The invasion of non-native species

April 26, 2001

Heather Heilman

In Louisiana, one acre of land disappears underwater every 24 minutes. Nutria, those large, dimwitted "swamp rats" that have plagued the canals of Jefferson Parish also bear much of the blame for the state's disappearing wetlands. Nutria are voracious eaters of roots of the plants that would otherwise hold the soil together and prevent erosion.

The Mclhenny family of Tabasco sauce fame has long taken the blame for the state's nutria infestation. They imported nutria to Avery Island from Argentina in order to use them in fur farming. Some of the animals escaped in 1940. There is evidence, however, that some nutria had escaped or been purposely released from other fur farms before the McIlhenny nutria made their big break. So the McIlhennys are not solely responsible for the nutria problem.

The family, however, has contributed to the solution. Jack McIlhenny, who died in 1997, left a portion of his estate to be used for conservation and environmental concerns. That money is administered by the Coypu Foundation ("coypu" is the French word for nutria), which grants money to conservation efforts in south Louisiana.

The Tulane-Xavier Center for Bioenvironmental Research recently received a grant from the Coypu Foundation to develop a comprehensive approach to dealing with introduced species in south Louisiana. Introduced species are non-native plants, animals, even viruses, including nutria, Formosan termites, zebra mussels, water hyacinths and fire ants, that have been released here either accidentally or deliberately.

Many are harmless, but others can be environmentally and economically devastating. There are more than 900 species of non-native plants and animals in Louisiana. As a port, New Orleans is the point of entry for many introduced species, and it's also a crossroads for species moving from different directions.

"We import ideas, music, culture, food," said John McLachlan, director of the CBR. "But we're also a port of entry for species that come in through a variety of different ways."

One of those ways is in the ballast tanks on cargo ships. Ships use big tanks of water to balance their loads. When they arrive in port, they dump the water in the ballast tanks, also releasing organisms from their point of origin. That's how zebra mussels arrived in the Great Lakes, where they have clogged waterways. Now they're making their way down the Mississippi River, to New Orleans.

"Different species are going to be coming in no matter what you do," McLachlan said. "You can't stop it. So we have to come up with a long-term strategy where we can monitor what's coming in, predict where it's going to go, and intervene ahead of time."

The CBR team has begun to develop a map that summarizes how introduced species came into the area, where they are now, and the environmental and economic problems they have created. They plan to expand this research into a mapping system that models how species may spread.

"Based on the ecology that we already know, we should be able to tell whether it's going to be a threat or not, and if it's a threat, where the threat is going to come and how to get ahead of it," McLachlan said.

One of the objectives is to be prepared to handle new species as they arrive. Another is to stop the spread of some of the most pervasive introduced species that are already here, namely, nutria and Formosan termites. The CBR has been working with the United States Department of Agriculture's Southern Regional Research Center here in New Orleans to develop a novel strategy to stop the spread of Formosan termites.

"Based on the molecular biology we've been doing with hormones, we think we can find a way to either block or accelerate the metamorphosis of these insects so that we can bring down their reproduction," McLachlan said.

Eventually, this should lead to a method to treat wood with natural compounds that would interfere with the insects' hormones. CBR researchers also have been talking to their colleagues at the Endangered Species Survival Center about ways to cut down the reproductive ability of nutria.

"They're experts in assisted reproduction for wildlife, in how to fertilize wildlife eggs and carry them to term. We want to see if we can turn that technology around and use it to prevent nutria from reproducing," McLachlan said.
Nutria and Formosan termites are two species that have given Louisiana a painful lesson in how large the economic and ecological impact of introduced species can be. There's no more fitting subject of research for the CBR, according to McLachlan. "We're a natural laboratory here in New Orleans," he said. "We really have the opportunity to get at some significant questions that affect the region and the whole world."

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