What is an invasive?

According to the Invasive Species Act of 1999, an invasive species is an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. Invasives are introduced species whether they are nonnative, alien, exotic, or non-indigenous that have evolved elsewhere and have been purposely or accidentally relocated.

Why are invasives an issue?

While some species invasions occur naturally, the majority results from human activities. The movement of humans around the planet has drastically increased the rate and diversity of invasions. Introduced species may reproduce rapidly and spread quickly in the absence of natural enemies. To natural systems, they may:

* Compete with natives

* Decrease genetic diversity by mating with native species

* Introduce pathogens or parasites which are harmful to native species

* Disrupt nutrient cycles

* Change the timing and severity of floods and fires

* Change the overall look and function of a system

* Decrease biodiversity

Invasives are also a threat to agricultural systems where they may:

* Compete with crops for soil and water resources

* Interfere with the harvesting process

* Decrease the value of the land

How is an invasive different from a weed?

Some invasives are weeds and some weeds invasives but they are not the same thing. Weeds may decrease crop yields or quantity, reduce the aesthetics or functionality of landscapes and turf areas, or adversely affect human or animal health. But what is considered a weed and what isn't is an individual distinction. Invasives, however, are an established group of species which are known to be destructive to the tradition makeup of a particular ecosystem. It would be fortunate if all invasives were also seen as weeds. Unfortunately this is not the case. The appreciation of certain characteristics of invasive species supports their continued spread. Despite their recognized harm, many are still intentfully grown in gardens and distributed in nurseries.

What can I do to prevent the spread of invasives?

According to the Association for Biodiversity Information (www.abi.org) the most cost-effective solution to control of invasives is to prevent their arrival. Once exotic species have gotten hold of an area they often are capable of spreading with breathtaking speed, making eradication and control efforts difficult or impossible--and almost always costly. Being able to predict which species will become invasives is extremely difficult. We don't know why many species are invasives at the present moment. Furthermore, a species may not pose a problem until years after it's introduction. However, attacking the problem while it is still small and limited in range offers the prospect of total elimination, saving both money and natural resources. Early detection relies upon a well-informed public. Keep up to date with which invasives threaten your area. Encouraging others not to grow invasive species. If they insist, recommend that they remove the reproductive parts of the plant before wind and birds distribute the seeds. Petition your local greenhouses and nurseries to not offer invasive species.