In a clearing at the edge of one of the largest intact forests on Earth, Laura Kavajecz flits about like a tree fairy with a clipboard, slipping long mesh tubes over tiny seedlings. The sun beats down. It’s buggy. The ground is covered with a tangle of downed trunks, stumps and severed limbs. Kavajecz, a graduate student, has a mundane but vital task: Protecting the fledgling trees — 33,000 of them scattered across Minnesota’s northern forest — from the scourge of deer that await in the shadows.
These are no ordinary seedlings. They are red oak, yellow birch and other species common in southern parts of the state, and they are pivotal players in an audacious attempt to thwart climate change along the most vulnerable flank of the boreal forest that sweeps down into Minnesota from Canada.
Planted for a warmer, drier future, the trees are an experiment in hope as much as science.
“It’s the most empowered I’ve felt about climate change since I started despairing over it,” said Meredith Cornett of the Nature Conservancy of Minnesota, which launched the project this year.
There is not much time.
A stark forecast looms for Minnesota’s great North Woods, the mixed hardwood and conifer forest that grew when the glaciers retreated during the last great climate change 12,000 years ago.
Driven by a warming climate, scientists predict, the forest will soon follow the glaciers and retreat north by as much as 300 miles in the next century. Much of northern Minnesota, they say, will become open savannas like those in Nebraska and eastern Kansas — with grasses and brush, a few scattered trees, and domes of bare rock rising from the ground.
For future generations of Minnesotans who love fishing, canoeing and the sight of a moose in the piney North Woods, that cherished outdoors experience is likely to be the stuff of grandparents’ tales.
Gone too, will be the storied creatures — lynx, owls, pine martens — that evolved along with the northern forests. Altogether, the transformation will have enormous impacts on northeast Minnesota, including the wilderness area that draws 250,000 visitors every year and has become a destination of national renown.
But Cornett’s new resolve is shared by many other scientists, landowners and tree lovers who are confronting the inevitability of a warmer world. With planning, research and enough human intervention, they say, Minnesota might hang onto a forest even in the face of a climate that, geologically speaking, is changing at a breathtaking pace.
It won’t be the same North Woods. But, like Laura Kavajecz’s tiny twigs, it’s one that might thrive in the climate of the next century.
That vision is already taking root.
On Lake Superior’s North Shore, landowners are planting different species to replace stands of birch that are dying from drought and disease.
Outside Ely and Cloquet, University of Minnesota scientists are artificially warming 10 species of trees to see which, if any, will survive in the new climate.
In the far western part of the state, a unique remnant of an ancient hardwood forest from a much warmer era is being eyed as priceless genetic stock for the future.
And the white pine, a magnificent conifer that almost disappeared from Minnesota, is being brought back in an experiment that could make it a dominant species in a warmer world.
Still, these kinds of interventions are controversial, says Christian Messier, a forest ecologist at the University of Quebec. Many foresters trust that the forest will take care of its own evolution, as it has for thousands of years. They fear making mistakes that could launch new invasive species or massive insect infestations, Messier said. That debate is especially contentious around protected wilderness such as the Boundary Waters Canoe Area and Isle Royale National Park, where only nature is supposed to rule.
Underlying the debate is the greatest uncertainty of all: What humans will do. At current rates of greenhouse gas emissions, average summer temperatures in northern Minnesota could rise by 8 to 10 degrees Fahrenheit in 100 years. If that happens, scientists say, then probably nothing will save the North Woods.
THE BOREAL FOREST
The boreal forest, which covers 1.4 billion acres across most of Canada, dips down at its southern edge into Minnesota on a diagonal line from Roseau to south of Duluth. This is where a visitor finds the air suddenly sharper and spiced with the smell of pine.
It is the edge of a vast conifer forest and wetland ecosystem — a biome — created by the frigid arctic air mass that circles the top of the globe and provides Minnesota its classic winters. It rivals the world’s rain forests for its value to industry, wildlife, biological diversity, clean air and water, and as a global bank for carbon storage.
As the climate warms, scientists say, the transformation will be most profound along its southern edge, including the line that cuts across northern Minnesota.
Already, temperatures have warmed enough in the last half century to move the state’s climate north by 70 miles, according to University of Minnesota scientists. At current rates of temperature change, it may migrate another 125 to 250 miles in the next 50 years. Depending on how fast the warming occurs, the southern edge of the boreal forest could move out of Minnesota and much of the United States altogether. Areas like much of the Boundary Waters Canoe Area Wilderness, with shallow soils and bedrock that rises to the surface, won’t be able to support the shallow-rooted conifers that evolved by clinging to cracks and moss.
But this time nature is unlikely to adapt as well as it did when the glaciers retreated 12,000 year ago.
