The world’s boreal forests have been largely earthworm-free since the last Ice Age. But as invaders arrive and burrow into the leaf litter, they free up carbon and may accelerate climate change.
Credit: Cristina Gonzalez Sevilleja

Cindy Shaw, a carbon-research scientist with the Canadian Forest Service, studies the boreal forest — the world’s most northerly forest, which circles the top of the globe like a ring of hair around a balding head.

A few years ago, while conducting a study in northern Alberta to see how the forest floor was recovering after oil and gas activity, she saw something she had never seen there before: earthworms.

“I was amazed,” she said. “At the very first plot, there was a lot of evidence of earthworm activity.”

Native earthworms disappeared from most of northern North America 10,000 years ago, during the ice age. Now invasive earthworm species from southern Europe — survivors of that frozen epoch, and introduced to this continent by European settlers centuries ago — are making their way through […]

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