Thu. Dec 7th, 2023

We would like to highlight one of the biggest threats to Ontario’s natural soil systems: earthworms!

Yes, you read that correctly. Many of us have a hard time imagining earthworms as a destructive force. After all, who hasn’t been told that they are natural composters, food for cheerful robins in spring and excellent recyclers in our gardens?

But there’s one important fact about earthworms that most people aren’t aware of: they’re not supposed to be here.

What once disappeared…

All of the earthworm species (and there are many) found in Ontario are, in fact, invasive species. Of the 19 species found in Ontario, 17 are from Europe and two from the United States. Any native earthworm species were probably wiped out long, long ago, when the ice sheets of Ontario’s glaciers first formed, about 75,000 years ago.

arctic landscape

When the glaciers retreated, they left behind worm-free ecosystems. Since then, over thousands of years, our ecosystems have evolved to recycle nutrients and decaying organic matter through a multitude of fungi, invertebrates and bacteria.

And then the worms arrived.

It is not a friend to all our native species.

Earthworms are what we call ecosystem engineers.

Like our beloved beavers, they have the ability to change the basic processes and structures of an ecosystem.

Worm in the ground.

They do this by digging into the ground and feeding on leaf litter found on the ground. These simple actions have serious impacts on soil structure and nutrient availability, thus affecting the plants that grow and thrive in those soils.

See also  Piping Plovers | Ontario Parks

Earthworms devour the leaf litter layer much more quickly than native decomposers, destroying the thick protective layer of decaying leaves that most of our native plants and insects depend on.

Leaf litter with young ferns

The roots of native plants have a difficult time growing in the dense soils produced by earthworms, while non-native plants that are better adapted to dense soils have an easier time establishing. Earthworms have been linked to many other invasive species and have already wreaked havoc on our local ecosystems.

Make love, not worms

Once an area is invaded by a species of earthworm, there is no known way to eliminate it. But the good news is that it is very easy to stop this invading force from squirming and extending its front lines.

Worms in the ground.

Earthworms move very slowly on their own; They are transported primarily through human actions.

At first, this meant hitchhiking on soils and plants brought by settlers and pioneers, either in the form of grown worms or in the form of egg sacs. Now earthworms are spread through gardening, vehicle and shoe tracks, transporting soil for construction and, above all, through fishing.

What the hell (worm) can I do?

Some simple ways to help stop the spread of earthworms and protect our soils are:

  • Avoid transporting soil, leaves, mulch and compost to different areas.
  • Wash the treads of your vehicles and shoes when moving from one area to another.
  • Throw unused bait in the trash, not on land or water. Even better, switch to artificial bait.

These small steps can make a big difference in Ontario’s forest ecosystems.

See also  It's aster season! - Parks Blog

Learn more about invasive species and the threat to Ontario’s biodiversity.