WHAT ARE INVASIVE SPECIES?
An “invasive species” is defined as a species that is:
1) nonnative (alien) to the ecosystem under consideration, and
2) whose introduction causes or is likely to cause economic or environmental harm, or harm to human health2.
Nonnative species refer to plants, animals, and microorganisms transported or established outside of their natural range due to the activities of humans, whether done so intentionally or not3. Other names commonly used for nonnative species are alien, exotic, and/or non-indigenous species. Not all nonnative species will become invasive, and not all nonnative species are undesirable in Hawai‘i. Agriculture in Hawai‘i, for example, is based almost entirely on nonnative plants. Many of the brilliant flowers such as orchids and anthuriums, and mango, coconut and banana trees which symbolize Hawai’i in the minds of visitors and residents alike are actually nonnative species (Miller and Holt 1992). However, those nonnative species that do become invasive can have significant negative economic, ecological, and human health impacts that have been extensively documented. It must also be noted that even species that at first may appear to be non-invasive may indeed become invasive given the right change in local habitat conditions. This might include the introduction of another alien species, environmental changes, or other factors that give it a biological advantage to allow for invasive proliferation. Because such changes can occur over a long time lag, or quite suddenly, any new introductions into the local environment warrant close scrutiny over time.
While the specific biology of invasive species varies enormously, some or all of the following general characteristics apply to many invasive species (both terrestrial and aquatic) worldwide:4
• adaptable to, and capable of thriving in different habitats and a wide range of conditions;
• have rapid growth rates of individuals, thereby able to displace other plants or animals;
• are easily dispersible to new localities; and
• have reproductive characteristics that allow for rapid population growth.