Worms come marching in
Migration to NWT is concerning scientists
Candace Thomson
Northern News Services
Published Friday, April 18, 2014
SOMBA K'E/YELLOWKNIFE
Earthworms are invading and it's no small issue, according to researchers who are concerned with the amount of earthworms showing up in places such as Yellowknife and Inuvik.
Researchers from the University of Alberta have announced that earthworms are showing up more and more frequently in the NWT, which isn't a good thing
for an environment not adapted to the presence of the worms.- photo courtesy of Wikimedia Commons |
There are no worm specialists in the NWT, but according to scientists from the University of Alberta, earthworms are invading here, Northern Alberta and the Yukon.
The earthworms are most frequently showing up in the North's heavily populated areas, such as Yellowknife, in gardens, along roads and at boat launches where fishermen often use them for bait.
A surplus of earthworms might seem like a good thing for the environment to most, but unfortunately that's not true, says one professor from the University of Alberta.
"People's notion they're good for the environment is correct if the environment is your garden, a field, an environment where all the other species have evolved in conjunction with earthworms being there," said Erin Bayne, a professor with the biological studies department at the Edmonton university.
"But these earthworms are voracious eaters of dead leaves, and the consequences is the reduction of leaf litter which in the boreal forest is quite deep. All the species (in the North) have evolved to live on deep leaf litter, and they're negatively impacted when that gets shallow."
Essentially, the earthworms eat the leaf litter until there's nothing left but the dirt floor. This is bad for plant and animal species which depend on the dense leaf litter for shelter.
"Any shallowly rooted voracious plant could be negatively affected - shrubs and trees not so much - but things like shrews could be negatively impacted because you go from lots of places to hide to an environment with a dirt floor," he said.
Bayne, who cautions against not taking the problem seriously.
"We worry a lot about declining species in our system, like caribou. But caribou, relative in terms of their impact on the environment, is relatively low. But with earthworms, where we think of them as benign, they can change entire species' communities," Bayne said.
"It is amazing, it depends on the density of earth worms, where you are, what forest type and what species of earthworms got in, but when you get a lot of earthworms, you can have hundreds to thousands per square metre."
Bayne decided to study the presence of earthworms in North America after he tripped over a log while on a trip in the bush, and found earthworms where he'd never seen them before.
It was surprising, he said, because earthworms haven't naturally been in North America - and especially not above the natural permafrost line - since the Ice Age.
"This is what the conventional wisdom is, that during the last glacial event, all earthworms would have been extricated from North America," Bayne said.
"We know they didn't show up until at least after European settlement, because the First Nations didn't talk about them until after then, so it's believed that original earthworms came from Europe. People seem to think that earthworms are part of the system, but that's just wrong."
Bayne said the worms aren't necessarily crawling up here on their own, but are being brought in, sometimes unknowingly, by humans.
"The juveniles are in a cocoon stage, almost like eggs, and one of those could easily get stuck in a tire tread. When they go from there into the soil, that would mean instant earthworm population," Bayne said. "Each cocoon could have up to 12 worms and the species doesn't require sex to reproduce. They can self-replicate with other individuals."
But why are the worms heading North? Bayne said a large part of it is that humans are making it easier on them, but it could also be from climate change.
"We've already proved you can regularly find worms above the line where the permafrost used to be - worms show up every spring in Inuvik, and if you can survive Inuvik, you can pretty much survive anything."
