Quirks & Quarks

Invasive earthworms threaten forest diversity

The ubiquitous garden earthworm is actually an invasive species, and is damaging Canadian forests by eating seeds and removing leaf cover.

European earthworms in Canadian forests are eating tree seeds

Stealthy European invaders (Edu-Pic.net)
Earthworms may be good for the garden, but a new study by Dr. Peter Kotanen, a biology professor from the University of Toronto, Mississauga, has found that the abundant invasive species is damaging forest ecosystems and changing forest diversity.

Much of the harm they cause is the result of seed predation, as well as the removal of the leaf cover that many plants rely on, in order to take root. The worms are eating the seeds of tree species, such as yellow birch and black cherry, as well as seeds of many wild flowers.

In an experimental area, the researchers found that over a two week period, 73 percent of seeds had been removed from the soil surface or pushed too deeply underground to germinate. 

Related Links

Paper in Biological Invasions
- University of Toronto release
- New Scientist story