I have read a number of articles that list earthworms as one of the top three non native invasive species in the United States
In the forests of Minnesota, the forest litter is naturally 7" or 8" deep. Plants have adapted to sprouting and growing in this environment. There were no earthworms in this area.There are places along rivers and lakes where fishermen have dumped their extra red wigglers. The worms are slowly spreading and eating the litter to nothing. The native plants can't sprout and grow in the litterless environment. The forests are changing. No one knows the final outcome.
Here's a link to an article from the Minnesota Department of Natural Resources.
http://www.dnr.state.mn.us/inv...
Bottom line: don't just dump your extra worms out until you check.
