
NPS Photo
What is "invasive"?
Organisms which don't occur naturally in a particular area but have been introduced (intentionally or otherwise) by human activity are known as "exotic species," "non-native species," or "alien species." These terms are interchangeable. "Invasive" refers specifically to non-native species whose introduction causes or is likely to cause economic or environmental harm or harm to human health. Only a small portion of non-native species are well-suited enough to a particular environment to become invasive there. A tomato planted in an Alaskan garden is certainly an exotic species, but it's very unlikely that it could ever become invasive. Some garden plants, however, such as Yellow Toadflax (Linaria vulgaris, also called butter and eggs or wild snapdragon), are highly invasive and can wreak havoc on Alaskan ecosystems.