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Here's some scandalous environmental dirt: Earthworms are actually the bad guys.

Yes, those wriggly, underground eating machines are still good for anglers seeking plump and juicy bait and gardeners who dig rich and fertile soil. But they are also now vilified by ecologists as an unwanted, alien invader in our forests.

Really.

"It's OK to chuckle. I know it sounds weird, even to biologists and ecologists -- but probably especially to the average person," said Cindy Hale, a forest ecologist and researcher from the University of Minnesota at Duluth. Hale has studied the detrimental effects of worms on forest ecosystems around the Great Lakes for the last 13 years.

Hale lectured scientists and the public about the still little-understood and newly researched underground threat at a soil symposium Sept. 11 at the Cleveland Museum of Natural History.

"And it's not that earthworms are all bad all the time and in every place," she told more than 150 listeners -- many of who said they had never heard anyone challenge the "myth that worms are good for all soils," she said.

"They're just bad for our forests, and forests are very important for us as human beings -- physically, emotionally, even spiritually."

Worms vs. sugar maples

In fact, it is the lowly earthworms that are now considered the invasive species responsible for what Hale and other researchers are calling "Forest Decline Syndrome" in North America.

Earthworms -- specifically their waste as it replaces the soil -- are threatening most directly the economically important sugar maple tree as they slowly alter the makeup of the great northern forests of the United States and Canada, Hale said.

"You take earthworms and put them in a sugar maple forest that evolved for 10,000 years in the complete absence of worms and they can have very negative consequences," she said.

Hale hosts the Great Lakes Worm Watch Web site (greatlakeswormwatch.org) and for 13 years has studied what she calls a "cascade of changes in hardwood forest ecosystems" caused by several common worm species.

"They change the way that the organic matter breaks down, which changes the chemical makeup and structure of the soil," she said. "And that affects growth of the tree seedlings and the rest of the understory plant community in that forest -- and eventually the sugar maples."

That's where the worm scourge could hit Northeast Ohio -- as well as certain maple-producing areas in Canada, Vermont, Maine and Wisconsin -- in the pocketbook.

Maple sugaring is big business here and part of a regional identity. But climate scientists have already said that the maple tree may be slowly being pushed north by warming temperatures.

Now biologists say worms are threatening maple trees from the ground up.

While there is no reported evidence of maple tree die-off, studies in Minnesota and Wisconsin have suggested that, at the very least, sugar maple saplings are not taking root in soils that have been worked over by earthworms -- meaning that the next generation of maples is at risk.

Invaders taking over

And that is what makes the once seemingly benign earthworm -- 16 harmful species have been tagged in the Great Lakes region -- an unwelcome interloper.

Think of them as slow-moving brethren to the zebra and quagga mussels causing problems in Lake Erie or plants like garlic mustard or purple loosestrife choking out native species in our bogs, ditches and fields.

"I had no idea that they were bad. I was taught they were wonderful," said Jim Bissell, curator of botany and natural-areas coordinator for the Cleveland Museum of Natural History. "But the soil of any ecosystem is the basis for its life, and if it changes -- the whole ecosystem follows."

More than 100 species of earthworms are found throughout much of the rest of the United States and were once native to the Great Lakes region, Hale said. But the creeping onset of giant glaciers from the north wiped out virtually all terrestrial life, including earthworms.

That means that all the great northern forests -- from Canada down through Michigan, Wisconsin and Minnesota and into Ohio -- developed over thousands of years as worm-free ecosystems.

(The worms that survived the last ice age in the Central and Southern United States still haven't had enough time to crawl this far north. At 5 yards a year, they could have traveled just over 30 miles in the last 11,000 years, scientists estimate.)

So when European settlers unknowingly brought earthworms into the New World about 250 years ago, along with plants and probably in ship ballast, the creepy-crawly invertebrates slowly began their work on a new continent.

Worm waste vs. leaf cover

The job of an earthworm is primarily to take in food -- leaves and other decaying plant and animal material on the ground -- and squeeze out its waste.

That's the darkly rich stuff prized by gardeners -- soil that is nutrient-rich and more porous than dense, mineral-based soil in many areas. But that same earthworm waste is actually less porous -- more dense -- than and harmful to a forest floor made up of rotting vegetation.

"And they do what they do very well -- there is definitely a beneficial side to earthworms, but not for our forests," said Hale, who conducted a worm survey earlier this month with 15 other biologists, naturalists and others in Grand River Terraces, a 745-acre preserve in Ashtabula County. The field trip was part of the soil symposium from Sept. 10-12 at the museum.

The group poured water laced with mustard powder into the soil to irritate worms and draw them to the surface to be counted and categorized, while Hale taught local scientists how to identify worm-infested areas.

"There's one -- and there's another," said museum Biodiversity Coordinator David Kriska, wielding a pair of tweezers to yank the bothered worms the rest of the way out of the ground. "These are the ones we're talking about that are causing all the issues."

The problem is that when worms come to your forest, they slowly chew up and spew out the rotting -- but life-sustaining -- layers of leaves covering the forest floor.

While the worms do provide food for some animals, many other animals, like ground-nesting birds, small mammals, amphibians, reptiles, insects and spiders, lose their primary habitat when the worms consume all the ground cover.

Worse, some studies suggest that once the forest floor is cleared, it can become a more welcome home for the invasive plants like garlic mustard, Hale said. Other research suggests that the there is a multiplying effect on forest devastation when earthworms first remove the ground cover and then deer eat the seedlings, saplings and other understory plants.

What we can do

Even so, the damage inflicted by a million earthworms would likely be limited to where they were first dropped -- expanding ever so slowly if it weren't for human help.

But humans continue to do most of the worm moving -- by the dumping of bait, by all-terrain vehicles or by vermicomposting, the practice of using worms to help break down vegetation for our gardens.

Brian Parsons, director of conservation at Holden Arboretum, said that researchers and planners at the site -- a 3,600-acre collection of trees and plants in Lake and Geauga counties that is among the largest in the nation -- are also responding to the earthworm nuisance.

"We're not only starting to do more research in the woodlands, which includes what is going on underground, but we're also changing the way we might site a new garden and posting 'No Dumping Bait' signs near our ponds," Parsons said. "That's really about all that can be done at this point -- short of building a sulfur moat around Holden."

Which leads Hale to her final point in spreading the new gospel of worm awareness -- let's try to slow the slimy invaders down a bit more.

"Really, it's like any other invasive species -- try not to move them around the region," Hale said. "And the beauty of that, unlike with other fast-moving invasives, is that we could buy ourselves a few hundred years time.

"Worms are a problem, sure, but they really don't move very fast, you know?"