The threat of invasive species

"I think we can be grateful that he was unsuccessful for a great many of those birds," said Lodge. "But he was amazingly successful with starlings, which are now one of the most common birds in North America, and a nuisance."

Today they number more than 200 million.

Most species were introduced for practical reasons, like the Asian carp, which was imported to clean catfish ponds in Arkansas.

"But, as is almost always the case, they escaped," said Lodge. "And it wasn't really until perhaps the 1980s that biologists in the Mississippi Basin realized this was a growing problem that was likely to get very severe."

Asian carp migrated up the Mississippi River to its tributaries, the Missouri and Illinois. Today only a series of electric barriers in Chicago's shipping canals separate the fish from the Great Lakes and its $7 billion commercial and recreational fishing industry.

Now consider kudzu, nicknamed the "Vine That Ate the South." Back in the '30s, the U.S. government paid farmers to plant this Japanese vine to control erosion.

John Taylor, who for years was a kudzu expert at the U.S. Forest Service, said the kudzu "began to exemplify the theory of unintended consequences very well. It got everywhere it weren't suppose to get."

Taylor says the vine, which can grow as fast as a foot a day, now covers up to 8 million acres of the south, snapping power lines and blanketing trees and even structures like a barn in rural Georgia.

The kudzu will "eventually cover the whole building and pull it down," said Taylor. "And you're getting kudzu bugs all over everybody."

Itself an invasive species, popularly known in the region as the stink bug, it invades homes in the winter.

"These little fellows like to overwinter in dwellings," Taylor said. "They create quite a furor when people are not used to having hundreds of thousands of these little critters invade their house. And when they're disturbed, their defensive response is a very offensive odor. You might sweep them out, but you'll get a surprise in the process."

As for the vine, Taylor says scientists DO know how to eradicate it ...

"The problem is spending the money that it would take to control large areas, and the time it would take over multiple years to control kudzu, it's not a feasible activity," he said.

The bill would run into the billions, which brings us to the national tab for invasive species.

Lodge says studies suggest the cost to the U.S. economy from invasive species are on the order of at least $120 billion annually ...

... like the $10 billion that cities will spend over the next ten years to treat or replace the millions of ash trees caught in the path of the emerald ash borer, a bug that likely found its way from China on wooden shipping pallets.

... Or the tens of millions of dollars spent clearing pipes and harbors covered in trillions of zebra and quagga mussels, brought to the Great Lakes on ships from Europe.

As the world grows more interconnected, Lodge says the problem will only grow worse. "There's just more opportunity now to move species - intentionally and unintentionally - around the globe," he said.

Few parts of the country have more experience with that than South Florida, through trade, international tourism, and international cargo. "And you have a climate where whatever gets here lives forever," said Adam Putnam, Florida's Agriculture Commissioner.

He said that in recent years, his state has endured infestations as exotic as Burmese pythons and Gambian pouched rats, to vital threats to agriculture like the Mediterranean fruit fly.

On his radar now: The giant African land snail, which can lay 1,200 eggs a year.

Homeowners described them as "slithery and juicy." "They have all kinds of fluids coming out." "For me, it's disgusting."

"With something like the snails we've got the trifecta," Putnam said. "It carries human Meningitis, so people are concerned. It eats 500 different plants, so agriculture's concerned. And it eats houses, so homeowners are very concerned."