Ideas - Why everything you thought about earthworms is wrong

Episode Date: March 30, 2026

Earthworms are supposed to be a sign of healthy soil. But they're actually an invasive species that can even damage forests. So have we been sold a lie about worms and soil? Not exactly. The relationship between the two depends on the context. And the way we garden — or farm — can make all the difference. IDEAS producer Annie Bender unearths the complicated truth about the not-so lowly earthworm.Guests in this episode:Joshua Steckley is a political ecologist, postdoctoral fellow at Carleton University and the author of The Nightcrawlers: A Story of Worms, Cows, and Cash in the Underground Bait Industry.Peter Groffman is a professor at the City University of New York Advanced Science Research Center and Brooklyn College, with research interests in ecosystem, soil, landscape and microbial ecology, with a focus on carbon and nitrogen dynamics.Mike McTavish is a conservation scientist at a rare Charitable Research Reserve in Cambridge, Ontario.Janet Browne is a historian of science and Darwin biographer, author of a two-volume set called Darwin: A Biography.

Jacqueline Furland Smith, a 40-year-old former Canadian military trainer, moves to Costa Rica to follow her dreams, but in the summer of 2021, vanishes without a trace. How can a woman just go missing and us put out all that effort to find her, and she's still missing? I'm David Rigen, and this is Someone Knows Something, Season 10, the Jacqueline Furland-Smith case. Available now on CBC Listen and wherever you get your podcasts.

This is a CBC podcast. In the spring, I looked out of my garden, and by the fence I saw two enormous worms. How big were they? They were as big as a tree. What did you do? I smiled scarcely. Welcome to ideas. I'm Nala Ayyad. How would you explain what a worm is?

A pink bug. Worms are actually not a bug. No, it's a pink kind of, like, long bug. Take a moment and ask yourself. What do you know about earthworms? They live in dirt. They eat it by birds, and they are really yucky. They're very sloppy.

It looks like a pink nuisance. Sometimes people call them worms. For many of us, of all ages, the answer is not a lot. If you don't see them, you don't think about them. It's really just earthworms in the garden, earthworms on the sidewalk after a rain. They don't do much. They're just sort of worms. And whatever you do think you know about them,

you may want to think again. The biggest misconception would almost certainly be that they're always a good indicator of a healthy soil. I didn't assume that they were, invasive, that they're an exotic species. Earthworm invasions contribute to global warming. Ideas producer Annie Bender realized just recently how little she knew about earthworms. I think of worms as all being kind of one thing.

They're long, they're pink, they're, you know. No, no. She's been on a journey ever since to unearth the full story. I want to complicate people's narrative about the worm a little bit here. What's your name? Suzy. Can I ask how old you are? Three.

You're three. And can I ask, do you like worms? No. Why not? Because I don't like when they touch me. If you ask a kid about earthworms, there's a good chance you'll hear one of two things, either that they're super gross. I don't really like them because they're very gooey. or that they're helpful for the soil.

Are worms good for gardens? Yep, they're good, really good. Yeah? They make the soil good? That's probably it. You probably know this too, even if you don't know exactly how you know it. Hi there. Can I stop you for a sec?

I'm just looking to talk to people, people that I'm running into you on the road. about earthworms? What do you know about earthworms? Just that they help the humus in the soil. They help add nutrients to our soil, so I know that for sure. They help sort of decomposition of the earth and creating a healthy soil.

I know they're good for us. They help. They help. But for thousands of years, our soils here in Canada did just fine without them. Our soil, if we're talking about Canada in the northern United States, would have been covered with a glacial ice sheet up until 12,000 years ago. That ice sheet would have made it uninhabitable for any kind of native earthworm species to exist. So you have a wide array of, let's say, pre-contact indigenous agricultural systems that got along seemingly just fine without the earthworm in their soil, whether that's hunting in forests that didn't have any worms or fishing without using worms as a bait, obviously, growing varieties of corn and beans and squash, tobacco, sunflower, wild rice, a huge array of agricultural practices, all of which would have happened without the presence of earthworms in the soil.

Joshua Steckley is a postdoctoral fellow at Carlton University. He studies the interactions between earthworms and capitalism, which, as it turns out, go back centuries. The Hudson Bay Company is created in 1670 by King Charles and effectively gets a monopoly over a third of what is now Canada's surface area, particularly for the lucrative fur and pelt trade. So you have to imagine that there are these big merchant ships coming from Europe with their hulls filled with ship ballast made up of rocks and soils to help stabilize the ship as it made their voyage. And then when they would enter the shallow waters of James Bay or other maritime ports, they would then dump this ballast at the port and then fill up their ship with all the valuable cargo like wood and metals and the precious beaver pelts and other furs and things like that.

