Invasive Plant Issues

The mission of the Rhode Island Invasive Species Council is to protect the biodiversity in Rhode Island. According to the Executive Order on Invasive Species, “Invasive Species means an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.” The Rhode Island Invasive Species Council will gather and convey information on the presence, distribution, ecological impacts, and management of invasive species; promote uses of native species and non-invasive alternatives throughout Rhode Island; and work cooperatively with researchers, conservation organizations, government agencies, the green industries, and the general public to identify and manage invasive species pro-actively and effectively.

Overall goals of Rhode Island Invasive Species Council are:

• To protect native biodiversity;
• To conduct scientifically based assessment;
• To promote the use of native and non-invasive alternatives;
• To manage and control invasive plants in minimally-managed habitats;
• To encourage research on control methods;
• To develop assessment of methods for potential invasiveness;
• To educate the general public;
• To work cooperatively among all involved parties.

Criteria for including a species as a non-native invasive species or a potentially invasive species in Rhode Island

These criteria are based on the criteria developed by the George Safford Torrey Herbarium at the University of Connecticut and reviewed and improved by input from many scientists, conversation professionals and nursery representatives. Additional input came from the Connecticut Invasive Plant Working Group, State Geological and Natural History Survey of Connecticut, the Connecticut Biodiversity Forum, and the Definition and Criteria Sub-committee of the Massachusetts Invasive Plant Committee, which includes representatives from the nursery industry. These criteria have been adopted in Connecticut and Massachusetts and proposed as the national model by the American Nursery and Landscape Association.
The criteria for Rhode Island have been amended by the Rhode Island Invasive Species Council, and include animals:

To be considered: Criteria that must be met:
Widespread and Invasive 1-9, 10A
Restricted and invasive 1-9, 10B
Potentially Invasive 1-5, at least 1 of 11 – 13

THE CRITERIA

For a species to be included as a Non-native Invasive Species or as a Potentially Non-native Invasive Species, it must be substantiated by scientific investigation (including herbarium specimens, peer-reviewed papers, published records, and other data available for public review) to be:

1. Non-indigenous to Rhode Island
2. Naturalized
3. Have the biological potential for rapid and widespread dispersion and establishment.
4. Have the biological potential for dispersing over spatial gaps away from the site of introduction.
5. Have the biological potential for existing in high numbers from intensively managed artificial habitats.
Further, to be included as a Non-native Invasive Species, a species must be documented to:
6. Be widespread in Rhode Island or at least common in a region or habitat type(s) in the state.
7. Have numerous individuals in many populations.
8. Be able to out-compete other species in the same natural community.
9. Have the potential for rapid reproduction and establishment in natural communities.

There are two subdivisions of Non-native Invasive Species. Those that are currently invasive, cause serious management concerns, or pose a serious threat to the biological diversity of the state and are widespread in Rhode Island are designated as Widespread and Invasive. Those that are equally invasive but currently have a restricted distribution in Rhode Island or occur in only a particular region or habitat type in the state are designated as Restrictive and Invasive. Species in the latter category may be reclassified as Widespread and Invasive if new populations are found or numbers of populations increase throughout the state.

10A. To be considered Widespread and Invasive, a species must be widespread in Rhode Island with many populations in minimally managed natural habitats.
10B. To be considered Restricted and Invasive, a species must be common in at least part of the state or a particular habitat type(s) in the state and with some populations in minimally managed natural habitats.

If a species meets the initial 5 criteria but does no, at this time, meet Criteria 6-9 (all), it may be included as a Potentially Invasive Species if it meets at least of the Criteria 11 – 13. In the past, some of these species have been considered invasive in Rhode Island, at least in part because they are known to be invasive in other regions and thus expected to be so here.
11. Have some populations in Rhode Island that have high numbers of individuals forming dense stands in minimally managed habitats.
12. Have the potential, based on its biology and its colonization history in the northeast or elsewhere, to become invasive in Rhode Island.
13. Be acknowledged to be invasive in nearby states but its Rhode Island status is unknown or unclear. This may result from lack of field experience with the species or from difficulty in species determination or taxonomy.

The List of Invasive and Potentially Invasive Plants

Careful assessment is needed to determine if all subspecies, varieties, forms and cultivars are equally invasive (This final statement is an amendment of the Connecticut and Massachusetts criteria, which state: “Species as used here includes all subspecies, varieties, forms, and cultivars unless otherwise noted.”)

Rhode Island Invasive Species Council
Lisa Gould, Coordinator
URI Cooperative Extension/Rhode Island Natural History Survey

Cristin M. Larson; The Garden Consultant and Landscape Designer