidly turning the 800 acre swamp into an open lake.

Read moreLand loss threatens indigenous communities worldwide

"They've eaten the plants that hold the marsh together and when you have no plants holding it together it fragments, breaks apart and dies," he said.

Part of the problem is that they reproduce at such prolific rates.

"Every six weeks they can have a litter and the litter can be up to 8 to 12," Stevens told DW. "They can get pregnant 12 hours after giving birth, so it is literally rabbits. They just produce."

Stevens says efforts to control the population here have sometimes been feverish, with as many as 10,000 of the animals shot in a single summer. But he and his colleagues also cover the bases of young trees so the nutria can't eat them.

USA Nutria in Louisiana (Annie Flanagan )

Nick Stevens built this boardwalk into the Hammond Assimilation Swamp

When Stevens steps onto a floating marsh and jumps up and down, the land moves beneath him like a water bed. It's a good sign. Now that the nutria population has been so resolutely scaled back, swamp vegetation like these floating marshes stands a chance of slowly coming back.

But the fight to save the coast is far from over. There's an adage in Louisiana that the state loses a football field of land every 15 minutes. Stevens says that's now slowed to something like a football field ever hour.

"It's not that we're doing better," he said, adding that all the fragile parts have already been lost. "It's that now we're starting to eat land that is people's homes."

Nutria may no longer pose the same threats they once did in some areas of southern Louisiana, but in others, swamp monitors remain on the lookout for another outburst of little rodents with giant appetites for coastal flora.

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