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Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things


Wild Things

Invasive earthworms may be taking a toll on sugar maples

earthworm

Earthworms are good for soil — when the ecosystem has evolved with the worms. Where worms are newcomers, though, such as in Upper Great Lakes groves of sugar maples, the invaders can cause problems.

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Earthworms are great for soil, right? Well, not always. In places where there have been no earthworms for thousands of years, foreign worms can wreak havoc on soils. And that can cause a cascade of problems throughout an area’s food web. Now comes evidence that invader worms in the Upper Great Lakes may be stressing the region’s sugar maples.

There are native earthworms in North America, but not in regions that had been covered in glaciers during the Ice Age. Once the ice melted, living things returned. Earthworms don’t move that quickly, though, and even after 10,000 years, they’ve only made small inroads into the north on their own.

But people have inadvertently intervened. Sometimes they’ve dumped their leftover bait in worm-free zones. Or they’ve accidentally brought worms or eggs in the soil stuck to cars or trucks. And the worms took up residence as far north as Alberta’s boreal forests.

Earthworms “are not really supposed to be in some of these areas,” says Tara Bal, a forest health scientist at Michigan Technological University in Houghton. “In a garden, they’re good,” she notes. They help to mix soil. But that isn’t a good thing in a northern forest where soil is naturally stratified and nutrients tend to be found only in the uppermost layer near the leaf litter. “That’s what the trees have been used to,” Bal says. Those trees include sugar maples, which have shallow roots to get those nutrients. But worms mix up the soils and take away that nutrient-rich layer.

stressed sugar maple Bal didn’t start out studying worms in northern regions. She and her colleagues were brought in to address a problem that sugar maple growers were experiencing. Some of the trees appeared to be stressed out. They were experiencing what’s called dieback, when whole branches die, fall off and regrow. This is worrisome because if enough of the tree dies off, “it’s a slow spiral from there,” Bal says — the whole tree eventually dies.

To investigate, the researchers collected data on trees and anything that could be affecting them, from soil type to slope to insects. They looked at trees in 120 plots in Michigan, Wisconsin and Minnesota. And they compared trees that were on growers’ land with those on public land, thinking that how the trees were managed might have some effect.

When the researchers analyzed the data, “the same thing that kept coming up over and over again was the forest floor condition,” Bal says. “That is directly related to the presence of earthworms.” They didn’t go out to look for the worms, but they could see signs of them in the amount of carbon in the soil and in changes in the ground cover. Wildflowers, for instance, were replaced by grasses and sedges, the researchers report July 26 in Biological Invasions.

Bal and her team can’t say what this means for maple syrup production. It might not mean anything at all. But “worms are ecosystem engineers,” she notes. “They’re changing the food chain.” Everything from insects to birds to salamanders could be affected by the arrival of worms.

Even if the sugar maples take a hit, though, there could be an upside, Bal says. These trees are often grown with few other types of trees around. Such a grove is naturally less resilient to climate change and extreme weather. So replacing some of those sugar maples with other trees could result in a healthier, more resilient forest in the future, Bal says.

Animals

These spiders crossed an ocean to get to Australia

By Sarah Zielinski 9:00am, August 15, 2017
The nearest relatives of an Australian trapdoor spider live in Africa. They crossed the Indian Ocean to get to Australia, a new study suggests.
Animals,, Ecology

One creature’s meal is another’s pain in the butt

By Sarah Zielinski 12:30pm, August 4, 2017
Kelp and dolphin gulls in Patagonia have found a new food source. But they accidentally injure fur seal pups to get it.
Animals

Fire ants build towers with three simple rules

By Sarah Zielinski 2:54pm, July 21, 2017
Fire ants use the same set of simple rules to produce static rafts and perpetually moving towers.
Animals,, Ecology

Drowned wildebeests can feed a river ecosystem for years

By Sarah Zielinski 9:00am, June 27, 2017
Only a small percentage of wildebeests drown as they cross the Mara River, but they provide resources for the river ecosystem for years after their deaths.
Animals

Sooty terns’ migration takes the birds into the path of hurricanes

By Sarah Zielinski 10:35am, June 2, 2017
Sooty terns migrate south from southern Florida and back again. The track sometimes takes the birds into the path of hurricanes, a new study finds.
Animals

Why create a model of mammal defecation? Because everyone poops

By Sarah Zielinski 7:00am, May 11, 2017
Mammals that defecate in the same fashion as humans all excrete waste within the same time frame, no matter their size, a new study finds.
Animals

How a dolphin eats an octopus without dying

By Sarah Zielinski 1:00pm, April 25, 2017
An octopus’s tentacles can kill a dolphin — or a human — when eaten alive. But wily dolphins in Australia have figured out how to do this safely.
Animals,, Conservation

Improbable ‘black swan’ events can devastate animal populations

By Sarah Zielinski 9:00am, April 17, 2017
Conservation managers should take a note from the world of investments and pay attention to “black swan” events, a new study posits.
Animals

Camera trap catches a badger burying a cow

By Sarah Zielinski 11:00am, March 31, 2017
Badgers are known to bury small animals to save them for future eating. Now researchers have caught them caching something much bigger: young cows.
Animals,, Conservation

De-extinction probably isn’t worth it

By Sarah Zielinski 7:00am, March 9, 2017
Diverting money to resurrecting extinct creatures could put those still on Earth at risk.
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