Earthworms' underground invasion threatens North American forests

Science Daily: Earthworms have long been considered a friend to farmers and home gardeners, playing a vital role in soil quality. However, recent studies have shown that glaciated forests in North America—forests that evolved without native earthworms--now face the invasion of European earthworms from agriculture and fishing. This underground invasion has compounding impacts on the capacity of the soil to provide nutrients and sequester carbon—an important role as the world faces global climate change.

Kyungsoo Yoo, University of Delaware assistant professor of soil and land resources, and colleagues Anthony Aufdenkampe of the Stroud Water Research Center and Cindy Hale, an ecologist at the University of Minnesota Duluth, were recently awarded a three-year, $397,500 grant from the U.S. Department of Agriculture National Research Initiative (USDA-NRI) to study the quantitative coupling of the ecology of European earthworm invasion--specifically in Canada, New England and the Great Lakes region--with mineral chemical weathering and carbon cycling.

Prior to colonization, the glaciated areas of North America were devoid of native earthworms. European earthworms were first introduced to U.S. soils when immigrants brought crops from their native lands, harboring earthworm cocoons. Worms made their way to the edges of farmlands and to the forests.

In addition, these glaciated areas are pocked with small lakes; fishermen often dispose of unwanted live bait, infesting areas where native earthworms were not typically found. Unpaved logging roads through these regions also assisted the spread of non-native earthworms, as compacted soil on tires disperses cocoons and live earthworms.

“Gardeners and farmers all appreciate the beneficial effect of earthworms,” says Yoo, “However, there were systems where worms didn’t exist before and, as we have seen with other non-native invasions, there are ecosystem implications.”

Earthworm, photo by Luis Miguel Bugallo Sánchez (Lmbuga), Wikimedia Commons, under the terms of the GNU Free Documentation License, Version 1.2