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The Invasive Species Assessment Protocol: A Tool for Creating Regional and National Lists of Invasive Nonnative Plants that Negatively Impact Biodiversity

  • John M. Randall (a1), Larry E. Morse (a2), Nancy Benton (a2), Ron Hiebert (a3), Stephanie Lu (a2) and Terri Killeffer (a2)...

We developed a protocol for categorizing nonnative plants according to their negative impacts on biodiversity in a large area such as a state, nation, or ecological region. Our objective was to provide a tool that makes the process of identifying, categorizing, and listing nonnative plants that cause negative impacts to biodiversity analytic, transparent, and equitable and that yields lists that are useful to researchers, land managers, regulators, consumers, and commercial interests such as the nursery industry. The protocol was designed to distinguish between species that cause high, medium, low, or insignificant negative impacts to native biodiversity within the state, region, or nation of interest. It consists of 20 multiple-choice questions grouped into four sections, which each address a major aspect of a species' total impact and when combined yield an overall “Invasive Species Impact Rank” or “I-Rank” (high, medium, low, or insignificant). The nonprofit organization NatureServe is now using this protocol to assess the estimated 3,500 nonnative vascular plant species that are established in the United States to create a national list prioritized by negative impact on biodiversity. The protocol and additional information are available on the Internet at, and over 500 completed species assessments are available through NatureServe Explorer (

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Invasive Plant Science and Management
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