A longer growing season is not good for this tree, Frelich explained, because it goes hand-in-hand with warmer soil temperatures. And paper birches, which range from here to Alaska, can’t tolerate warm soil.
That’s why paper birches are among the species that Frelich says will migrate from the Boundary Waters entirely if, as the UN’s Intergovernmental Panel on Climate Change predicts, average global temps rise another 2 to 11.5°F by 2100. Other trees in Frelich’s climate-change dead pool include balsam fir, black spruce, white spruce, jack pine, and red pine. That’s nearly every species for miles around. Take those trees away, and this forest is rendered unrecognizable as North Woods.
“If the trend continues, Boundary Waters is going to lose the boreal forest as we know it,” Frelich said as he poked around the campsite. “I don’t see any way around it.”
After a dinner of campfire-grilled steaks (packed frozen and thawed on our first day’s journey), I proposed a sunset hike. Behind our campsite in one of Frelich’s research plots, we walked past a waist-high grove of birch saplings regenerating after a prescribed burn in 2002. Those saplings, Frelich said, have the best chance of adapting to a warmer 21st century. That’s because most boreal trees release seeds every time the forest burns, and the seeds that succeed become new trees that are genetically coded to cope with the climate they’re born into.
Climbing up a ridge, I scrambled across pink granite boulders unearthed by a fire that burned away the soil. At the top, I hopped from boulder to boulder above the tiny birches. The setting sun painted distant granite outcroppings a radiant rouge. My eyes told me I was somewhere out West, maybe Utah’s redrock country. Then a moose sauntered out of a black spruce bog in a draw that had escaped the flames, and my mind snapped back to Minnesota. She climbed the ridge, glanced back, dipping her bulbous brown nose to give her eyes an unimpeded view, then disappeared down the other side.
I took a closer look at the ground. Vigorous, nascent blueberry bushes, a few ankle-high spruces, and several jack pine seedlings were poking up: boreal forest reborn, at least for now.
MORNING BROKE ON DAY TWO with a calm that had us scrambling into the canoe to take advantage of the flat water. We paddled to another research plot a bit farther down Three Mile Island–a grove of ancient, if stunted, northern white cedars.
The canoe nudged ashore near trees that Frelich dated at 550 years old. Their granddaddy–a cedar estimated at 1,000 years old, quite possibly Minnesota’s oldest tree–stood a few feet inland. Only about 25 feet tall, its bark was a weathered and gray, with a hole in the trunk that reminded me of the agonized face in Edvard Munch’s Scream.
This plot is important for Frelich’s research. These cedar trees could be the future of the Boundary Waters, because they are one of the area’s few native trees that could prosper in a warmer climate. All across northern Minnesota, however, white-tailed deer keep white cedars from branching out across the landscape in a classic climate-change domino effect: Milder winters allow more deer to survive and propagate in spring. The deer (whose population is at an all-time high) need to eat, so they munch the cedar saplings. And the cedars take a big hit. Now deer are encroaching on the BWCAW, where 150 years ago they were rare and caribou (now gone) were common.
Soon we were off to another plot on nearby Eagle’s Nest Island, which was scorched last year when the Cavity Lake fire burned more than 30,000 acres of forest. The standing dead trees sport black, bubbled bark the texture of burnt wheat toast. Poking around, Frelich found new life. He pointed to fresh shoots of liverwort, a plant with bright green sprigs that belie its pallid-sounding name. But his explanation of their role in a resurgent post-fire forest is suddenly interrupted. Three planes roar low overhead, our first indication that there is a problem very close by.