What We Know

Quietly changing the face of our planet

These aren’t invaders from other worlds but unwitting travelers — organisms we have moved, by design or accident, from one region of the world to another.

Many fare poorly when introduced to a new environment, but some thrive when freed from native competitors, predators, and diseases. Left unchecked, they can transform entire ecosystems and out-compete or consume native species to the point of extinction.

Invasive species are a harmful subset of so-called exotic, alien, non-native, or introduced species, and are one of the most serious global environmental challenges we face.

An ever-increasing number of new invasions

© U.S. Geological Survey Archive, U.S. Geological Survey, Bugwood.org

They are not a new phenomenon, but the increasing globalization of our economy, with its extensive travel and shipment of goods, brings an ever-increasing number of new invasions. In the United States alone, scientists estimate that about 7,000 invasive species of plants, mammals, birds, amphibians, reptiles, fish, arthropods, and mollusks are established. Consider this:

  • The northern snakehead fish (Channa argus), an Asian native, was discovered in a lake in Maryland in 2002. Some species of snakeheads, including the northern, can move short distances across land and live out of water for three days. Officials feared this predator could move into other waterways and decimate a host of other species.
  • A series of aquatic invaders in the Great Lakes — including the sea lamprey, rusty crayfish, and zebra mussel — has caused catastrophic declines in populations of native species; introduced new parasites and diseases; and changed the way ecosystems function in this, the world’s largest freshwater resource.

More progress needed

Invasive species cost billions of dollars annually in damage and control measures. Zebra mussels alone were estimated to have cost the United States $750 million to $1 billion from 1989 to 2000. Current US laws and government programs are insufficient to guard against further introductions or control invasives that are already here. Whole categories of organisms are imported without regard for their potential invasiveness.

There has, however, been progress. Invasive species have gained new prominence in federal and state policy, and there is more cooperation among government agencies, trade organizations, and environmental groups. Thanks to scientists’ lobbying, the United States now has an interagency National Invasive Species Council (NISC), a National Management Plan, a Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW), and a federal Aquatic Nuisance Species Task Force. Moreover, some states are strengthening their own invasives laws, regulations, or policies instead of awaiting stronger federal action.