Native earthworms from Canada were removed by the last glaciers and of the 19 species confirmed in Ontario, 17 originate from Europe and 2 from the United States. Since the retreat of the glaciers, the forested systems of Ontario have evolved without earthworms and their establishment in these areas significantly threatens the health of the forest lands.
Earthworms have the ability to ingest and mix soils and are known for their contribution as food for wildlife and for use as bait by anglers. Although in forests where earthworms have invaded, the forest dramatically changes by the absence of a leaf-litter layer and exposed mineral soil. There are no methods to control earthworm populations in natural habitats; preventing new infestations is the best protection.
Some earthworms have been found throughout much of Canada extending as far as our northern Territories of Nunavut and the Yukon, while others are limited to sporadic distributions only in the south. In Ontario, invasive earthworms can be found across the southern half of the province with some species extending north of the Canadian Shield, mostly where human populations have moved soil.
Impacts of Invasive Earthworms
- Earthworms consume the leaf litter of forests, causing tree seedlings, ferns, wildflowers, and potentially water quality to decline.
- Change the physical and chemical properties of the soil, adversely affecting many native species.
- Change soil structure, inhibiting the historical and natural functioning of forest systems.
How to Identify Invasive Earthworms
- Earthworms range from a few millimetres to 3 feet long, with the most common ones being a few inches in length.
What You Can Do
- When moving soil or plants be careful to avoid moving earthworms into new areas.
- Clean your boots! Soil on boots and equipment can easily transport worm eggs and other seeds into new areas.
- Dispose of bait in an area of known worm infestation such as the garden at home, rather than dumping bait on land in natural areas.
- Don’t move earthworms into new natural areas such as forests.
OFAH/OMNRF Invading Species Awareness Program. (2021). Invasive Earthworms. Retrieved from: www.invadingspecies.com.
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Header photo by Joseph Berger, Bugwood.org