Invasive Species Management

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Invasive species are also known as non-native or exotic.  Invasive or exotic species are one of the biggest challenges currently facing natural resource managers. Invasive species threaten habitat quality, ecosystem processes, and biodiversity - all of which could potentially harm wildlife. Because of the threats invasive species pose to native plant communities and wildlife, control of exotic species is often a goal of natural resource management.


Lacreek National Wildlife Refuge has an aggressive exotic species control program to rehabilitate degraded habitats and prevent further spread of exotic species. A variety of exotic species including leafy spurge (Euphorbia esula), perennial sow thistle (Sonchus arvensis), and purple loosestrife (Lythrum salicaria) are currently being managed at the Refuge; however, the most troublesome is Canada thistle (Cirsium arvense). Canada thistle, a native to Europe, is believed to have been introduced into North America during the early 17th century. It has since spread throughout much of the central and northern United States and has become a noxious plant of range and grasslands.

The Refuge uses an integrated approach to control Canada thistle. Grazing, prescribed fire, herbicides, water management, and biological-control agents are utilized to control the exotic. While control of Canada thistle is ongoing, the Refuge is taking another more progressive approach to exotic species management. It is believed that grasslands with diverse plant communities are less likely to be invaded by exotic species compared to less diverse degraded communities. With this principle in mind, the Refuge is looking for long term ecologically sound solutions to exotic species problems by restoring degraded grasslands using prescribed fire and grassland reconstruction techniques. When properly conducted, prescribed fire generally favors native plants and improves vigor and species diversity within grasslands. Continued use and development of prescribed fire on the Refuge will improve the quality of grassland communities. Grassland restoration, including the conversion of agricultural fields and stands of exotic cool season grasses to native grasses, is also being undertaken to enhance diversity within upland areas. Read more about the grassland restoration program.