Invasive species

Definition: An invasive species is a species that does not occur naturally in a specific area, and whose introduction and spread can cause harm to human, animal, or plant health, resulting in adverse affects to the environment and economy.

Many non-native species can coexist with native plants in the environment into which they were introduced. However, invasive species spread and establish themselves over large areas, persist, alter their environment, and pose a threat to native vegetation and habitats. For these reasons, it is important to identify, monitor, and control these aggressive species.

Example: The Zebra Mussel

Zebra muscle (Dreissena polymorpha)

Zebra Mussel

An example of an invasive species which you may have heard about before is the zebra mussel, which originally came from Russia. Once introduced to North America, the zebra mussel quickly spread throughout the five great lakes, and now over 100 lakes are infested with this invasive aquatic species. Zebra mussels change their environment by consuming live animals and algae in the water that once fed other native species, some of which have begun to decline in numbers due to this decrease in food supply. Also, zebra mussels attach themselves to many surfaces, such as pipes, boats, docks, rocks, slow moving animals, and even each other.

The Spotted Knapweed

The species we are concerned with is another invasive species, the spotted knapweed. The spotted knapweed is a purple-flowered weed, which is not native to North America, but was introduced about 100 years ago and has spread throughout both Canada and the United States.

Spotted knapweed (Centaurea maculosa)

Spotted Knapweed flower

Spotted knapweed has the ability to invade a variety of natural and semi-natural habitats including rangelands, fields, forests, prairies, meadows, pastures, and disturbed areas. It will outcompete native plant species, reducing native plant and animal biodiversity, and decreasing forage production for livestock and wildlife. Also, once established, knapweed roots give off a chemical toxin which inhibits the growth and germination of other plants, allowing knapweed patches to expand. For these reasons, the invasive spotted knapweed plant is considered a serious threat to many ecosystems, and several biological controls have been proposed in order to prevent this destructive weed from dominating and spreading further.