We will continue with our IPCC series next week; in the meantime, here is a follow-up to our series on climate change and extinction.
Early October, and half-frozen snow sugars the dark green firs and sifts down through the upturned wooden fingers of dead and dying birches in Franconia Notch, in the White Mountains of New Hampshire. The snow we expected; the dead birches were a surprise and a warning.
Early October is foliage season in the White Mountains, and my husband and I had joined my friend, Tom Wessels on the unofficial field trip he leads through blazing trees and unpredictable weather every autumn. Tom is a science writer and ecology professor, and he is the source of every statement of fact in this article, unless otherwise specified. I am no longer officially his student, and most of the grad students on the trip were strangers to me, but I do not pass up an invitation to walk in the woods with an expert.
Franconia Notch is the most dramatic of the three passes that cut through the famously rugged White Mountains. It is a narrow, foreboding glacial U. While the Whites are not tall as mountains go, they rise dramatically out of fairly low country and the turbulent storms that converge at their peaks make these mountains dangerous. Tree line here is only about 4500 feet, so a reasonable day hike can take in three different major ecological communities, one layered upon another, moving up the mountainside. We planned to tour all three, to start in hardwood forest and move through the spruce and fir-dominated subalpine layer and visit the exposed alpine tundra on the ridge top. From the trailhead in the Notch, we could see Cannon Mountain and Franconia Ridge sweep up above us into the clouds, almost parabolic in their steepness. The air, as we stepped out of our cars, was startlingly cold in comparison to the mild weather we’d left back home. There was no rain yet, but the day felt wet.
Tom had chosen a route that would take us up to Franconia Ridge, across three named peaks, and back down in a loop back to our cars. He had hiked the same trails before and was familiar with the route, but had not been this way in a few years. Though the trip was not associated with any particular class, part of the point of the hike was that Tom would take the opportunity to teach. His interest and his expertise lie in “reading” the landscape for its history. An oddly shaped tree or a shift in forest composition from one area to the next is a clue to what happened here decades, or sometimes even centuries, before. For those who can read the signs, events can cast a long shadow, shaping the growth and character of a place for generations. So as we hiked, every rest break became an opportunity for Tom to describe what was growing there and how the soil, topography, climate, and history of the place could all be seen in the identity of the forest at that spot.
One of the areas we walked through was the paper birch band. Paper birch, or white birch, is that pretty plant with the white, peeling bark. There are other birches that look vaguely similar, but paper birch is the most iconic and is famous as the source of birch bark canoes. It is a far northern plant, mostly native to Canada, and its small, light seeds allow it to colonize bare ground quickly. Around the turn of the last century the Whites Mountains were heavily logged for red spruce, another species adapted for cold, harsh weather. In Franconia Notch and several other places, paper birch moved in where the spruce had been removed, producing a distinct band at 2,500 to 3000 feet, the cheerful-looking shadow of clear cuts a hundred years old. So our trail took us through the birch band—and we found the birches were dying.
The birch band is temporary, as ecological time goes, since they belong to an early phase of forest development and paper birches are not long-lived trees, but these birches had not died of old age. They had not died alone, either. White birches are dying in many places across New England, pushed by a combination of factors including climate change.
Paper birch is a cold-weather species, capable of growing farther north than any other hardwood. It can cope with temperatures that would kill almost anything else, but it cannot withstand the rapid freeze-thaw cycles common in milder winters. The species is also struggling with a pair of relatively new diseases introduced several decades ago. Under the combined stresses of new diseases and a new climate, paper birch is already dying out of areas where the soil is not to its liking. The wood rots quickly, but the iconic bark is rot-resistant, and a New England nature lover can now easily find forests littered with broken trucks and hollow tubes of ghostly white bark. Some birch groves are hanging on, and of course trees farther north in Canada are still doing well, but the species could easily be the first tree the United States loses to climate change.
This bears repeating; anyone reading these words could well live to see the paper birches of New England become a memory.
This is not the first time we have lost a tree. The generation that logged the red spruces of Franconia Notch also watched the sweep of the chestnut blight. The American chestnut had been one of the largest and most common trees in eastern North America. In the South there were places where every other tree was a chestnut. The wood was strong, beautiful, and rot-resistant. The nuts were abundant and delicious to both human and beast. The blight, accidentally introduced from Asia, killed almost of these trees within a human generation. A few individuals survive, and a blight-resistant variety is being bred, but an experience of the forest that was utterly normal just decades ago is now completely lost. My generation will not live to know what a whole forest of chestnuts in bloom smells like.
The chestnut blight had nothing to do with climate change, but it does presage the same kind of loss that climate change could now be causing. Paper birch does not have the economic importance that the American chestnut did and its value as wildlife food is considered only moderate, but it is one of America’s most widely recognizable trees. Even people who know nothing else about trees can often recognize paper birch. In the movie “White Christmas,” paper birch and the similar-looking grey birch are used as visual cues of New England, even though the set does not otherwise look much like Vermont. This tree is part of the identity of one of the most beloved regions in the country and it is part of American’s cultural inheritance. And in another generation Americans will have to go to Canada to see it.
Tom knew all this when we hiked up to Franconia Ridge that day. He had been explaining it to students, including me, for years. But he had not known the birches in Franconia Notch were dying, specifically; last time he had hiked this route, they had appeared healthy. Now the canopy was open, broken, and bare. Almost all the birches were dead. They had gone from apparently healthy to dead in less than seven years. Our resident expert stood, turning in place, staring nearly slack-jawed at the rotting white trunks missing limbs and hanging at graceless angles, leaning on each other, bare to the grey sky.
Perhaps most hikers would not have noticed the difference. Most people, moving by, puffing with the effort and looking at their shoes, probably notice a few dead trees and think little of it. Maybe they chalk the damage up to an ice storm or confuse the dead birch band with a fir wave (a natural phenomenon that only affects firs), if they notice it at all. But to those who pay attention to trees and are familiar with this particular landscape, the damage glares like a neon sign. And it is moving astonishingly fast.
We continued hiking; summiting the peaks and circling back around, exhausted and finally snowed upon, but in good spirits, for the most part. It was a good hike. But from up near tree line in the stunted forests of dark firs and alpine shrubs we could look out upon the fins and coves of the mountains, rumpled like a giant blanket and partially obscured by blowing half-frozen snow, and we could see a line along the mountain sides where the autumn canopy below us was interrupted. Bare, white trunks, broken, marched their way in a distinct band as far as we could see. The sign of history, the paper birch band, standing ghostly now, ourselves witness to another turn in the story of the forest and a bauble of our children’s inheritance being stolen.