Science Nation - Invasion of the Earth Worms

Think of earthworms and a few things come to mind: they make great bait for fishing, they aerate the soil, and they're an excellent addition to a compost pile. But, what a lot of people don't know is many earthworms are actually invasive species. "The western Great Lakes region, which is the area we're focused on, has no native earthworms," says ecologist Cindy Hale, a research associate with the Natural Resources Research Institute at the University of Minnesota in Duluth. Earthworms may be small but when they take over a forest, the impact is dramatic.