"Invasive species have been a problem as long as America has existed as a nation," says Thom Cmar of the Natural Resources Defense Council (NRDC). However, Cmar says that as transportation into the country has become more advanced, more invasive species have come in on boats and planes, thus worsening the problems posed to ecosystems.
These species have the uncanny knack of muscling out local competitors in the U.S., sometimes pushing commonplace species onto the endangered list by outcompeting them for food or resources. And as these creatures perpetually vandalize ecosystems, the U.S. has to shell out the money to fix the messes and restore nature's balance. Removing organisms that are numerous and evasive is no easy task, similar to finding a needle in a haystack, and so the U.S. focuses its efforts on border patrol, ensuring that no more of these species enter the country.
The NRDC advocates closing the routes that invasive species often use to hitchhike into the country, while the U.S. Fish and Wildlife Service, under the Lacey Act, regulates what people are legally allowed to bring in to the U.S.
"The costs of invasive species are so high, literally hundreds of billions of dollars a year," Cmar says. "Allowing these species to continue to come in and devastate our economy and ecology isn't an acceptable solution."
Of all the invaders, here are the worst of the worst, those that seem to be guests in the U.S. for the long haul, regardless of plans devised to be rid of them.