Scientists say temperatures are changing too quickly for many trees, plants and animals to transplant themselves northward. And there are too many obstacles in the way: A century of aggressive agriculture, logging and construction — along with the proliferation of deer and invasive species like earthworms — will alter the landscape as much the climate does.
“We like to think of [adaptation] as being natural,” said Rebecca Bartol, environmental coordinator for the Superior National Forest. “But we have so altered the natural dynamics that to simply walk away now may not get you what you want.”
The birch trees along the North Shore of Lake Superior tell such a story. Once, this stretch was a rich forest of cedar, spruce and white pine. But in the 1800s, like so many of the continent’s forests, it was logged to build the churches, homes and barns of European settlers. In the 1920s, catastrophic fires burned the slash that was left below the ridge that runs along the lakeshore.
What followed was a proliferation of white birch, which is what often grows after a fire or intensive logging. And since then, for many people like Mike Monten, who spent boyhood summers along the lake, the iconic white trunks against blue water created a powerful sense of place — as if they had always been there.
Now the birch are dying, plagued by droughts, insects, diseases and other harbingers of what’s to come. But the seeds of the conifers that should be sprouting below them are gone, taken by the loggers and fires. Instead, in many areas along Hwy. 61, grass and shrubby bush honeysuckle are taking over, squeezing out the few seedlings that might emerge.
“I have this tangible, emotional sense of the change that’s occurred,” said Monten, who owns a second home along Lake Superior near Schroeder, Minn. In the past 15 years, about one-third of the dense stand of birch outside his kitchen window has died. “It’s troubling because I’m not sure what to do. And because I wonder what it will be like in another 13 or 15 years.”
ISLAND IN THE WOODS
On a warm July morning deep in the woods, Dave Chaffin pulls his canoe up the bank of Upper Pauness Lake and surveys the dense wall of green before him. To the untrained eye, this is still the same woods that define “Up North,” a place beloved for the dark-skirted spruce and fir trees that tower almost out of sight. But Chaffin is focused on something else. In all directions, the understory is alight with the emerald green of young maple trees. Just a few decades ago they mostly would have died from the cold; their abundance is a clear sign that an evolution is underway. Rising temperatures, along with winds that carry the helicopter maple seeds from hardwoods in the south and west, are transforming the BWCA. Chaffin, a former advertising executive turned U research assistant, is here to document it.
“This is going to take a while,” he says with a sigh as he steps forward and prepares to count every green-leafed tree in sight.
With field assistant Anna Johnson taking notes, he starts to bushwhack a straight line uphill through dense underbrush.
“Red maple,” he says.
Johnson writes it down.
“Red maple. Red maple. Red oak.”
“Did you get that one?” Johnson asks, pointing her pen at a sprout of green behind a tree.
“Red maple,” Chaffin says.
This was his 61st site, one of 100 that will furnish the data to create a snapshot of the forest in transition. By the end of the summer, Chaffin estimated he had bushwhacked 15 miles through the dense wilderness, paddled dozens of lakes and counted 16,000 young trees.
Later, as his campfire burned high on the brow of a massive rock that overlooked the darkening lake, Chaffin, 37, said he switched directions in life because someday he wanted to look back and see a more meaningful legacy. Protecting the BWCA, where he’s paddled every year since the age of 3, was a risky but compelling choice.
“I rolled the dice and I rolled them pretty big,” he said.
The stakes, he said, are enormous. In its first 50 years the BWCA was protected by the federal Wilderness Act, a law that walled it off from development, pollution and human encroachment. Now a graduate student and research scientist in training, Chaffin plans to arm himself with a new sort of conservation tool, one he says will be most valuable as the climate evolves: scientific knowledge.
Already, he has become an expert on another threat to the BWCA — earthworms — that will compound the threat of rising temperatures.
These invasive creatures, spread mostly by anglers dumping their bait, have taken up residence in about half of the million-acre wilderness, by one estimate. And they are re-engineering the forest floor as they go.
At dusk Chaffin provided a tour of a colony of night crawlers — the most damaging of the worms — residing beneath a massive basswood tree behind his campsite. Each year, the worms can eat a season’s worth of basswood leaves, depriving the forest floor of “duff,’’ the carpetlike layer of decaying matter that is a critical component of northern American forests.
In a healthy forest, the duff keeps tree roots cool, germinates tree seeds and mushrooms, and provides a home for ovenbirds, salamanders and other small creatures. But below this basswood the earth is bare, a circle of hard-packed dirt 30 feet in diameter. Trees that might fare better here as the climate warms — hardwoods such as red maple and basswood — can’t take root in the packed dirt. Instead, the worms create ideal conditions for invasives such as buckthorn and garlic mustard, plants that evolved with them in Europe.
