NPS. March 2005. Northern Great Plains Exotic Plant Management Management Plan and Environmental Assessment. 460 p.

The intent of this project is to manage exotic plants to reduce their negative effects on native plant communities and other natural and cultural resources within these parks. This Northern Great Plains Exotic Management Plan and Environmental Assessment (NGP EPMP/EA).

Exotic plants are species that occur outside of their native ranges as a result of direct or indirect human actions. Exotic plants replace native plant communities, degrade wildlife habitats, and reduce the biological diversity of ecosystems. For example, more than 20,000 acres (about 30%) of native habitats for plants within Theodore Roosevelt National Park have been altered by the spread of exotic plant species. Exotic plants are also affecting habitats of federally listed threatened and endangered plants. Both the Missouri National Recreational River and the Niobrara National Scenic River have sections of federally designated critical habitat for the piping plover (Charadrius melodus). Purple loosestrife (Lythrum salicaria), and aggressive exotic plant, is threatening this critical habitat. More that 2,000 acres of monotypic stands of purple loosestrife have been mapped at Niobrara National Scenic River and Missouri National Recreational River.