Advertisement

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Climate Change

Are invading earthworms spurring global warming?

Earthworms may unleash billions of metric tons of carbon from northern boreal forests

by Katherine Bourzac
January 3, 2020 | A version of this story appeared in Volume 98, Issue 1

 

Photo of an earthworm on the ground.
Credit: Clark Ukidu/Shutterstock
Dendrobaena earthworms are invading the boreal forests of northern Canada.

Invasive earthworms are spreading into the northern forests of Canada and the US, disturbing the soil and transforming ecosystems, researchers reported at the American Geophysical Union Fall Meeting in San Francisco in December. This “global worming” could contribute to climate change by potentially unleashing the large stocks of carbon stored in northern soils.

The boreal forests—large expanses of wild lands in the planet’s northern latitudes—are Earth’s largest terrestrial carbon sink. Their soils hold an estimated 200 billion metric tons (t) of carbon, 60 billion t of it in Canada alone.

Until about 20 years ago, scientists didn’t think it was possible for earthworms to survive in the relatively cold, acidic soils of the Canadian boreal forests. But these days researchers find the worms just about everywhere they look, says Justine Lejoly, a researcher in the lab of University of Alberta soil biogeochemist Sylvie Quideau. People spread the critters when they use them as live fishing bait or to help improve soil for farming and gardening. As the northern latitudes have warmed, earthworms’ habitable range has expanded.

Earthworms can loosen the soil and spur nutrient cycling between the soil and plants. Earthworms in the boreal forests of North America have the potential to unleash a “carbon release on the scale of wildfires,” Lejoly says.

Earthworm invasions occur over the course of decades—which makes them difficult to study in the lab. So the University of Alberta team visited three boreal forest field sites in the province and did a deep dive into the soil chemistry to determine how the worms were affecting carbon storage.

Lejoly presented the team’s preliminary results at the AGU meeting. At some of the sites, she says, “the forest floor almost disappeared.” Before the invasion, the top layer of soil at the Alberta sites stored about 30 t of carbon per hectare; after, they held just 2 t per hectare. The implications for the underlying mineral soil are less clear. The carbon was still there, but it was stored in a less stable form. The clumps in the soil were smaller, which means it will probably release carbon more readily as temperatures increase, Lejoly says.

Kyungsoo Yoo, a soil biogeochemist at the University of Minnesota, says worm-triggered changes can cascade through forest ecosystems in unexpected ways. It’s possible that later stages of an invasion will put carbon back into the soil, as the worms burrow in deeper and leave their droppings behind. However, the invading worms can also have wide-ranging and negative effects on the forest ecosystem that in turn lead to the release of carbon. Clearing off the forest floor can make sugar maple seedlings more visible to snacking deer, for example. In New England and the Great Lakes region, Yoo says, invading earthworms have changed the soil microbiome from fungal to bacterial dominance. This shift causes a disadvantage for plants that live in symbiosis with fungi, exchanging sugars for other nutrients through their roots.

Earthworm invasions and their ecological consequences are “an example of what humans can do without even knowing it,” Yoo says.

Article:

This article has been sent to the following recipient:

0 /1 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.