It’s generally agreed that most of the earthworm species native to Canada were actually wiped out during the glacial period. Since then, new species have been introduced to the country, with at least 14 non-native species now tunneling their way through Alberta’s soils alone. To most of us, earthworms are an indicator of good (or at least improving) soil health. But, that isn’t always the case.
“We think that they’re good in agricultural systems, as most farmers probably know and agree with,” says Erin Cameron, a scientist on the Alberta worm invasion project. “It’s just when they get into forests that they seem to be causing some problems.”
“In most Canadian forests there’s a thick layer of leaves on the forest floor and earthworms consume those leaves and mix them with lower soil layers, like the mineral soil. And that affects species that rely on thick leaf litter layer. So, other soil invertebrates like mites and springtails, and some plants that require a thick leaf litter layer to germinate their seeds. Also some birds which nest in the forest floor.”
Putting leaf litter decomposition into high gear can have vast impacts on species that rely on it. Cameron listed just a few of those organisms, including invertebrates like mites and springtails, some plants the require thick leaf litter to germinate their seeds and birds which nest in the forest floor. Hence the project.
“We’re trying to figure out their current distributions in the province, what different groups are there and how human activity and habitat affect the distributions of species.”
Indeed, if you’ve ever watched an earthworm move, you might find it hard to believe they could spread all that quickly on their own. Research Cameron has been involved in suggests they might be able to move up to 17m per year, but conventional wisdom limits them to 5-10m per year. Then again, that’s without hitching rides on ATV tires and the coolers of fishermen.
“Our research suggests that the main ways that they’re moved are by anglers discarding their bait, and by the earthworms and their eggs being transferred with soil or on vehicles,” said Cameron.
If you like rooting around in the dirt, digital media and worm hunting, you might have a role to play in all of this.
The team behind the Alberta invasive worm project has actually sent out a call for help from the people of Alberta. Wherever you are, urban or rural, prairie or forest, north or south, you can submit data you collect on earthworm populations through the Worm Tracker app or the group’s online form.
“There’s a few different ways [you] can sample earthworms,” said Cameron. “Either by just flipping over logs and looking at them, by digging holes or by using a mustard and water solution, which brings the earthworms up from deeper layers.”
Beyond providing data, Cameron also recommends that prevent earthworms and eggs from being brought into the forest by cleaning off tires, and avoiding avoid dumping bait.