Invasive Species

Definition of invasive species

An invasive species is a non-native species that can become capable of establishing a native population and whose introduction causes or is likely to cause economic or environmental harm. This includes any viable life stages or parts of the plants that could aid in the dispersal of these species of plants, animals, and pathogens, none of which are native to the state of Wisconsin.

What problems do invasive species cause?

Invasive species are capable of causing extreme environmental problems. Without the checks and balances of the predators and diseases left behind in their native ecosystems, they out-compete our native species for food, water, and light. This can cause an imbalance in the ecosystem and permanently alter the function of the ecosystem that is under attack.

Why should you care?

If you enjoy being out on the water, invasive species such as Eurasian watermilfoil and curly-leaf pondweed can clog the motors on your boats. Boats and docks left in the water can quickly become encrusted with zebra mussels, which are difficult to remove. Eurasian watermilfoil, curly-leaf pondweed, and zebra mussels all make swimming very unpleasant. Rusty crayfish bully our native crayfish and destroy native vegetation, reducing habitat for our native fish populations.

If you enjoy hiking in the woods, buckthorn is a messy and thorny shrub that can fill in the entire understory of a woodlot. Buckthorn makes passage difficult, and negatively impacts the wildlife that also uses the woods. Garlic mustard will crowd out your prized trilliums and spring beauties and will also inhibit the growth of your maple trees. What fun is your woodlot in spring without the wildflowers and making maple syrup?

Wetland plants can consume entire wetlands and riparian areas. They choke narrow streams, preventing fish from moving through and can even prevent spawning. Nothing lives in the dense stands of phragmites, decreasing habitat for waterfowl and other wetland creatures. Japanese knotweed can create such a dense wall of stalks, it becomes extremely difficult to pass through.

The economic impacts of invasive species are astounding, too. A study from 2006 determined that the impacts of angling alone generate nearly $250,000,000 per year for the counties of Calumet, Fond du Lac, Winnebago, Waushara, and Outagamie. This could be lost if Lake Winnebago isn't protected from the additional invasive species which are already in Lake Michigan.

What can you do?

Prevent the spread of invasive species. For aquatic invasive species, there are a few simple steps. Inspect your equipment, remove any attached aquatic plants or animals, drain all water from equipment including live wells and buckets or containers of fish, don't move live fish or plants away from a waterbody and only buy minnows from a Wisconsin bait dealer. For additional tips on cleaning equipment visit: 

Protect Your Waters
Clean Boats Clean Waters

To prevent spreading terrestrial invasive species, the tips are similar. Clean all your gear before entering any habitat, clean all your gear before you leave. This includes everything from removing seeds and berries from your shoes and socks to cleaning the tires and undercarriage of your ATV. Do not move plant or animal material from one location to another.

For additional best management practices to prevent the spread of invasive species for recreational forest users, or forest and utility rights of way managers, visit the Wisconsin Council On Forestry.