What are invasive species?

Species that have been introduced or moved, by human activities to a location where they do not naturally occur are termed “exotic,” “nonnative,” “alien,” and “nonindigenous.” Conversely, “native” describes a species living in an area where it is found naturally.

What problems do invasive species cause?

A number of invasive plants and animal species have been severe world-wide agents of habitat alteration and degradation, and competition for native species. They are the major cause of biological diversity loss throughout the world, and are considered “biological pollutants.” Their populations often rapidly increase, allowing them to disrupt native plant communities and crowd out native species. By changing habitat, they also affect species beyond those they may directly displace. They can cause problems for those who use natural resources, whether for recreational use of land or waters or industrial use of public waters. Once established, invasive species rarely can be eliminated.

How do invasive species move from their natural range to new, distant places?

There are many pathways of introduction that move species from their natural range to new, distant places. Most introductions are the result of human activities. Some introductions, such as common carp, buckthorn, and purple loosestrife, were intentional and have caused unexpected damage. Many exotic introductions are unintentional. Species are carried on barges, boats and trailers, animals, vehicles, commercial goods, packing materials, produce, footwear or clothing, and in ballast water of ships.

Ships take on ballast water in other countries for stability during the ocean crossing. This water is pumped out when the ships pick up their loads in Great Lakes ports. Many of the species, such as zebra mussel, ruffe, and spiny water flea arrived in the Great Lakes this way. But they are now being spread throughout the continent’s interior via boats and through other recreational activities.

Are most of the invasive species already in Minnesota?

Many of the worst invasive species are not known to be in Minnesota. Hydrilla, bighead carp, New Zealand mudsnail, and Emerald ash borer are in neighboring states or provinces.

Whose problem is it?

Invasive species costs landowners, resource management agencies, and others millions of dollars each year. Herbicides, labor, and research top the bill in fighting against plants which threaten to clog waterways, ruin fisheries, turn pasture to wasteland, compete with agricultural crops, shade out forest regeneration, and overrun natural areas. For many aquatic invasive species there is no known selective control, so the problems they cause continue indefinitely.

How can we stop the spread of invasive/harmful exotic species?

Get to know the common invasive threats. Inform friends and neighbors. If you see these offered for sale, explain the problem to your nursery, grower or supplier.

• If you find any on your property, consult information sources or contact a resource professional for control methods.