Chemistry of Fire Read online

  When I first came up here in the early nineties, I was taken by the haunting quality of these woods, so different from the ones I’d seen below Superior or even out west. This is the largest boreal forest on the continent, heavy old pine, fir, balsam, spruce, maple, birch, cedar, and aspen, hung with ancient streamers of silver moss, towering out of a maddening understory of deadfall, brush, and vines. Wild rose, leatherleaf, and thorn apple grow in crazy tangles amid thistle and lady’s slipper. Fungal villages populate the woody rot as fallen trees are sucked back into the earth like cotton candy going into a child’s mouth. Hiking in from the trailhead, we lost sight of the road after ten or fifteen steps in a wall of willow as high as our heads. Then we were in the eternal twilight of this mythic world, the blackness almost luminous at times.

  The forest is actually a northern jungle. Its darkness steals the sky and leaves you in a chaotic bushland churning with life and destruction. Where any light comes, it comes in great pillars and slim shafts, illuminating a mist that looks and smells like decay mixed with the incense of a cathedral. The scent of clove and myrrh mixes with the aroma of dying leaves. Sometimes, too, that radiant dark escapes the forest and overspreads the open land, and only when the wind comes to ripple the water and set the aspens dancing at its edge do you recognize that you’re seeing a deep black lake alive with fish. The lakes here go on endlessly, from the east to the west where the glaciers went. They are pressed so close together that you can paddle and portage from Thunder Bay to the Little Fork River and Muskeg Bay. In the 1700s, voyageurs crossed them on their way from Montreal to the Pacific, covering some three thousand miles.

  If you come from the city, one of the glories of this place is the quiet. At the edge of a lake, I heard the pebbles rattle as even the smallest waves withdrew. When a breeze came up, the aspen leaves clattered like coins. I heard a bear sneeze in the forest. And one day as I sat in a canoe trying for a walleye, a moose crashed out of the forest trailed by her calf and swam across the lake not fifty feet in front of me. They climbed the far bank and melted into the darkness. Then it was silent. So silent that when a crow flew overhead, his wings cut the air with a sound like someone ripping long bolts of silk. Fire is the enemy of this quiet, this cool darkness, and one day it will bring the noise and sunlight down to the forest floor for the first time in centuries.

  On July 4, 1999, the temperature here hovered around a hundred degrees, as it had for days. A cold front had descended into southern Canada from over the arctic pack ice. When that cold, fast-moving air met the steamy hot air north of Lake Superior, it was like throwing water into hot grease: it exploded into the stratosphere, creating what meteorologists call a “mesoscale convective complex.” Far larger than a thunderstorm, more powerful than a supercell, it pulled winds down from twenty thousand feet or more and began working its way from South Dakota to the northeast, knocking down power lines, felling trees, sucking up thirteen hundred acres of the Chippewa National Forest, and expelling inundating rains that damaged nine thousand acres of lakeshore as it moved across Minnesota.

  As the heat from the land fed the storm complex, it built in intensity, and by the time it reached the Boundary Waters, it was putting out sustained, straight-line winds estimated as high as a hundred miles an hour. For twenty minutes the storm locked on to the land here and flattened an area of nearly half a million acres. Then it was gone to the east, and the quiet descended once again. Almost immediately, the locals began referring to this event as the Blowdown.

  The wildland firefighters who protect the Boundary Waters had long referred to the area as the “asbestos forest,” because it was resistant to large fires. The reason it wouldn’t burn explosively was its lack of tinder or what they call one-hour fuels, as well as the absence of people to set fires. One-hour fuels dry out quickly. One hour after the end of any rainfall, they are dry enough to burn. Suddenly, in little more than a quarter of an hour, the forest had been transformed. Pine needles and small branches, dead and drying, littered the forest floor, and the so-called “fuel load”—the amount of fuel available to burn—went from between five and twenty tons per acre to between fifty and one hundred tons per acre. A forest that was unlikely to burn became a forest with the highest fuel load in North America and a probability of burning—perhaps catastrophically—that was put at nearly 100 percent. The fuel load was so high, the risk of uncontrollable fire in extremely harsh and remote terrain so great, that there were no computer models capable of testing what might happen.

