When earthworms invade a forested area, they consume the forest floor, and herbaceous plant diversity and tree seedling density decrease dramatically. Heavily impacted stands have been observed with only one species of native herb and virtually no tree seedlings remaining.
"Ninety-nine percent of the populations of native plant species normally found in hardwood forests, including large-flowered trilliums, yellow violets, and Solomon's seal, are destroyed in affected areas," said Frelich, a research associate in forest resources. "In many areas, the remaining bare soil is simply eroding away."