What is an Invasive Species?

Invasive species have been characterized as a “catastrophic wildfire in slow motion.” Thousands of non-native invasive plants, insects, fish, mollusks, crustaceans, pathogens, mammals, birds, reptiles, and amphibians have infested hundreds of millions of acres of land and water across the Nation, causing massive disruptions in ecosystem function, reducing biodiversity, and degrading ecosystem health in our Nation’s forests, prairies, mountains, wetlands, rivers, and oceans. Invasive organisms affect the health of not only the Nation’s forests and rangelands but also of wildlife, livestock, fish, and humans.

A species is considered invasive if it meets these two criteria:

1. It is nonnative to the ecosystem under consideration, and
2. Its introduction causes or is likely to cause economic or environmental harm or harm to human health.

This definition is derived from Executive Order 13112 (PDF) ^\1, issued on February 3, 1999.

1/ PDF format links require the Adobe Acrobat Reader to view.