  The closest historical model was 128 years old from the area that encloses the Green Bay in Wisconsin. Logging, railroad building, and generally careless use of the land had left not only a huge fuel load on the forest floor but also numerous small fires burning unattended in the summer of 1871. Loggers burned slash, railroad crews cleared land for the Chicago and Northwestern line with fire and ax, and travelers routinely walked away from their fires without bothering to put them out. Everyone assumed that the rains would come, as they always had. That summer and fall they didn’t.

  It was dry and hot, and small fires scuttled along beneath the forest canopy like strange creatures on the ocean floor, consuming whatever was readily combustible. When any wind came up, they burst up into the tree limbs, and in September a crown fire exploded, setting loose thousands of birds across the town of Peshtigo near the Michigan line. A crown fire burns hot and travels rapidly through the tops of the trees. Ahead of it, whole trees, superheated by the flame front, exploded. But people were used to fire and smoke in the fall, and they stayed and stayed, waiting for rain.

  Catastrophes are built out of the small pieces of our lives that we leave lying around unnoticed. The clouds came in, and it looked like rain, but all they got was wind. The front and the rain it carried were still in the Dakotas. For several days the wind blew and blew, but no rain came. The small fires began to consolidate.

  Fire and weather are wicked sisters, born of the same blood: heat and air. They always travel together, aiding each other, bringing gifts and making mischief. Weather brings rain and makes the forest grow. When it grows too much, fire clears it, and then the rain makes it grow again. And sometimes, when a cold front approaches a big dry forest with a source of ignition inside of it, the world explodes, and the forest simply ceases to exist. If the fire is hot enough to burn through the root system, the forest never grows back.

  Weather makes fire and fire makes weather, and the winds created by the Peshtigo fire ripped full-grown maple trees out of the ground by the roots and sent them aloft as firebrands, torching more forest up to three miles away. Papers from the town were found as far away as Canada and Michigan.

  There is no clear line between conflagration and deflagration, between fire and explosion. The difference is the speed with which the flame front progresses. Stephen J. Pyne, author of Fire in America, writes, “In heavy fuels and under favorable conditions, the coalescence, which begins with the upper convective columns, occurs rapidly. The resulting holocaust is a synergistic phenomenon of extreme burning known as mass fire.” Peter M. Leschak, author of Ghosts of the Fireground, refers to the fire at Peshtigo as “a kind of rolling explosion.” And since it consumed 1,280,000 acres of forest in about four hours, that would appear to be accurate. (Across the lake in Michigan, fire consumed 2.5 million more acres the same day, October 8, 1871. The Chicago Fire, which happened to begin on the same day, got all the headlines.)

  Only after the Peshtigo fire had done its damage—whole towns burned to ashes and up to twenty-five hundred people killed—did the rains come at last. If conditions were the same in the blowdown today, this Minnesota forest could burn from Lake Superior to well across the Canadian line in the time it took those rains to arrive. In the firefighter’s art, the term “conflagration” is used to refer to a mass fire that is on the move. (A firestorm is stationary.) A conflagration produces its own wind in what some firefighters call a “fire tornado.” It is a ballet of energy between sky and forest and can push
hot columns of gas to fifty thousand feet. When they cool, the down-rushing tornadic winds explode outward in every direction in an expanding dome of fire. As the fire uses up all the available oxygen, the superheated fuels send great amoebic masses of unburned gas aloft, where they explode as soon as they reach fresh air. Horizontal vortices develop from those gases and reach out to torch trees and cause preheated structures to burst instantly into flame. During the Peshtigo fire, wagons in open fields caught fire far from any source of ignition. A mother was seen running down the street, her hair streaming back, skirts flying, clutching her baby. She burst into flames as she made for the safety of the river, which flowed through the center of town.

