* An Invasive Species Assessment Protocol: Evaluating Non-Native Plants for Their Impact on Biodiversity
NatureServe, in cooperation with The Nature Conservancy and the U.S. National Park Service, has developed this protocol as a tool for assessing, categorizing, and listing non-native invasive vascular plants according to their impact on biodiversity in a large area such as a nation, state or province, or ecological region. This protocol is designed to make the process of assessing and listing invasive plants objective and systematic by using a specified set of questions and requiring documentation of the scientific information used to determine each species’ rank. Species (or infraspecific taxa, as appropriate) are assessed one at a time for a specified “region of interest” to determine an Invasive Species Impact Rank (I-Rank) categorizing the species’ negative impact on natural biodiversity within that region as high, medium, low, or insignificant.
The protocol is designed for assessing the biodiversity impact of those species considered non-native in a specified region of interest, or at least non-native in a portion of the region different from their native range.
Some but not all of the non-native species present in a given region of interest actually threaten biological diversity. The protocol can be used to rank and list the non-native invasive plant species that threaten biological diversity, which we define as those species that
1) are present but not native in the region of interest,
2) maintain themselves or recurrently appear in conservation areas or other native species habitats, and
3) negatively affect the native species and other natural biodiversity within the region of interest, generally by outcompeting or hybridizing with native species, or by altering ecological communities or ecosystem processes.
The Invasive Species Assessment Protocol consists of two yes-no screening questions and 20 weighted multiple-choice assessment questions grouped into four sections which address four major aspects of an invasive species’ total impact (Table 1):
I. Ecological Impact (5 questions; 50% of I-Rank Score) |
1. Impact on Ecosystem Processes and System-Wide Parameters |
2. Impact on Ecological Community Structure |
3. Impact on Ecological Community Composition |
4. Impact on Individual Native Plant or Animal Species |
5. Conservation Significance of the Communities and Native Species Threatened |
II. Current Distribution and Abundance (4 questions; 25% of I-Rank Score) |
6. Current Range Size in Region |
7. Proportion of Current Range Where Species Is Negatively Impacting Biodiversity |
8. Proportion of Region’s Biogeographic Units Invaded |
9. Diversity of Habitats or Ecological Systems Invaded in Region |
III. Trend in Distribution and Abundance (7 questions; 15% of I-Rank Score) |
10. Current Trend in Total Range Within Region |
11. Proportion of Potential Range Currently Occupied |
12. Long-Distance Dispersal Potential Within Region |
13. Local Range Expansion or Change in Abundance |
14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats |
15. Similar Habitats Invaded Elsewhere |
16. Reproductive Characteristics |
IV. Management Difficulty (4 questions; 10% of I-Rank Score) |
17. General Management Difficulty |
18. Minimum Time Commitment |
19. Impacts of Management on Native Species |
20. Accessibility of Invaded Areas |
