For the circle to remain intact, this balance must be maintained. It may look harmless, but purple loosestrife is another alien species now threatening the health of DuPage's woodlands. Loosestrife wreaks havoc by overrunning native water plants normally used by wildlife for food and shelter. Recently, much attention has been paid to foreign factors that impact wildlife. This is especially true in woodland communities.
Exotic plants compete with native species for resources such as food, water, sunlight and soil.
Because exotics often have few or no natural competitors to keep them in check in their new environment, they are able to deprive native plants of these precious resources. When exotics secure a resource monopoly, native plants can no longer grow. Depending on the type of plant introduced and the resulting changes, exotics can destroy a habitat if permitted to run their course. Naturalists from both the Illinois Department of Natural Resources and the Forest Preserve District of DuPage County consider the invasion of exotic species to be one of the most serious problems facing area woodlands. According to District Plant Ecologist Scott Kobal, more than 500 of the approximately 1,500 plant species in DuPage County are non-native.