“It’s like a buffet line” for worms, said Chaffin, marveling at their ingenuity. But in the process, he added, they “are fundamentally changing the foundation of the forest.”
U forester Lee Frelich, who has studied their impact on the state’s forests, calls it “global worming,” because they are amplifying the effects of climate change.
So are deer.
Before Europeans arrived, deer were rare in the northeast corner of Minnesota. The dense forest, wolves and deep winter snows kept them out.
But winters are often warmer now, with less snow. There are fewer predators and, thanks to development and logging, more open clearings where deer like to browse. Today, according to some estimates, there are 2.5 to 5 times more deer along the southern edge of boreal forest than there once were.
In large numbers, deer can change the very nature of the landscape by demolishing young seedlings and other green plants. And their food of choice are the very tree species, like maple and white pine, that will fare better in the future.
They can be so destructive to young trees that Frelich describes their impact as “deer savanna-fication.”
The changing climate is bringing other potentially destructive forces to bear on the North Woods as well: bigger forest fires, tree-flattening windstorms, diseases and insects that can take out whole species of trees. Larch beetles, which are now surviving in greater numbers because of earlier springs and milder winters, have decimated about 120,000 acres of tamarack trees in Minnesota, state wildlife officials say.
Altogether, these threats make it particularly difficult for a new forest to rise up below the current one. The hardwood trees, like the maples and red oaks that even now are starting to fill in behind the birch and cold weather conifers, may survive for a while, scientists say. But they face long odds.
A SPECIES REDISCOVERED
There was a time when the state’s foresters were equally pessimistic about the white pine. It once was a dominant tree on 5 million acres of Minnesota forest lands. Then, starting in the 1850s, the timber industry took most of them. Blister rust, a tree-killing fungus brought over in the early 1900s on white pine seedlings from England, decimated them further.
At one point, only 1 percent of the original white pine forest was left in the state.
Now, it’s starting to come back — thanks in part to people like Jack Rajala. A grandson of loggers, he has made it his life’s work to revive the white pine on the timber lands still held by the family business, Rajala Companies.
It’s taken three decades. Rajala lost millions of white pine seedlings to disease, bad siting and hungry deer. Eventually, he figured out how to grow them, including the neat trick of stapling a little piece of white paper at the growing tip of the saplings to deter deer from eating them in the winter.
Today, there are 3 million white pines growing on the 35,000 acres of Rajala forest land. On a walk through one section north of Grand Rapids, he pointed a gnarled finger at the soft green haze of healthy young pine trees — each of them topped with the distinctive white flag.
“The white pine was not a lost cause, not by any means,” he said.
And, it turns out, it is one of the trees that’s ideal for a warmer future.
“We didn’t know 30 years ago that it would be critical to the survival of the northern forests in terms of climate change,” Rajala said. But now, using human ingenuity to restore it in greater numbers is more urgent than ever, he said. “We might not have the luxury of leaving it all to nature,” he said.
The obstacles are formidable, said Dave Zumeta, executive director of the Minnesota Forest Resources Council. About half of the state’s forest lands are in the hands of private owners, who can choose which trees to plant. Blister rust is still a threat. And he’s worried that if demand did take off, there wouldn’t be enough nurseries in the state to supply white pine seedlings.
“But the potential is there,” he said. “We could greatly increase white pine on the landscape if we chose to.”
It is, in fact, becoming a tree of choice. The white pine is a key species in the North Shore Restoration Project, which will rebuild the forest on 39,000 acres of the Superior National Forest above Hwy. 61. The Nature Conservancy will include white pine seedlings in its study of warm-weather species underway near Ely and elsewhere on national forest land. The white pine is also among the trees that the North Shore Forest Collaborative will use to restore a healthy forest ecosystem along Lake Superior from Knife River to the Canadian border.
There, the dying birch trees have inspired a powerful sense of stewardship among landowners who control most of the lakefront, said Bartol, of the Superior National Forest. Like Monten, many of them are already planting white pine and other trees with a different climate in mind.
“There’s some joy in that,” Monten said.
Far to the west, deep in the heart of corn country, stands a towering woods that contradicts all the forces that created the Great Plains in the first place. By some miracle this forest — 400 acres of bur oaks, basswood and three kinds of elm — survived fire, drought, Dutch elm disease and even the plow.
There are no other trees that point the way to the future as clearly as these do, said Frelich. They are a remnant of a fossil forest that seven or eight thousands years ago covered five states — when Minnesota was as warm as Kansas is today. And as warm as northern Minnesota could be in the future.
“You can’t say that about any other forest in Minnesota — that all the trees can withstand the climate of Kansas,” Frelich said, as he stood admiring the twisting limbs that rose hundreds of feet above his head.
Their offspring could provide the priceless genetic stock for northern forests as the climate warms, he said.