But it's really when they're dumping the ship ballast, you have all this European material of soil and rocks and insects and worms that are mixing with these new landscapes. So at the time, if you wanted to see a worm in Canada, in colonial times, you would have to go to one of these ports. Did the settlers who arrived your notice that the soil didn't seem to have any worms? The Attorney General of Ontario wanted to get to know more about the resource potential of Northern Ontario. So he sends a guy up to write a report. And the guy is looking at mineral deposits and stuff like that. And he makes this funny observation. Yeah, he said, accepting at the Hudson Bay Company ports,

I don't think I've seen a single species of earthworm. He noticed it. So he noticed it. And there's some debate about whether they purposely introduced earthworms into the soil because they knew of the benefits that earthworms bestow or if it was just purely accidental. Like you're bringing your own crops, your own soil, your own seedlings, your own fruit trees, and hitching along for the ride is earthworms and earthworm cocoons. So I think that is the more likely explanation that they were accidentally introduced into these

landscapes that had not had earthworms, and they just thrived. Who do you relate to earthworms? When you see one, how do you feel? about it. I turn over the soil in my garden and I see an earthworm and I say, oh, good, I must have healthy soil. There's an earthworm in it. And I think that the earthworms are an indicator that my soil has organic matter in it, that my soil is in physically, chemically, and biologically good condition. And the earthworms are benefiting from that. Peter Goughman is a soil ecologist at City University in New York. I don't think that the earthworms necessarily contributed to that soil health,

but they're a symptom. And so how do I relate to them when I see them? I think, oh, that's good. It means I have a healthy soil. I have to admit, this assessment of earthworms by a soil ecologist caught me by surprise. It seems like you're saying earthworms are not necessarily even good for the garden. So I need you to help me understand that. They can be good for the garden if the soil is compacted. And so earthworms can really help with rehabilitation of damaged soils. And they're great in a compost point. So I think in a compost pile, you really want to accelerate organic matter, decomposition, and the formation of compost. And there have been a lot of studies about this in agricultural fields, if the soil is not compacted and if there's adequate organic matter, the earthworms are accelerating the decomposition of organic matter.

And so you lose carbon, you get increases in nitrous oxide emissions. And I think the evidence is mixed, but they are not necessarily positive in gardens or in agricultural fields, because if the soil is well managed, you don't need help in doing that. Peter isn't saying that we've been sold a lie about worms and soil. He's simply pointing out that the relationship between the two depends on the context.

And the way we garden or farm can make all the difference. What makes the earthworm so critical to contemporary agriculture, is farmers generally more and more, I think the majority now, practice no-till agriculture. So often we think of farmers still tilling the land, you know, with a John Deer tractor or something like that. But actually, they're not tilling up the soil as much as they used to. So farmers will harvest their plant, and depending on what it is, they'll keep some of the residue on the ground.

And that actually is feed for the soil. so they actually help the farmer incorporate that residue back into the soil and turning it into usable nutrients. It's just unfortunate in forests. They do the exact same thing, but you're actually then destroying the ecosystem that had evolved without the worm. Okay, so I'm going to ask you to describe where we are right now

and what we're looking at. We're at Rare in Cambridge, Ontario, and southern Ontario. We're near the confluence of the Grand and Speed Rivers. So we're looking out on sort of a mixed meadow kind of forested stand leading up onto the ridge. All of it's covered in maybe a good foot of snow right now as well. So we're probably actually looking at thousands and thousands of earth rooms right now, but they're down in the ground and they're inactive, and we won't be seeing them at the surface doing anything until things warm up in the spring.

Mike McTavish is one of the few people I've ever met who say, thinks about earthworms in the middle of winter. My name is Mike McTavish. I'm the conservation scientist at Rare. We're a land trust and environmental research institute. I run our research and ecological monitoring programs here. How deep would you have to dig to find a worm right now? It really depends on the species.

So some burrow deeply to try and avoid the coldest temperatures and basically wait it out until things start to warm up in the spring. Some will do that same thing, but at a different life stage, so not as an adult worm as we would think of it, but actually more as a cocoon. They can often be a little bit closer to the surface as well. So maybe top 10, 20 centimeters as opposed to something much deeper. Some of these species can be the order of meters deep,

depending on if they have the right soil conditions to burrow that far down. Wow. And do they get cold? You'd have to ask them, but presumably. If we were to continue down this forest path that we're looking at, and one side of this path had soil in which earthworms had been living for, say, a decade. And on the other side, the soil was completely intact without an earthworm in sight. How different would the two sides of this forest look? They would be different forests.

The earthworm forest is simpler. It is quieter. It is more sparse. The main difference that we usually see is once earthworms are in a system, they start consuming the organic matter that sits on the forest floor. And you have a much more barren soil. And so we tend to see herbaceous species having trouble regenerating there. Seedlings struggle.

So you have a lower abundance of vegetation and a lower diversity. For more CBC podcasts, go to cbc.ca.ca slash podcasts. Hi, I'm Jamie Poisson, host of the Daily News Podcast, Frontburner. I got this really cool note from a listener the other day. They wrote, I find myself torn between the desire to understand the world around me and the anxiety associated with the easily access barrage of terrible news. And yet, amidst the torrent, there lies a sweet spot called Front Burner. This is exactly why we make the show.

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