Vanishing North

An invasion threatens a ghostly fern in the Minnesota woods

A weird ambassador to the underground meets a toothless, deadly predator.

By Jennifer Bjorhus Star Tribune

Photos by Brian Peterson Star Tribune

FOURTH IN A SERIES • October 14, 2022

An invasion threatens a ghostly fern in the Minnesota woods

Vanishing North

A weird ambassador to the underground meets a toothless, deadly predator.

By Jennifer Bjorhus Star Tribune

Photos by Brian Peterson Star Tribune

FOURTH IN A SERIES • October 14, 2022

Covered in bug repellent and netting, three forest stewards picked their way through a dark and remote part of Chippewa National Forest.

The July air was moist and thick with mosquitoes and biting flies. The group stepped through the lush undergrowth and over mossy logs, crossing the mat of rotting leaves and twigs that form the forest floor.

They were hunting the goblin fern. Ancient and otherworldly, the goblin fern spends most of its life underground. When it does come up every few years, the strange plant sends up a tiny leaf with a spore-bearing stalk that's nearly impossible to see, even on hands and knees.

The Leech Lake Band of Ojibwe, the tribe whose reservation is mostly inside the national forest, has studied the imperiled fern for years, along with academic and government researchers. Only four decades after scientists first documented the species, researchers now fear it could vanish in the next ten years.

In the search party that day were Kate Hagsten, plants director with the Leech Lake Band's resource management division; Raining White, invasive species specialist with the tribe; and botanist Bobby Henderson. The spongy forest carpet was so rich it felt like walking on a mattress.

Finally, they spotted one. One goblin fern and then another — minuscule, bright green fists poking up, no more than an inch or two high.

These ferns look nothing like the backyard variety with their big, airy fronds. These miniature plants appear misshapen and somehow unfinished, although they are exactly as they should be and perfectly calibrated to their dark forest ecosystem. They have lived there for thousands of years, as far as anyone knows.

This is how the forest is supposed to be.

The worms aren't here yet.

Hagsten, White and Henderson gathered around the fern and sought to explain its importance. It's about the web of life, White finally said.

"It kind of opened up my mind," he said. "It indicates the maples are healthy, which is an important resource for the Leech Lake community."

Without the goblin fern, Hagsten said, "everything else disappears too."

Brian Peterson, Star Tribune
Raining White, invasive species specialist with the Leech Lake Band of Ojibwe, above, said goblin ferns hold a key spot in the web of life that supports maple trees, integral to Ojibwe life.

As tiny as it is, the fern is attached to a vast underground fungal network that forms the soil foundation of the forest and supports the maple-basswood stands that are central to Ojibwe traditions. Each spring, when the night temperatures still drop below freezing but days are warming, families have joined at sugar camps to tap the maple trees and boil the sap into syrup — still a dietary staple and one of the first foods that some Ojibwe parents feed their infants.

The goblin fern is a moonwort, a global group of ancient ferns that predate the dinosaurs and enjoy a distinct following among plant enthusiasts. Botrychium mormo was first documented in Minnesota and Michigan by the late botanists W.H. Wagner Jr. and his wife, Florence S. Wagner, in a 1981 article in the American Fern Journal.

"The goblinish appearance and behavior of this odd plant has inspired the English name of Little Goblin," the Wagners wrote.

Goblin ferns have been found in Wisconsin, Michigan, Ontario and Quebec — but Minnesota is its stronghold. Chippewa National Forest is home to most of the world's population, according to the Leech Lake Band, although no one knew that when the Ojibwe homelands were designated as a national forest in 1908.

Most people probably know the national forest as one of the country's largest breeding grounds for bald eagles. The goblin fern is the opposite of the majestic predator. Behaving like a mushroom, the cryptic plant depends on fungi for its survival. These fungi extend below ground through the forest in a vast network of long, slender filaments called hyphae (HY-fee).

The roots of trees and other plants join with the hyphae to get most of their moisture and nutrients. The fungi, in turn, feed on sugar and carbohydrates created by the trees and plants through photosynthesis. The goblin fern joins in and poaches on the process for food, said Minnesota state botanist Welby Smith. It's a classic move in nature, he said, one that orchids do all the time.

The goblin fern can stay underground for years before poking up through the forest floor to reproduce by spreading spores. No one knows what cues the fern's internal clock to do this.

Nearly as soon as it was found, the fern was declared to be in trouble. In 1984, the state Department of Natural Resources (DNR) listed the goblin fern as a "special concern" species, pointing to logging and the loss of northern Minnesota's old-growth forest habitat as the primary threat.

Then, in the late 1990s, scientists in Minnesota discovered a new and even more sinister threat to the goblin fern — and almost everything around it. Something was destroying the forest floor.

Leaving the goblin ferns behind, Hagsten and White hiked out to their pickup. They drove to a different part of the forest and parked on the side of a busy road, not far from a resort and some boat launches, and waded through the ditch into the trees.

Here was all hard ground. There was a lot of Pennsylvania sedge growing — one plant that doesn't need underground fungi. Some of the trees had what resembled high water marks on their lower trunks. That's where the forest floor used to be, White noted. The recession has left the trees a little less anchored, more prone to blowdowns. Water runs off the compacted soil that more easily erodes.

The forest litter doesn't break down and rot as it should. Hagsten pointed to downed trees "that aren't doing anything," and probably look as fresh as when they fell. The changed soil stunts the growth of maple trees and shortens their lives.

This part of the forest had been wormed.

Non-native earthworms have invaded Minnesota's northern forests in a slow-moving advance that endangers not just the Chippewa National Forest but all hardwood forests across the region.

