Invasive Species Definition Clarification and Guidance White Paper

Weeds As Examples Weeds provide good examples to clarify what is meant by an invasive species because most people have a concept of what constitutes a " weed. " Invasion can be thought of as a process that in our example, a plant must go through to become a successful, yet harmful invader. Several barriers must be overcome for a plant to be considered an invasive weed. Invasive weeds are invasive species. Large-scale geographical barriers First, a geographical barrier must be overcome, which often occurs as a mountain range, ocean, or similar physical barrier to movement of seeds and other reproductive plant parts. Plants that overcome geographical barriers are known as alien plants or alien species. Alien plants are non-native plants and alien species are non-native species. Therefore, non-native plants are those that occur outside their natural range boundaries, and this most often is mediated by humans either deliberately or unintentionally. Survival barriers The second set of obstacles that a non-native plant must overcome is barriers to germination and survival in its new location. These typically are environmental barriers such as adequate moisture availability to allow successful germination and survival of seedlings that will continue to grow to maturity. Other physical barriers might be soil pH, nutrient availability, or competition for resources from neighboring plants. Preamble: Executive Order 13112 – 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. " In the Executive Summary of the National Invasive Species Management Plan (NISMP) 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. " To provide guidance for the development and implementation of the NISMP, the National Invasive Species Council (NISC) and the Invasive Species Advisory Committee (ISAC) adopted a set of principles outlined in Appendix 6 of the NISMP. Guiding Principle #1 provides additional context for defining the term invasive species and states " many alien species are non-invasive and support human livelihoods or a preferred quality of life. " However, some alien species (non-native will be used in this white paper because it is more descriptive than alien), for example West Nile virus, are considered invasive and undesirable by virtually everyone. Other non-native …