The purple loosestrife have gotten out of control in the continental US, and are taking over and choking out native species and altering the habitats.  Blossey et al. argues that the impacts of the purple loosestrife upon the environment are of great enough magnitude where it would be worth it to release another nonnative species, an insect, as a biocontrol method to attempt to reduce the population of the loosestrife and keep it under control.  The loosestrife have risen in both number and extent to which they alter the habitat they live in, and though it might seem that they would only impact other competing native plant species, they also have become enough of a problem where they also are hurting animal species, especially specialized wetland birds.  Though the introduction of other nonnative species may have unforeseen negative impacts, with so much potential in danger as a result of the loosestrife, the prospective benefits would outweigh the possible dangers.

Blossey, Bernd, Luke C. Skinner, and Janith Taylor. “Impact and Management of
Purple Loosestrife.” Biodiversity and Conservation 10 (2001): 1787 – 1807.
Web of Science. Web. 25 Sept. 2010.