I don’t remember how we started talking about earthworms. I guess it wasn’t unlikely—Annise is a charismatic, conversational young adult who is deeply engaged in her post-doctorate research on earthworms. Her profile in the Cornell Department of Natural Resources says: “Native and nonnative threats to forest plant communities; invasive earthworm dynamics; restoration ecology.” So I suppose that’s how we started talking about it.
In any case, I only pulled out the audio recorder after I decided it was too fascinating a perspective to not share, so what I have left from the conversation jumps right into the interplay between earthworm and salamander populations.
She explained that salamanders live in the duff layer of the forest soil, a layer of decomposed organic material in between the forest litter and mineral soil. “Earthworms start decomposing all of the duff and changing the habitat, so you kind of just have this bare minimum soil, instead of this duff. It’s like instead of the mattress up there, you’ve got your freshman-year dorm single mattress,” she laughed, “like really homogenous, not like those layers of pillow top and memory foam.”
I know that’s kind of a strange place to start but it’s a useful beginning because it demonstrates Annise’s unique ability to communicate high-level ecological science in a really interesting and story-based way. I only knew marginally about salamanders and didn’t know much about earthworms. She got me on board.
Earthworms’ activity in the soil causes habitat loss and disrupts the temperature regulation of the duff. “Salamanders are really attuned to that,” she said, “the temperature of the soil, the moisture of the soil.”
“You can go out anywhere. The more earthworms you have, the fewer salamanders you have.”
Annise told me that the salamanders have the biggest biomass in the mixed hardwood forest, which means that the combined mass of all the salamanders in the forest is greater than that of any other animal or insect. “They’re important trophic connectors,” she added. “Lots of things eat them and they eat lots of things.” The invasion of earthworms into forest ecosystems is a change that is happening before our eyes, so the consequences aren’t fully known yet. That there will be consequences, however, is a given. Earthworms are destabilizing the population of the biggest biomass in the forest.
I guess I should mention that earthworms are not native to North America. They arrived with European migration in the 1600s. They’re different from other invasive species, however, because their invasion is a slow burn.
“With a lot of invasive species, you’re worried about them showing up and then migrating really quickly or setting big seed sets or something like that. Earthworms, for the most part, are moving really slowly. The European species have been here spreading slowly for a while, and I think that that is sort of the new reality.” According to Annise, they weren’t in all forests and their presence was significantly connected to fishing areas. Fishermen often throw away leftover bait, which then survive and establish themselves in the local ecosystem.
It’s not bad, though. It’s worse.
“There’s a new family of earthworms coming over from Asia,” she continued, “and they can get to really high densities. They basically transform any soil into gravelly castings, so nothing can survive in it. And they’re pretty new. They’re really bad for farms, too, for flowerbeds. So I think that this one has the potential to be more important for people.”
Combating invasive species is a tough and often a losing game. Invasive species are invasive because they have an unprecedented advantage in the local ecosystem, and human attempts to fight that advantage are relatively small in the scope of ecological interconnection. Annise pointed out, however, that human actions in causing or exacerbating the presence of invasive species are often quite large. “A lot of invasive species management is misguided,” she began. “I think it’s kind of driven more by human psychology, that we love to see a pile this pile of invasive species that we pulled out with our own hands, and we did all this work that there’s a pile to show how much work we did, to see how much we accomplished.”
“But it’s a little bit harder and maybe more depressing to look at the actual consequences for the native species. For a lot of invasive plants it seems to be that they are quite often more like, not the drivers for the change but kind of along for the ride. We did something else to that forest, we clear-cut it or did something else, and then the invasive species came in. People point to them for being the culprits but it seems that maybe they are just a consequence for something else. It’s easier to blame on invasive species than to change the way we manage things.”
The audio got messy with other conversations in the background, but Annise was also insightful about the nuances between earthworms effects on different ecosystems.
“Not all soil is the same,” she said. “Not all plants growing in the soil need the same things. So what we’re doing is we’re taking this idea of farm fields, where earthworms are good—they do aerate the soil because it gets tilled up and it doesn’t have the same aggregation that the forests have. There’s many reasons that a forest and a field are different. The fields get plowed, the forests don’t get plowed, they get decomposed by fungi and bacteria. That’s one thing. Then the plants that you’re putting into a field are different from the plants in a forest. Plants in fields have been exposed to earthworms for a really long time, we’ve bred them to grow into plowed soil, but the forest plants have evolved to grow into non-plowed soil. In fields we apply fertilizer and herbicides and things like that, but in the forests plants rely on their connection to mycorrhizae to get a lot of the nutrients. And earthworms are really bad for mycorrhizae, they eat them and they stir things up so it’s really hard for a big hyphal network to establish. So the way that plants get nutrients is different in fields versus forests.”
This comparison came because I had asked why everyone thought earthworms were good.
“We’ve created this artificial habitat in a field where worms are really good. So that’s not wrong. But forests just function really differently. That’s where earthworms are changing the conditions.”
The perception of earthworms as wholly good began when Darwin wrote about them in 1881. “All of a sudden they were these like, angels of the soil that could do no wrong.” Annise paused. “I think there’s a message there, that you can’t think of an ecological player as just good or just bad. It’s going to be good for some things and bad for some things.”
Getting people to recognize that, however, poses challenges because making change is hard. There’s a lack of cultural awareness about earthworms and about invasive species in general, and there’s apathy towards changing behaviours that exacerbate them. Annise was hopeful nonetheless.
“It’s in people’s heads, they really do care about earthworms one way or the other, so being able to capitalize on that. They know that earthworms do a lot already, so maybe it’s not that much of a leap to realize that earthworms do a lot of bad stuff.”
Annie and I did talk almost exclusively about earthworms, and I think that ecology and invasive species are an important topic to bring to the forefront. I will also mention, however, that Annise is part of Femina Sci, a collective of women scientists whose mission is to create an online community that promotes the empowerment of women in science. Their blog contains personal essays and panels about their work and other topics, and their website links to a dozen resources related to women in STEM fields
I’ve probably written more about earthworms than I expected I would in the context of this project, but as I said already I think it relates to important topics. Our responses to forest management, to invasive species, to scientists and woman leaders are all important, perhaps now more than ever.
You can learn more about stopping the spread of invasive species in Ontario on the provincial government website, and follow @FeminaSci on Twitter for more updates on women in science.