Only a few forest stands are known to be affected to date, according to University of Rhode Island soil scientists Josef Grres and Jos Amador, but they say the threat to forests is real. Most of the earthworm species found in the Northeast are not native to the area.
Grres and Amador are evaluating the environmental impact of the common nightcrawler, one of the region's 16 to 20 species of earthworms. While the spread of the worms in Rhode Island has not yet been evaluated, the researchers note that bait cups littering popular fishing spots suggest that local forests may be affected soon.
"These exotic earthworms arrived here either in plant materials imported by European settlers, from fishing bait that escaped, and some that were imported here for use in composting," Grres said. "Any native earthworms that may have been in New England thousands of years ago were crushed by the glaciers."
When earthworms move into a new area, they feed on the organic material on the forest floor and bring it down into their burrows. They feed primarily on the top layer of leaf litter, as well as on the duff the spongy layer of decomposing vegetation beneath the leaf litter.
Grres said that while earthworms do an excellent job of recycling nutrients, "when they eat away the duff layer, all the plant seeds that germinate there, like trillium and mayflowers and wood anemone, may disappear or may not have any place to germinate. Other creatures that live in the duff and forest litter like salamanders and ground-nesting birds may be affected as we
Contact: Todd McLeish
University of Rhode Island