The worms are "re-engineering all the functions of the ecosystem," said Lee Frelich, director of the University of Minnesota's Center for Forest Ecology.

Brian Peterson, Star Tribune
Invasive earthworms, which are not native to Minnesota, are destroying forest floors across the state. Here, an earthworm stretches on the ground in a heavily wormed and damaged section of Chippewa National Forest.

They devour all three layers of organic matter on the forest floor, rich and full of microbes: the forest litter on top, the layer below of decomposing leaves and twigs and logs called duff, and the decomposed matter below called humus. Then they go underground and eat the fungi on the tree roots.

The forest was unprepared for the onslaught.

Minnesota has no native earthworms. That's counterintuitive to people conditioned to see them as an indicator of healthy soil. But earthworms did not survive the glaciers that molded the state, so Minnesota's forests evolved without them. Minnesota has other types of native worms, but they're smaller and not voracious.

Scientists say the earthworms likely arrived in the soil dumped in ship ballasts and pots of plants with European settlers and, more recently, in fish bait. There are more than a dozen earthworm species now in the state. One of the worst is the nightcrawler, Lumbricus terrestris, a favorite with anglers.

For something so slow and toothless, the worms do an astonishing amount of damage to forests. They are eyeless eating machines, consuming up to half their body weight each day, said Ryan Hueffmeier, an earthworm researcher and director of Boulder Lake Environmental Learning Center north of Duluth who maintains the Great Lakes Worm Watch website.

And they are nearly everywhere in Minnesota now, except for a few spots such as the ridge along the North Shore, Frelich said. They're even in the Boundary Waters Canoe Area Wilderness, although Frelich estimated it's only about 30% to 40% infested, radiating from the most popular routes.

Earthworms leave behind tell-tale piles of dark castings on the ground's surface.

"Basically anywhere you're stepping, you're stepping on earthworm poop," Hueffmeier said.

Under state law it is illegal to release invasive species into the wild. But earthworms? They are all but unregulated. Anglers regularly toss leftover bait on the ground, and earthworms have been propelled great distances across the state by the tires on unwashed cars, pickups, logging equipment and ATVs. Worm invasions can be traced to proximity to cabins, roads, boat launches and ATV trails.

"You can see the decline of biodiversity the closer you get to the ATV trails," said Hagsten. "It's very obvious."

"I cringe because I remember being a kid and just throwing my worms," said White. "They're good bait."

News of the powerful new threat to the goblin fern prompted some conservation efforts. By 2004, Chippewa National Forest set 250-foot buffers around goblin fern spots to prevent logging and other activities, and declared the adjacent areas must have at least a 70% tree canopy.

The tribe would prefer 500 feet, Hagsten said, but its powers are limited. The national forest is a patchwork of ownership, and the Leech Lake Band owns only about 5% or so of its reservation land. The U.S. Forest Service owns about 40% of the national forest, the single largest chunk and the land where most of the goblin ferns are. The state owns about 17% and has also required buffers around goblin ferns.

Brian Peterson, Star Tribune
Organic matter on the ground doesn't decay like it should in heavily-wormed forest, such as the section of Chippewa National Forest that Kate Hagsten, plants director with the Leech Lake Band's resource management division, above, walks through.

For years, federal, state and tribal resource managers have tried to educate people to dump unused live bait in the trash, not on the ground or in the lake where the bait can survive. Yellowstone National Park has banned live bait. But Chippewa National Forest has not. The DNR said live bait is "foundational" to anglers in Minnesota and a ban would be "incredibly difficult."

The Leech Lake Band has listed the goblin fern as endangered, Minnesota upgraded it to threatened and the local region of the U.S. Forest Service deemed it a "regional forester sensitive species."

None of the efforts have stopped the plant's rapid decline. Looking around the heavily wormed stand, Hagsten and White said they aren't sure what to do next.

Hagsten was frustrated. For years she gave talks, held workshops and delivered presentations to fishing groups and bored high schoolers. Little changed. Maybe she could target gardeners, she mused.

They toyed with the idea of controlled burns to starve out the earthworms, or even putting a bounty on them, paying people to dump a mustard slurry on the ground to bring them to the surface and collect buckets of them. But what good would that do given the scale of the problem?

"It's kind of one of the sadder stories on the landscape," Hagsten lamented.

She said she's working to get the goblin fern listed under the federal Endangered Species Act. That would trigger the creation of a recovery plan for the species that requires all the different governments in the forest to work together much more closely.

Meanwhile, the Leech Lake Band is fighting to protect what remains of the goblin fern's old-growth habitat, opposing the large mill that North Carolina-based Huber Engineered Woods wants to build in nearby Cohasset. The mill would consume about 400,000 cords of wood a year to make oriented strand board used for constructing buildings, mostly from aspen trees.

"The Huber Project will hasten the decline of goblin fern by perpetuating short-term aspen regeneration that does not allow forest succession and increased logging disturbance that hasten earthworm spread," the band said in its objection letter to the city of Cohasset earlier this year. The goblin fern is declining so rapidly, it will likely be extinct "within a decade or so," it said.

The band filed an appeal at the state Court of Appeals, arguing the city should have ordered an in-depth environmental review — the kind that would carefully consider the species struggling to survive in a changing Chippewa National Forest.

Sometime before Minnesota's winter sets in, after the huge bald eagles that sweep the Chippewa's treetops have raised their young, the ferns that Hagsten, White and Henderson hiked to in July will disappear. The trees will shed their leaves, and the ferns will retreat below ground again to mingle with the fungi as the earthworms inch ever closer.

Above ground, moonwort admirers will wait in hope that nature's unknown signal will keep telling the odd little plant that it is time, again, to come out.

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