Alien Earthworms Threaten Our Forests One reason for their spread: Fishermen tossing bait By John Johnson, Newser Staff Posted Sep 6, 2011 1:01 PM CDT 4 comments Comments Earthworms at work and play. (AP Photo/Dean Fosdick) (Newser) – Worms may seem like they would be natural friends of the forest, but some alien invaders are causing problems in the Northeast, say researchers at Colgate University. When exotic species of earthworm are introduced to America's northern forests, they chow down on the organic "forest litter" on the ground, which not only raises the risk of soil erosion but changes the dynamics of the eco-system for native plants and animals, reports the BBC. And how do the non-native earthworms get introduced into forests? People, of course. "The main culprits are recreational fishing, gardening, composting, and the movement of egg cases on vehicles," notes PhysOrg. The Colgate researchers did a case study in the town of Webb, located in New York's Adirondack State Park. "A mail survey of town residents show that positive attitudes towards earthworms and their ecological effects lead to casual disposal or use of them," they write.