Quotes of the Day

There's an illegal immigrant cruising its way up the Mississippi River. The Asian carp — a common name for a few separate but similar species of carp — was imported into the U.S. by Midwestern fish farmers in the 1970s. The fish fit perfectly into their native Chinese and Vietnamese habitats, where they've been raised in rice fields for more than 1,000 years. But in the U.S., floods allowed Asian carp to escape into the wild, where they quickly proliferated in the Mississippi River system, seizing food and space from outmatched native species. Voracious eaters, the silver Asian carp can grow to as much as 100 lbs. — and they have a habit of launching like missiles at the sound of a motor, braining unwary water skiers and boaters. Now the carp are on the borders of Lake Michigan, and scientists worry that if the fish establish themselves they could ruin the Great Lakes.

The threat is considered dire enough that the Obama Administration has spent nearly $80 million on Asian carp control — money that is overseen by an actual Asian carp czar. The Great Lakes states have filed federal lawsuits to force the Army Corps of Engineers to step up its anti-carp measures, while the shipping industry in Illinois has fought back against the Corps' plans to possibly shut the Chicago canal to keep out the fish. (The canal is the main route between the Mississippi River and the Great Lakes.) There's even an annual carp-hunting tournament held in the small town of Bath, Illinois, where the objective is to kill as many of the fish as possible — while in costume and hopefully while drunk.

Though the concern about the carp is rooted in fact, there's also an element of xenophobia to the big public reaction to the fish. Not only are Asian carp possibly dangerous, they're an alien, invasive species. Quite simply, they shouldn't be there. Invasive plants and animals are viewed as the enemy of nature, outsiders that wreck the balance of the environment and muscle out beloved native species. It has increasingly become the job of biologists and wildlife officials to root out the invaders and protect nature as it was meant to be; the U.S. Fish and Wildlife Service now spends more than $15 million on invasive control just in national wildlife refuges. "This whole native versus non-native dichotomy has really become established," says Mark Davis, a biologist at Macalester College. "Intended or not, that has become the dogma."

But a growing number of conservation biologists are beginning to question that conventional wisdom. In a commentary published in the journal Nature last week, Davis and 18 other ecologists called for a reexamination of the default dislike of invasive species. Their argument was simple: in a world where climate change, human population growth and globalization have fractured the environment and scattered so many species, the division between native and non-native seems more and more artificial. "The native versus non-native narrative is a comforting one, and it's proven successful in the past," says Davis. "But it's a 20th century concept that is losing its meaning now that we know every corner of the planet is affected by humans."

In other words, the very concept of 'nativeness' is becoming an oxymoron, perhaps for plants and animals as much as human beings. The effort to hold onto it — and fight invasive species — looks like a losing battle, and an expensive one at that. Davis and his co-authors point to the decades-long attempt in the American Southwest to uproot tamarisk shrubs, an alien plant that was, ironically, introduced from Eurasia and Africa in the 19th century. At first the shrubs were welcomed as shade trees for desert farmers, but when water began to run low in the 1930s, the tamarisk were indicted as "water thieves," and later, during the political fever of World War II, as "alien invaders." Despite the fact that recent evidence shows that tamarisks use water at the same rate as their native counterparts and that the shrubs also serve as a nesting habitat for the endangered southwestern willow, tamarisks are the object of a 70-year-long suppression project that cost $80 million between 2005 and 2009 alone. If tamarisks were people, they could probably sue under anti-discrimination laws.

Not only are attempts to eradicate invasive species often misguided, they're rarely effective. Of the 30 planned invasive plant eradications planned in the Galapagos Islands since 1996, only four have been successful. Instead of focusing on the increasingly meaningless categorization of species as native or alien, Davis and his colleagues suggest simply evaluating whether a plant or animal is good or bad for the surrounding environment. That doesn't mean ignoring an invasive species when it's clearly causing harm, like the alien zebra mussels of southwest Russia, which hitched a ride in the ballast water of container ships and have caused hundreds of millions of dollars in damage by clogging water pipes in the Great Lakes. But, they argue, invasive species should no longer be guilty until proven innocent. "It is time for conservationists to focus much more on the functions of species, and much less on where they originated," Davis and his colleagues write in Nature.

Not every conservation biologist agrees. A prominent 1998 study argued that invasive species are the second-greatest threat to endangered species after habitat destruction, and some researchers have estimated that invasive cause more than $100 billion worth of damage annually. "I think they downplay some of the problems and uncertainties," Jessica Gurevitch, an ecologist at State University of New York Stony Brook, said to Wired, responding to the new study. "That we should just get used to it is not correct."

Yet it is Davis and his co-authors who seem to have the more realistic conception of the place of invasive species. Thanks chiefly to human beings, the environment is changing faster than ever, and plants and animals are changing and moving in an effort to keep up. The concept of nativeness may now be as meaningless as the idea of wilderness — of an untouched, perfectly balanced slice of nature. Chances are that Eden never existed, and even if it did, it ceased to be the day human beings moved in. For better or for worse, we as a species now have the single biggest impact on the natural world, which means we need to take responsibility for the care of this unruly garden. And in the environmental triage to come, nativeness will fade away for plants and animals as it has with people. "We don't have the money to spend on this Sisyphean task of eradicating invasives," says Davis.

So we may need to get used to the Asian carp, the devil's claw plant and other reviled invasives. Have a little compassion. After all, human beings have spread to every corner of the planet, exhausting natural resources and displacing other plants and animals, which makes us just about the biggest invasive species on Earth.

• Bryan Walsh