  Fires of such intensity are not unknown in this region. The Little Sioux fire in the Boundary Waters Canoe Area Wilderness—the asbestos forest—burned nine thousand acres in six hours in 1971 without the unusual fuel load. Making matters worse is the fact that there is only one escape road in the most densely populated area, the Gunflint Trail, and it’s a cul-de-sac at its northern end, which is surrounded by the very forest that people would be trying to escape. The only way out is south, through nearly sixty miles of forest to the town of Grand Marais on Lake Superior. It brings to mind the fire at Paradise, California, which killed at least forty-two people who simply could not get out.

  Ellen Bogardus-Szymaniak, who is the fire behavior expert with the Superior National Forest, said, “The potential for large, explosive fires has not diminished. But what we’ve done is made it so we can slow the fire from exiting the wilderness. And that’s all we’ve ever wanted to do anyway.” Although it’s been a wet year in Minnesota, she said, “We still have very high intensities, and the blowdown will ignite even in very, very damp, wet conditions. It’s like a big woodpile.”

  After the Blowdown, the fire district at Grand Marais, on the southern edge of the forest, was reinforced with more people and equipment as summer turned to fall, both prime seasons for wildland fires. The Minnesota Interagency Fire Center in Grand Rapids staged chainsaws, protective clothing, radios, tools, and other firefighting equipment in caches from Ely east to the Gunflint Trail. Various agencies contributed to leasing a helicopter, which carried a two-thousand-gallon water bucket, and air tankers that could scoop fourteen hundred gallons from the surface of a lake in one eight-second pass. They hacked helipads out of the forest and acquired four new fire engines.

  They understood that if conditions were right, if a so-called “plume-dominated” fire similar to the Peshtigo fire were to begin, there would not be enough equipment or enough manpower. Once it happened—if it happened—the only strategy would be to try to move the people, who occupy about six hundred cabins, resorts, and homes in the area, down the Gunflint Trail before the fire overran it and cut them off. If the fire were to burn south to Lake Superior, even that might not work.

  My wife Debbie and I stayed on the edge of the blowdown in a cabin that had been built by hand on Flour Lake. The lake was enclosed on all sides by the wilderness. Our first night, we sat by the water and watched Mars tow the full moon in an arc above the palisades. A front came in, and clouds hurried high to the northeast, cold and gray and tumbling, illuminated from below by the low-angled light of the rising moon. A loon cried all night long.

  In the early morning, a black beaver with a white nose came to sit as still as a statue on a stump outside our window. A quarter mile across the lake a great, dark humpbacked hill rose from the silver water with a green that made me think of the dinosaurs that would have lived here before the glaciers cut these lakes out of Precambrian bedrock. Farther east, beyond the rising palisades that cleaved clean to the bottom of the lake, was the paler green of the sunlit forest. I could see three miles down the lake to where the misty rampart of the wilderness stood against the white sky. The day grew windy and white, so white that where water met sky, there was no line to show which was which.

  After hiking and paddling in the undamaged forest farther south, we went to see the worst of the blowdown on a day when the sign at Station Number One of the Gunflint Trail Volunteer Fire Department read: “Fire Danger—EXTREME.” As we headed up a small dirt road, a healthy-looking gray timber wolf trotted ahead of the car for a hundred yards and then loped off into the trees. Farther on, we stopped for a bald eagle, which appeared to be sharing some roadkill with a conspiracy of ravens. (The raven, largest songbird in North America and as smart as a dog, was also made nearly extinct by logging.)

  We went in at the Kekekabic Trailhead. The trail ran up a steep, rocky slope to a ridgeline heading straight west along a gully. Half a mile in, we began to see the scope of the destruction. Thick evergreens had been snapped in half lengthwise and lay on their sides. Some trees had been torqued so rapidly and with such force that they had simply exploded into a messy kindling shrapnel. Stands of young aspens pointed the way the storm had gone. Their fibers had been permanently stretched by the wind so that they stood bent in the shape of Cs, some all the way to the ground. We passed whole areas where the trees had been blown in half, their crowns and upper stories gone. They stood in odd, jagged ranks, as if a cathedral had had its roof blown off and lay open to the sky. Everywhere were great piles of mature trees and even old-growth cedar and pine, turned into jackstraws and stacked in towering heaps, some of them spring-loaded like drawn bows. A two-foot-thick tree trunk stores a tremendous amount of energy when it’s spring-loaded, and if it is cut or breaks, it rebounds with the force of a bomb going off. Not easy or safe for crews to clear.

