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Invasive snake worms make their presence felt in region

  • The Asian jumping worm -- sometimes referred to as a snake worm -- pose a threat to the forest, particularly maple trees, because they eat leaf litter and their castings are not very good for the soil. (University of Wisconsin-Madison photograph) Susan Day

  • While a PhD candidate at Dartmouth College, Justin Richardson does worm research on Vermont's Mount Mansfield in Aug. 2012. Richardson currently works as an assistant professor at the University of Massachusetts Amherst. (Courtesy Justin Richardson)


Combined sources
Tuesday, April 24, 2018

Beware: crazy snake worms may be headed our way.

Researchers say when it comes to invasive earthworms, a particularly nasty annelid species poses a growing threat to a large chunk of New England’s forest ecosystem, including sugar maples.

Crazy snake worms, an Asian invasive prized by fishermen for their aggressive wriggling, first came to the attention of Justin Richardson in 2011, when he began working on a doctorate at Dartmouth College.

Richardson, an assistant professor at the University of Massachusetts Amherst, has fond memories of the field and lab work he used to fuel his dissertation. He’d visit locations such as the Montshire Museum in Norwich, Vt., and use a spade to dig up worms from the black, spongy “organic hemic horizon” that lies just beneath the leaf litter in a healthy forest.

After each worm safari, Richardson popped some of his squirming captives into an “acid worm stew,” using a mass spectrometer to tease out how much gasoline-produced lead had accumulated in their bodies. Others, he freeze-dried and ground into tiny pieces, which he then incinerated. The ash and fumes yielded up data on levels of mercury, which enters the ecosystem by way of coal-burning plants in places like Ohio.

The worms, also called Asian jumping worms, store large amounts of both lead and mercury in their bodies, Richardson’s work showed.

The snake worms can be seen at the UMass campus, but while they exist around Hampshire County, said Richardson, a 2015 study showed they hadn’t been found in Franklin County — yet.

The worms have a characteristic way of disturbing the soil — unlike the Canadian night crawler or other European worms — create a “very light, fluffy-looking layer” and alter the shape of the soil with a grainy material left on top.

The worms ingest the heavy metals as they gobble up organic material; they then pass the metals up the food chain to predators like red-backed salamanders, robins and the Bicknell’s thrush.

Depleting the forest

The snake worms’ capacity to activate buried heavy metals is just the tip of the iceberg.

The much bigger problem, according to Josef Gorres, a University of Vermont professor and Vermont’s leading snake worm authority, is that the fast-breeding, voracious worms are eating the entire organic hemic horizon in some forests, which has dramatic effects on the local ecosystem.

“Sometimes, if you go hiking, you go up that hill and look left and right and there’s a lush understory. You can hardly walk through because there’s so much vegetation there,” he said. “When you walk through a forest invaded by earthworms, then you’ll see very little understory. … It’s a really huge difference.”

Here’s why: Unlike European earthworms, snake worms produce castings that are granular, like coarsely ground coffee.

The worms change how elements cycle in soil and eat the soil, including lead from gasoline and mercury from combustion of coal, said Richardson, who believes the crazy snake worm “could be the ‘smoking gun’ for high concentration of metals found in ground-foraging birds … with high concentrations of mercury and lead in the blood and feathers.”

He’s about to publish a paper examining the impact of the crazy worm on sugar maple seedlings and two other plant species — the Christmas fern, so named for its capacity to remain green into the holiday season, and false Solomon seal, a common native forest plant with white flowers.

The fern, which is good at tapping nutrients from deeper minerals, did just fine in snake worm-heavy areas, but false Solomon seal and sugar maple, which rely almost entirely on the organic material for their nutrients, suffered.

“Sugar maples rely on the forest floor for germination, and as the worms move in, they use forest floor for food and mix it into the soil. That destroys germination bed for sugar maples, and it’s also their nutrient source.”

Gorres says the worms are directly responsible for reducing the understory by 50 or 60 percent. Grazers like deer take what’s left, leaving behind only a few inedible species, like Jack in the pulpit.

“If deer come through and see nothing but sugar maple saplings because everything else is gone, that’s what they eat,” Gorres said.

Though many say the early bird gets the worm, an environmental cascading effect triggers what Gorres calls “early worm’s revenge.”

The elimination of a forest understory leaves little or no cover for ground-nesting birds, such as the Eastern whip-poor-will and the common nighthawk, leaving the calorie-laden eggs of those species vulnerable to predation.

Green thumbs

Worms aerate and churn the soil, which helps gardeners.

“They increase filtration, so that means the soil can store more water,” Gorres said. “There’s good reasons why gardeners like them.”

But gardening’s dirty little secret is that the same worms that help bring in a bumper crop of tomatoes might wreak havoc on neighboring woodlands.

Asian jumping worms were first identified in the country in 1937, and have since been documented throughout New England.

Snake worms can spread on their own — they wiggle a little deeper into the woods each year — but, like so many invasive species, their travel plans get turbo-charged by human intervention.

Every time compost is transported, there’s a good chance of some worm passengers coming along for the ride.

Richardson added, “With the spread of commercial fishing and the importation of worms for agriculture, we’re seeing them being introduced to other areas, including residential areas, and nature preserves. We’re seeing they’re really changing how the elements and nutrients in soil and pollutant metals cycle in soil. We’re now putting those pieces together.”

Gorres recommends New Englanders slow the spread of crazy snake worms by crafting forest management plans that minimize exposure, eliminating fishing bait refuse, limiting the movement of horticultural materials and inspecting all nursery plants for signs of the worm before planting.

The Valley News contributed to this report.