IPAW Working Definitions: What are we going to call them?

Jim Reinartz, IP A W Board and IP A W Science Committee

One of the tasks of the IPAW Science Committee is to develop a working list of the invasive plants of Wisconsin. The committee is reviewing the status of current invasive plant lists, and will develop a list of species of highest concern to IPAW. The committee hopes to prioritize or categorize the species based on their level of threat to Wisconsin native plant communities. The IPAW Science Committee is collaborating with GLIFWC, The Great Lakes Indian Fish and Wildlife Commission, to develop a survey of people who have experience with invasives. The survey will solicit input from a wide "panel of experts" to determine the relative threat posed by the invasive plants of Wisconsin. This approach is similar to the concept of developing an index of conservatism for native plants by averaging the opinions of a panel of experts about the ecological properties of the species. The survey is part of a process through which IP A W will develop an "Index of Invasiveness" analogous to the indices of conservatism that are being developed for the native flora.

As the committee began working on the survey, it was immediately apparent that one of the keys to development of a useful survey would be to precisely define the terms that IPAW would use to describe the invasive plant problem. Here is a DRAFT set of working definitions that the IPAW Science Committee has written, and some notes describing why the committee is recommending these definitions. Most words have multiple definitions" Our goal is, therefore, not to come up with the absolute true definition of a term, but rather to write definitions that serve the goals of IPAW well.

Invasive Plants are non-indigenous species or strains that invade natural plant communities and wild areas and replace native vegetation.

The mission of IPAW is "to advance understanding of invasive plants and encourage their control to promote stewardship of the natural resources of Wisconsin". IPAW is an organization that serves the people who care for, and care about, the natural plant communities of the state, and helps them do as good a job as they can at preventing the spread of introduced species that are reducing the quality of those communities. The main focus of the members of IPAW is really on plants that are "out of place" and destructive of our native communities. We use the word non-indigenous here in the narrowly defined sense of not belonging to the plant community in which it is a problem. For example, a species may be native to the state but not the specific geographic area or even plant community in which it is problematic. In this case the species is non-indigenous to a specific locality or plant community (say prairies), and could be called invasive in prairies.

Weeds are undesirable and troublesome plants growing in disturbed areas, especially cultivated ground.

Weedy is a term used by ecologists to describe plants having life histories that allow them to very rapidly colonize and reproduce in recently disturbed sites. A good, simple definition of this meaning of weeds is "Aggressive invaders of disturbed habitats". Many native plants (e.g. the ragweeds) are weedy in this ecological sense of being early colonists. The main focus of IPAW may not be on weeds other than those that are also invasive. For example some weeds of pastures are also invasive in prairies. The definition of weeds that may be most useful to IPAW is the standard definition of weeds as "bad", troublesome plants mainly associated with agriculture. IPAW can then use that definition to be clear that as a whole class, weeds are not the main concern of the organization.

Potentially Invasive Plants (for Wisconsin) are species that are invasive in parts of North America having similar climates and plant communities, and that are thought to have the potential to colonize and become invasive in Wisconsin.

Sometimes Invasive Natives are native plants that can become overly abundant in a plant community to which they are indigenous, often in response to a change in the disturbance regime.

Sometimes Invasive Natives (or perhaps some better term) is proposed as a category of plants that are indigenous to the plant community in which they sometimes become overly dominant. For example, in the absence off Ire, there are several species of shrubs, native to prairies, which can become dominant and destroy the structure of the prairie. The Science Committee feels that part of the IPAW membership managing native plant communities may be interested in the organization's help with these species. However, these plants are not covered in the proposed definition of Invasive Plants. There are practical reasons why we would not want these native species lumped with non-indigenous species on a list of invasive plants.

The IPAW Science Committee would value your comments on these draft definitions. Direct your comments to this newsletter editor (Jim Reinartz, jimr@uwm.edu, 3095 Blue Goose Road, Saukville, WI 53705).