A MARTÍNEZ, HOST:
Parts of the U.S. and Canada are dealing with hordes of slimy intruders - earthworms.
MALTE JOCHUM: Basically, whatever you have been used to, whatever you evolved with for the last few thousands of years, will now change.
LEILA FADEL, HOST:
That's Malte Jochum. He's a soil ecologist from Leipzig University in Germany and one of the authors of a new study about the impact of invasive earthworms on North American forests.
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UNIDENTIFIED CHORUS: (Singing) Doo, doo, doo, doo, doo, doo, doo. Doo, doo, doo, doo, doo, doo, doo.
MARTÍNEZ: Think of worms as nature's happy little workers. They munch on fallen leaves and other vegetation and release nutrients into the soil. But worms from other lands are taking over forests in parts of the U.S. and Canada.
BRUCE SNYDER: There are a whole suite of earthworms that have been invading for the past several hundred years.
FADEL: Bruce Snyder teaches biology at Georgia College & State University, and he says worms from Europe and Asia hitchhiked to America with tourists, livestock, even leftover fishing bait. And once they find their way into a forest, they eat everything.
SNYDER: They're basically removing the whole forest floor. They're eating all the leaf litter, all the partially decomposed litter. And that can drastically change a system.
MARTÍNEZ: The worms are so ravenous they destroy the ground cover that insects rely on. And as insects fade away, all kinds of plants and animals are at risk.
SNYDER: Changing one aspect of the system almost always changes other aspects. That's one of the reasons this recent study is really concerning - is, you know, it's not just the insects; it's - everything in that system is being impacted.
FADEL: Jochum has tips for people who want to help contain the spread of malicious earthworms.
JOCHUM: If you take your bike or you go for a hiking trip in remote areas, clean your tires and boots before you go, and never leave unused fishing bait anywhere. Just take it back home.
MARTÍNEZ: Remember; only you can stop good earthworms from inching toward the dark side. Transcript provided by NPR, Copyright NPR.