  Aside from the trail on which we hiked and a few others like it, the forest ran uninterrupted for hundreds of miles, and the shattered trees made the land impassable. Some trees had been uprooted, leaving root balls ten or more feet across erupted out of the earth, their fingers clutching huge rocks in a final spasm. Walking through there may have been hazardous, but I couldn’t imagine what it had been like for the crews who’d had to clear this yard-wide trail. Leschak was on one of those crews. He found a note stuck to a twelve-foot-wide cedar root wad. It read, “Welcome to Hell” and was signed, “Voyageurs Nat. Park Crew.” He’d come from two hundred miles away.

  We followed the trail through perhaps another mile of destruction. On the north side, the land angled sharply upward, iron red and black and rocky, piled high with blown down trees too dense to scramble through without a power saw. To the south, the terrain dropped away to rise again in cliffs, and down there we saw more of the same—great middens of burst and fractured trees. Some people think it’s ugly, a sad thing that needs cleaning up. I think it’s beautiful, a great wonder where nature leaves her signature. We’re not used to seeing such clear evidence of her power. A Niagara of wind came through here, hard as water, and tore a hole in this forest measuring half a million acres.

  An hour and a half in, the gulch below became swampy as the trail turned downhill. The cliffs to the south dropped away, and we descended a natural staircase of great boulders. A creek, crackling like fire, drained into a field of tall yellow-green grass with oxbow waterways gleaming through it. Swaying in the wind, the grass formed French curves and arches. In the waterways, lily pads rode the wind-freaked surfaces in pale purple and silver-green formations. The few scattered cattails appeared so intensely green and brown against those pastels that they looked as if they’d been painted there.

  We found a flat, mossy rock and sat and ate sandwiches. We could hear the wind long before it reached us. There was no other noise. For perhaps a full minute, we heard it coming, deciding to come, preparing to come. It began as a far-off, rushing whisper and grew steadily until the trees three hundred yards away began to rustle and sway. At last we saw it descend from the crowns to bend the grass in long, undulating waves, changing all the colors from yellow to green to silver and brown and back again. And then it was gone. But one day it hadn’t gone. It had just kept on building, and nature had had a game of pickup sticks with this forest. Soon trees had been exploding, flying through the air, pitchpoling through t
he forest, tearing one another apart. The cannonade of sound lasted twenty minutes, and twenty-five million trees went down.

  On a day like this the fire will come. The report called Fuels Risk Assessment from fall 1999 says it will come. So does the six-pound volume entitled Final Environmental Impact Statement: Boundary Waters Canoe Area Wilderness Fuel Treatment from 2001. On a day like this, then, when the wind is ten to twenty knots, with gusts to thirty from the southwest, it will come. Then the cold front will arrive, the wind will switch directions ninety degrees, and the fire will appear as a gleaming wall, roaring and towering 150 feet above the tops of these trees, and it will sweep across this bog in seconds and take the grass and water with it.

  Fire is good for forests. But catastrophic mass fires can burn down through root systems to bedrock and change an entire ecosystem. The Peshtigo fire destroyed not only an old-growth forest but also the ecosystem of microorganisms beneath it in the soil. That fire ensured that the forest would not grow back. The land was cleared completely. Grasses grew. Immigrants from Europe moved in to start dairy farms on the newly arable land.

  Here is why this forest still stands: In 1924, Ernest Oberholtzer, a prodigious explorer who lived here, learned that the local paper-mill baron, Edward Backus, was planning to build seven hydroelectric dams that would destroy a large area, including what we now know as the Superior National Forest, