The Washington area is known as something of a global melting pot for people, but it also holds a mixture of other species from around the world.
Biologist Jonathan McKnight is in charge of fighting invasive species with Maryland's Department of Natural Resources. His office is piled high with files and reports and a monstrous looking dead rodent staring down from a shelf.
"This guy here is the nutria, a 20-pound, this is a 20-pound on average swamp rat that was introduced from South America because everybody thought wouldn't it be great to have a whole new animal that we could make fur coats out of," he says.
McKnight says the nutria, with its long orange teeth and webbed feet, is an existential threat to the Washington region's marshes.
"These guys didn't just graze, they actually ate it, whole, they'd go into an area, eating it 24/7, they would leave a mudflat behind where there was a healthy marsh earlier," he says.
That's what invasive species do. Without any predators or parasites to stop them, they run amok, drive other life forms out and just mess up the natural balance.
"In most cases, an invasive species that gets into the environment and does well there, it's a lost cause," McKnight says.
In some instances, it could be said that invasives spur evolution -- they provide a new stress that creatures must quickly adapt to. But in another sense, some invasives are undoing evolution: They threaten to wipe out speciation and diversity that took hundreds of millions of years to create.
And, McKnight points out, humans may be the ultimate invasive species. Humans have increased the natural rate of extinction at least 1,000 fold, in part by introducing other invasive species.
In some cases, the genie can be put back into the bottle. For instance, McKnight says Maryland could eradicate the nutria in the next five years.
"We're using satellite imagery, GPS locators, radio telemetry, in combination with things like trapping of animals to remove them," he says.
It hasn't been cheap. It's taken a decade so far and nearly $2 million a year to do it. The best strategy, he says, is preventing invasives such as the nutria from ever getting here in the first place.