There are challenges — scientists must figure out how these trees managed to survive and protect them against the encroachment of development and farming. Most critical, though, is overcoming the human resistance to such an idea, Frelich said. Because for many, that level of meddling is heresy.
“I had someone stand up and say, ‘You think you are God,’ ’’ said Julie Etterson, an assistant professor of biology at the U, who has studied evolution of Midwestern plants through climate change.
Etterson is among the ecologists, foresters and landowners who point out that humans have transformed the landscape throughout history, assuming that, if left alone, the forest would regenerate naturally. But this time, she said, it probably won’t. “I don’t want to see the world become one big weed bed,” Etterson said.
John Almendinger is not so sure about human intervention. A forest ecologist with the Minnesota Department of Natural Resources, he has conducted research on ancient pollen in lake beds showing that jack pine and other northern species survived much warmer conditions in the distant past.
Given a chance to regenerate, he says, these cold weather species may be more resilient than expected. “There is more genetic variation in trees than we think,” Almendinger said.
The Nature Conservancy scientists are quick to point out that they are not planting palm trees in their project to plant warmer temperature trees. At most, they are planting, say, a bur oak seedling from southern Minnesota into the northern edge of its natural range. And they are basing their choices on a sophisticated computer model that predicts tree migration with rising temperatures.
Still, it’s more than a scientific experiment, they say. They want to give a boost to species that might not otherwise have a chance, said Mark White, a forest ecologist with the Nature Conservancy.
“Because the writing is on the wall,” he said.
GARDENING THE WILD
Nowhere is the irony in this debate more profound than in the BWCA.
“We may have to interfere with nature to protect the wilderness,” Frelich said.
This year, for the first time, the U.S. Forest Service took a step toward doing just that. It’s embarking on a plan to carefully apply herbicides to control invasive plants that are popping up inside the BWCA at put-ins, portages and campsites. Such chemical controls are common in other wilderness areas in the west, but it was a difficult choice for the water-rich BWCA, said project director Jack Greenlee.
The problem is still small. The seeds of purple loosestrife, common tansy, St. John’s wort and other plants that hitchhiked in the treads of campers’ shoes and bait containers have now spread to about 14 acres.
But the looming threat of climate change is making the challenge urgent, he said.
“If some of the canopy starts to decline because trees aren’t adapting, then these invasives would be poised to do better,” he said.
Even in the daunting face of a warming world, some advocates say, such human interference is a violation of the very idea of wilderness and the first step toward making the BWCA a garden.
“Do we a want a forest that is pleasing to us humans or do we want the wilderness?” said Kevin Proescholdt, conservation director for Wilderness Watch, a watchdog group for the nation’s 110 million acres of wilderness areas.
He doesn’t want to see invasive plants in the BWCA, he said. But arguments in favor of using herbicides echo the same ones he hears on climate change and wilderness protection everywhere — that allowing nature to call the shots is too dangerous, too unpredictable.
“I would argue that we need to keep wilderness wild, otherwise it loses its core meaning.” he said. “And then there is no reason to have wilderness.”
Outside Cloquet, behind a tall deer fence, a group of scientists have artificially created a window to the future on three dozen tiny plots of land in a massive and aptly named outdoor experiment called B4WARMED.
On each little island strung with wires and temperature gauges, heat lamps and underground cables keep the air and soil several degrees warmer than the ambient temperatures on twin plots nearby. Here, and at an identical site outside Ely, scientists are studying 10 species of trees — plus buckthorn. Half are more southerly trees like oak, red maple and white pine; the others are cold-temperature spruces and paper birch.
Every season, the researchers take thousands of measurements on photosynthesis and growth. They watch what happens season after season to tiny seedlings and larger saplings.
After four years they’ve found what they expected. On the warmed plots, photosynthesis and growth of the cold temperature trees are depressed by about 15 percent, said Peter Reich, a professor of forest ecology at the university and a project leader. The warm temperature trees are 15 percent more robust. And the buckthorn is thriving. Some species have already added a month to their growing season by leafing out early in the spring and dropping leaves later in the fall, said Rebecca Montgomery, a professor of forest ecology and project collaborator.
If funding for the experiment continues, they will be able to predict with exquisite accuracy the temperatures at which bur oak and red oaks will thrive, at what point balsam and jack pine will start to decline, and at what point no forest will grow at all.
Reich said the results will provide critical guidance for the choices foresters will make in the decades ahead. But as long as the world continues to generate greenhouse gases at the current rate, he said, that’s just a holding action. A larger purpose of B4WARMED and its forecasts is to demonstrate that in the long run there is only one way to save the North Woods — one that many are not yet willing to face.
“That we have to fix the problem,” Reich said.
Josephine Marcotty • 612-673-7394