DePaul University
Environmental Science Program and Public Policy Studies Program
Illinois Invaded:
Ecology, Impacts and Policy Approaches to Illinois Invasive Species Problem

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Definitions

Executive Order 13112 defines an invasive species as an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. Because a variety of definitions exist for several terms we use throughout this website, we have attempted to identify and combine (were appropriate) common concepts regarding the meaning of these terms in order to establish clear definitions for regularly referred to terms.

Invasive species – a species, usually non-native, that is able to establish itself within existing native plant communities and poses a threat to the structure and function of these communities.

Native species – a species that was present in the geographic region prior to European settlement or has arrived and established through natural means of dispersal.

Non-native/alien/exotic/introduced species – a species (and its associated biological material) that was introduced to a particular ecosystem or geographic region and is able to survive and reproduce in the introduced habitat.

Naturalized species – a non-native species or native species from another region of the country that has become established in a community.

Weedy – a [plant] species that grows rapidly and readily spreads, especially in disturbed areas, but generally does not pose a threat to the integrity of native plant communities.

Control - eradicating, suppressing, reducing, or managing invasive species populations, preventing spread of invasive species from areas where they are present, and taking steps such as restoration of native species and habitats to reduce the effects of invasive species and to prevent further invasions. (from executive order 13112)

Introduction - means the intentional or unintentional escape, release, dissemination, or placement of a species into an ecosystem as a result of human activity. (from executive order 13112)

(the above definitions are slightly modified from those given on Chicago Botanic Garden website)

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