The Dirt on Worms S.K. Worm, (the S.K. stands for "Scientific Knowledge”) is the mascot for NRCS conservation education. He says to get in the know about natural resources, you've got to get smart about the soil.

The NRCS website (http://www.nrcs.usda.gov/FEATURE/backyard/wonworm.htm) explains the wonders of worms. Worms can be beneficial to agricultural and garden soil. But worms in the woods may have a dark side because they are just too good at what they do.

Non-native earthworms were brought to America by the first colonists. Some probably arrived with mud-packed root-balls of transported plants brought from Europe. Ships traveling to North America used rocks and soil as ballast which was dumped on shore.

The effects of this earthworm invasion have been slow to show because the segmented worms don't spread rapidly on their own. The widespread use of earthworms as fishing bait has spread them to more remote areas. All common bait worms are non-native species.

There is growing concern about invasions of European and Asian earthworm species, especially in northern temperate forests of the United States and Canada. These hardwood forests have developed without earthworms. Around 18,000 years ago, thick ice sheets killed all the native earthworms in the glaciated areas of  North America. Because earthworms are extremely slow moving, recolonization by native worms is slow. Non native earthworms seem more adaptable to a wide range of environmental conditions.  Native North American species are less cold and dehydration resistant.  Native earthworms are still confined mostly to the Southeast and Pacific Northwest.

Forests ecosystems that evolved without earthworms depend upon fungi and invertebrate detritivores to slowly break down organic matter and gradually release nutrients back to the plants. These hardwood forests have thick forest floor layers that serve as rooting medium for many species of forest herbs and tree seedlings. Earthworm activities that create healthy conditions for farms and gardens may cause unhealthy conditions for forests. Earthworms have voracious appetites. In the most heavily affected areas, the invading worms have devastated plants and turned forest floors once covered with leaf litter into bare soil.

The West Virginia Native Plants Society has a web posting called The Trouble with Worms.

The leaf litter in a forest is comparable to the skin on an animal. It retains moisture, protects the organs (roots), breathes, prevents erosion, deters pathogens (non-native plants), and promotes seed germination. A nutrient balance has evolved in this stable system between the vegetation above ground and the enormous biosphere in and below the leaf litter. When that system loses its leaf litter it is like puncturing your skin. Erosion follows and nutrients bleed quickly from the soil. Such disturbance soon exposes the soil, making it available to non-native, invasive plant species, compaction, and run-off of rainwater, which would normally keep the soil moist. The disturbed soil and invasive plants soon alter the stable system, causing a decrease in the diversity of plant/animal relationships, which in turn begins a cycle of non-native invasions that tend toward monocultures. When worms devour the duff, they aren't just harming the flora-- the habitat for ground nesting birds, salamanders ... everything is also affected.

Given the slow migration of earthworms in soil, most experts agree that containing them is of lower priority than preventing new introductions. Without humans moving them around, earthworms move slowly, less than a half mile over 100 years. If we stop introducing them forest can be earthworm free areas for a long time. Help by getting the word out to the public.

• If you fish, do not dump your extra worms out on the ground in forested areas.
• Some of the traits that make worms ideal for vermicomposting—such as high reproductive rate and adaptability—may also make them potentially successful invaders. If you have a compost pile in a forested area, do not introduce additional non-native earthworms.

For additional information, go to:

The Trouble with Worms
By Dennis Burton, Director of Land Restoration, The Schuylkill Center for Environmental Education, West Virginia Native Plant Society Website.
http://www.wvnps.org/earthworms.html

Invasive Earthworms—A Threat to North American Forests
Plants & Gardens News | Volume 19, Number 1 | Spring 2004
Brooklyn Botanic Garden website
http://www.bbg.org/gar2/topics/essays/2004su_worms.html

Exotic Worms Killing Off. American Plants
John Pickrell for National Geographic News
http://news.nationalgeographic.com/news/2003/01/0102_030102_earthworms.html

America, Found and Lost
Charles C. Mann, National Geographic
http://www7.nationalgeographic.com/ngm/0705/feature1/index.html

Great Lakes Worm Watch
http://www.nrri.umn.edu/worms/default.htm

Contain those Crawlers http://www.nrcs.usda.gov/FEATURE/backyard/wonworm.htm

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