Invasive Species Across the Country: America’s Crossroads

Nonnative invasive species are a threat across the entire country and Rick Horton, NWTF regional biologist, reveals how dangerous they are in the Midwest states of Iowa, Illinois, Indiana, Michigan, Minnesota, Missouri and Wisconsin.

“In my opinion, invasive species are the greatest ecological challenge of our time," Horton said. "Without the natural controls provided by their regular predators, diseases or plant resistance, nonnative species spread rapidly and dramatically, often altering biological pathways and plant and animal interactions.”

An invasive species is a plant, fungus or animal that is not native to a specific location and has a tendency to spread and casue damage to the environment. Invasives affect the habitat of wild turkeys and other wildlife. They compete for resources and spell trouble for all native plants and animals by causing death or by degrading habitat.

“Most of the impacts on wild turkeys are indirect because of long-term habitat changes,” Horton said. “Buckthorn, garlic mustard and others make it difficult to regenerate oak forests resulting in fewer acorns and roost trees in the future.”

According to Horton, invasives are the second biggest cause of habitat degradation and loss in America’s Crossroads, surpassed only by habitat conversion to human development or farms. Lack of natural fire regimes, improper management practices and reduced water quality also contribute to habitat degradation.

The NWTF is taking the fight to invasives. As one example, NWTF Minnesota used grant funding from the Outdoor Heritage Fund to treat buckthorn on over 700 acres of oak woodlands on the Ereaux, Sartell, McDougall, Sponsa and Buckhorn Lake wildlife management areas. Now prescribed fire can be introduces to keep nonnative species in check while regenerating the oak stands.

This project and many others conducted by state or federal agencies are large-scale and not conducive to volunteer assistance. But Horton encourages all citizens to “become aware of invasive species, do what they can to prevent their spread and help eradicate them on their own property.”

Horton lists some of the most common and problematic species from the Upper Midwest:

  • Common buckthorn - An invasive shrub of hardwood forests that spreads rapidly, shading out native shrubs and forest plants. 
  • Garlic mustard - A very invasive vascular plant found in woodlands and forests that causes a decline in native herbaceous cover within 10 years, altering habitat suitability for native insects, forcing out birds and mammals. 
  • Emerald ash borer - The beetle bores through the bark of ash trees in its larval stage; the tree loses its bark in areas and eventually dies.  
  • Oak wilt - An invasive fungal disease that invades the water vessel of all species of oaks and eventually kills the infected tree.
  • Aquatic species like spiny water fleas, zebra mussels and Asian carp - The water fleas eat zooplankton, upsetting species in the food chain. Zebra mussels feed on nutrients in the water that other species need to live. Asian carp reduce food for native species and increase water turbidity. 
  • European gypsy moth - First introduced near Boston, Massachusetts, it's one of the most destructive forest pests in the U.S., killing more than a million acres of forest per year, costing a fortune in damages annually.
  • Sericea lespedeza - A warm season, perennial legume native to eastern Asia, first planted in the U.S. in 1896. It's unpalatable to native wildlife resulting in mass native species takeovers, and its deep tap root makes it drought tolerant, so it can outcompete many native plants.

If you want to take action and help combat the spread of invasive species in your area, Horton recommends following the guidelines below:

  • Learn to properly identify invasives, research treatment methods and treat nonnative species on your property.
  • Don't drive vehicles, including ATVs and mowers, through patches of invasives, and clean equipment of vegetation and dirt before moving to a new area to avoid the spread of seeds.
  • Don't plant ornamental invasive species in your yard where they can spread to surrounding wild lands.
  • Thoroughly clean boats of vegetation and drain live wells when traveling between lakes.
  • Don't more firewood from place to place as it can contain emerald ash borer larvae.
  • Don't harvest oak in the summer, doing so can spread oak wilt.
  • Burn prairies at the appropriate time to stop the spread of Sericea lespedeza.
  • Dispose of unused nightcrawlers and minnows properly. Do not simply dump them out. Nightcrawlers are not native and change soil structure while minnow water can contain other small invasives. 

If you’d like to learn more about nonnative species in your area, please consider the following:

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