'Jumping worms' a concern for invasive species expert in Sault Ste. Marie

Good for the garden, bad for the forest.

That's the tagline Colin Cassin, a policy manager with the Invasive Species Centre in Sault Ste. Marie, uses when he describes earthworms.

Most earthworm species in Ontario are invasive. In fact, scientists believe earthworms were largely wiped out in North America by the last ice age, 10,000 years ago. But they were reintroduced to the continent by European settlers in the 18th century.

Now Cassin is concerned about an Asian worm species commonly called "jumping worms" because of their more active and "wiggly" temperament.

Researchers and master gardeners recently discovered these earthworms in the Greater Toronto Area, and if people are not careful, they could hitch a ride to northern Ontario.

That's a concern, Cassin said, because they can change the complexion of boreal forests.

"They're great at munching away at the organic litter layer, although the leaves that are just starting to fall down and globally start to decompose now, when there's high earthworm abundance, they chew up like crazy," he said. "They degrade that litter layer and expose their soil, and that completely changes the dynamics of the forest."

Earthworms can travel short distances by attaching themselves to a person's boots, or hitching a ride on an all-terrain vehicle or other mode of transportation. They can travel longer distances, though, when contaminated soil moves from one region to another.

Cassin said it's difficult to remove earthworms once they are established in an area. But species like the "jumping worm" can stay out of northern Ontario if people avoid moving soil from one part of the province, or country, to another.

"So the key message from me today is prevention," he said.

Earthworms increasing their range

Justine Lejoly, a soil scientist with the University of Alberta researching the effects of earthworms on soil carbon dynamics, told the CBC she estimates that only around 10 per cent of the boreal forest currently has earthworms.

But Lejoly has projected that by 2050, most of the boreal forest will be invaded which means the boreal forest soil could potentially lose most of its carbon stock.

Erin Cameron, an environmental science professor at St. Mary's University in Halifax, who studies invasive earthworms, said that decrease in forests' carbon stock can speed up the impacts of climate change.

Cameron's models found that when earthworms were present, the forest floor's carbon stock was reduced by around 50 to 94 per cent after 125 years, but most of that reduction occurred in the first 35 to 40 years.

This means that boreal forests could emit a lot more carbon, in the form of carbon dioxide, into the Earth's atmosphere, than they are absorbing- andit would be due to invasive earthworms.