Earthworms’ underground invasion threatens forest sustainability

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. … “Soil scientists and agriculturalists recognize the benefits of mixing organic matter with the mineral soil in production agriculture,” Yoo says. “However, in native forests the leaf litter is essential to the survival of native trees’ seedlings. The litter layer provides protection for temperature changes and deer browse. As earthworms invade and consume the leaves, the layer and therefore the success of seedlings, is compromised.” He adds, “This relationship has been singled out as one of the most important factors impacting the future sustainability of forests in the glaciated areas in the U.S.”