Poop From Invasive 'Crazy Worms' Is Altering Midwest Soil

Scientists found that the poop-balls produced by invasive Asian jumping worms are packed with nutrients that can’t be easily accessed by plants native to the Midwest US.

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Nov 7 2018, 1:21pm

Everybody poops, and sometimes that poop can help enrich and fertilize ecosystems. But new research suggests that feces from Asian jumping worms, an invasive group of earthworms that’s been inching into the US Midwest in recent years, may be negatively affecting habitats.

Jenelle Wempner, a geoscientist at the University of Wisconsin in Madison, studied the worms’ voluminous production of poop-balls—called “aggregates”—and found that they may be eroding and leaching nutrients from soil. Wempner will be presenting her research at the annual meeting of the Geological Society of America in Indianapolis on Wednesday.

“The way that these worms change the soil is something new,” she said in a statement. “You can see very clearly that they have been there. They leave little balls of soil. Imagine a soil surface covered with coffee grounds.”

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Asian jumping worm aggregates. Image: The Geological Society of America

Asian jumping worms—also known as crazy worms, Alabama jumpers, and snake worms—are native to Southeast Asia, but were accidentally introduced to the southeast United States in the 19th century. Over the decades, they have migrated north and west, and were first detected in Wisconsin in 2013.

In contrast to their European earthworm cousins, which burrow inches deep in forest soil, Asian jumping worms like to stay close to the surface to feed on the “litter layer” composed of dead leaves and twigs. Previous studies suggested that the worms ravenously consume this leaf litter, removing nutrients and locking them up in their coffee ground aggregates where germinating plants can’t easily access them.

Wempner was able to corroborate that finding by examining aggregates under a scanning electron microscope. Her team found high levels of iron, aluminum, potassium, and calcium in the poop-balls, confirming that the worms are decreasing the availability of key nutrients in their ecosystems and increasing the likelihood of soil erosion.

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"Increased erosion would degrade soil health," Wempner told me in an email. "It would change water flow and retention patterns. The worms are mostly an issue in the sense that they lock away nutrients from plants in these aggregates. A trophic cascade may occur if plants don't receive these nutrients, the animals that eat those plants no longer have nutrition, etc."

Since these invasive worms are relatively new to the Midwest, more research will be needed to predict their large-scale effect on regional habitats. But some pest control techniques have already been recommended to curb their populations. Wempner’s team suggests chemical treatments tailored to the species’ cocoons, while a separate 2015 study proposed using controlled ground fires to manage the worms.

The presence of the worms is another example of the unpredictable consequences of introducing invasive species to new biomes. These worms may take small poops, but in aggregate, they play a big role in the ecosystem.

"These worms are an invasive species everywhere outside of their native habitats," Wempner said "The impacts their invasion will have in the future are relatively unexplored."

Update: This article has been updated to include comments from Jenelle Wempner, the author of the featured study.

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