Invasive Species Definitions Defined

Reading through some web postings, I note a tendency to define invasive species vaguely, a sort of know-one-when-I-see it vernacular. Akin to this laissez-faire definitional approach is the nigh unto gospel ‘resignational’ sigh that every plant is invasive somewhere so what is the problem. This resignation percolates into unexpected quarters, even rumored to infect the Nature Conservancy itself. Yesterday, we were told that there was no scientific evidence of invasiveness; today we are told that the non existent problem of yesteryear is far too big to be solved, and therefore logically we should continue as before, somewhat ostrich-like.

Difficult non linear problems, in the case of invasive species, a wicked inconvenience, need working definitions which are build by stakeholders finding common ground upon which to build consensus. As with making laws and sausage, the construction of common definitions is not a pretty sight and for some the resulting definition is too wide, to small, too unwieldy, to narrow, too inoperable, too controlled, too inaccurate; however it is something agreed upon which allows for a starting point in efforts to move forward together.

Executive Order 13112, for better or worse, currently, 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.” To clarify somewhat the term invasive species is further clarified and defined as “a species that is non-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.”( Invasive Species Definition Clarification and Guidance White Paper Submitted by the Definitions Subcommittee of the Invasive Species Advisory Committee (ISAC), Approved by ISAC April 27, 2006 )

At the heart of the defintional challenge are the complications explained in the white paper “…concerning the concept of invasive species (arising) from differing human values and perspectives. Differing perceptions of the relative harm caused or benefit gained by a particular organism are influenced by different values and management goals. If invasive species did not cause harm, we would not be nearly as concerned. Perceptions of relative benefit and harm also may change as new knowledge is acquired, or as human values or management goals change.”
The definition white paper explores the seeming incongruous notion that white-tailed deer are not invasive species on the east coast of the United States, and more importantly why they are not form a definitional point of view. I of course think of them as a scourge when they eat all the sweet corn but that is a different posting. The paper discusses feral animals versus domesticated herds, opening the door for irate supporters of the rights of feral cat to infest natural areas and decimate the ecosystem rather like the activities of the humans which brought them in the first place.

The white paper examines the negative impacts on ecosystem services which invasive species cause. The examples are extensive and worth reading in order to gain a context for the issues. The summary does a good job of laying out the case: “Invasive species are those that are not native to the ecosystem under consideration and that cause or are likely to cause economic or environmental harm or harm to human, animal, or plant health. Plant and animal species under domestication or cultivation and under human control are not invasive species. Furthermore for policy purposes, to be considered invasive, the negative impacts caused by a non-native species will be deemed to outweigh the beneficial effects it provides. Finally, a non-native species might be considered invasive in one region but not in another. Whether or not a species is considered an invasive species depends largely on human values. By attempting to manage invasive species, we are affirming our economic and environmental values. Those non-native species judged to cause overall economic or environmental harm or harm to human health may be considered invasive, even if they yield some beneficial effects. Society struggles to determine the appropriate course of action in such cases, but in a democratic society that struggle is essential.

Many invasive species are examples of "the tragedy of the commons," or how actions that benefit one individual's use of resources may negatively impact others and result in a significant overall increase in damage to the economy, the environment, or public health. In ISAC’s review of Executive Order 113112, the public domain is specifically represented; however, the implementation of the NISMP has prompted concerns over the rights of personal and private property owners. Property rights are of great importance in the U.S. and one outcome of the NISMP should be to recognize the right to self determination by property owners and promote collaboration on invasive species management. The right to self determination is an important concept in a democratic society, however, with that right comes personal responsibility and stewardship, which includes being environmentally responsible. The natural environment that our society enjoys, recreates in, and depends upon to support commerce must be conserved and maintained. Effective invasive species management is just one aspect of conserving and maintaining our nation’s natural environment, the economies it supports, and the high quality of life our society enjoys.” http://www.invasivespeciesinfo.gov/docs/council/isacdef.pdf

If you are new to invasive species issues, then the white paper is a good place to start your reading.


Invasive Plant Science and Management 1(4):414-421. 2008 doi: 10.1614/IPSM-08-089.1
Invasive Species Defined in a Policy Context: Recommendations from the Federal Invasive Species Advisory Committee
K. George Beck, Kenneth Zimmerman, Jeffrey D. Schardt, Jeffrey Stone, Ronald R. Lukens, Sarah Reichard, John Randall, Allegra A. Cangelosi, Diane Cooper, and John Peter Thompson*
*Professor, Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523; Lone Tree Cattle Company, P.O. Box 910, Bellflower, CA, 90707; Florida Department of Environmental Protection, 3900 Commonwealth Blvd., Mail Station 705, Tallahassee, FL 32399; Professor, Oregon State University, Department of Botany and Plant Pathology, Corvallis, OR 97331; Gulf States Marine Fisheries Commission, P.O. Box 726, Ocean Springs, MS 39566; Associate Professor, Center for Urban Horticulture, University of Washington, Box 354115, Seattle, WA 98195; The Nature Conservancy, University of California–Davis, Mail Stop 4—Robbins Hall, Davis, CA 95616; Northeast Midwest Institute, 218 D Street S.E., Washington D.C. 20003; Taylor Shellfish Farms, SE 130 Lynch Road, Shelton, WA 98584; The Behnke Nurseries Company, 11300 Baltimore Avenue, P.O. Box 290, Beltsville, MD 20705. Corresponding author's E-mail: george.beck@colostate.edu
Approved by ISAC April 27, 2006
Received: April 16, 2008; Accepted: August 2, 2008