What is an invasive species?
“An ‘invasive species’ is a species that is:
1) non-native (or alien) to the ecosystem under consideration and,
2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.”
Federal definition established by Executive Order 13112, signed by President Clinton, February 3, 1999.
Click to go to the USDA National Invasive Species Council, What are Invasive Species? for more information on this definition.
Are all non-natives invasive?
No, all non-native species are not invasive. However, by definition, all invasive species are non-native.
Click to watch a 4-minute video on the definitions of “native,” “non-native,” and “invasives.”
Invasive species = non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health (U.S. federal definition)
Native species = has evolved in a given place over a period of time sufficient to develop complex and essential relationships with the physical environment and other organisms in a given ecological community (Darke and Tallamy, see “Native Tree” Defined)
Non-native species = not native (i.e., alien) to the ecosystem under consideration
Friends of Native Trees in Takoma 