Prevention Offers a Better Way to Deal with Invasive Species

The Argentine black and white tegu -- which grows to over 4 feet and east the eggs of other reptiles -- is becoming an invasive pest in Florida. Photo credit: © 2013 Karine Aigner and Ken Geiger for The Nature Conservancy

The Argentine black and white tegu — which grows to over 4 feet and eats the eggs of other reptiles — is becoming an invasive pest in Florida. Photo credit: © 2013 Karine Aigner and Ken Geiger for The Nature Conservancy

It wouldn’t seem that a crocodile has much to worry about from other predators. But South Florida has a way of accumulating exotic species and the latest arrival reaches over 4 feet in length and makes its lunch on alligator and crocodile eggs, along with insects and fruit.

The Argentine black and white tegu was most likely first released by pet owners, like so many of the exotic animals that are wreaking havoc in Florida’s wetlands, forests and neighborhoods, including the Burmese pythons in Bryan Walsh’s recent Time magazine article.

The hotline originally set up to take python reports is now getting many calls about tegus and Doria Gordon, director of conservation in the Conservancy’s Florida program, worries about their growing population. Crocodiles are a federally threatened species in Florida and alligators are one of the state’s conservation success stories, but she’s also concerned about sea turtles, which lay vulnerable eggs along Florida’s beaches.

Not Every Exotic is Invasive

Pet owner education can help slow the release of charismatic animals like tegus, pythons and boa constrictors, but the problem is hardly limited to pets. By intention or by accident, the world’s flora and fauna, like the world’s people, are moving around the globe at an ever-quicker pace.

But only about 10 percent of the species that find their way to a new environment actually become invasive. The most promising solutions probably lie in the unrecognized, behind-the-scenes work of prevention.

“The way to approach this issue is to be as proactive as possible,” says Gordon. “You assess which species pose the greatest risk of becoming invasive and you prevent them from coming in in the first place.” Australia and New Zealand have been leaders in this approach and Gordon borrows from their work, starting with risk assessment tools that have already proven accurate in predicting which species would become invasive.

Working with collaborators, she adapts the tools developed elsewhere for the climates and habitats found in the United States. Gordon works primarily with invasive plant species — think kudzu in the south, yellow starthistle and tamarisk in the west, water hyacinth in aquatic environments, plus many of the weeds that sap agricultural productivity. Risk assessment tools have also been developed for other groups like fish, crayfish, mammals, and birds.

Cooperation is Essential

Once the species most likely to get out of hand have been identified, Gordon and others work with regulators and policymakers to develop a consistent regulatory framework that keeps those species from getting a foothold.

In the Great Lakes region, for instance, it’s pretty much futile to try and prevent the introduction of an aquatic species that isn’t regulated in neighboring states, since they all share connected bodies of water. Today, each adjoining state and province still has a different list of regulated species, but the risk assessment tools that Gordon and colleagues like Lindsay Chadderton of the Conservancy and David Lodge of Notre Dame are working on could help change that, preventing — or at least slowing — introductions of the most expensive and damaging problem species.

In addition to regulatory approaches, Gordon has also worked with the horticulture industry to voluntarily steer consumers toward lower risk garden and landscape species.

So how do you tell which species pose the greatest risks? It’s a combination of factors that line up together: Does it reach reproductive maturity at a young age? How many offspring does it have? Can it survive winters or droughts in its new location?  How far does it spread? How fast can it grow? Is there anything in its new location that likes to eat it?

“The single biggest clue,” says Gordon, “is has it become invasive anywhere else?”

Posted In: Science

Marty joined the Nature Conservancy in January 2014 to write about TNC research and manage the Science Impact Project. She started her career in ecosystem ecology and climate impact research, but has focused on science communications since 1999. She’s now doing what she likes best – writing about cool science and helping scientists find and communicate what’s exciting about their work.



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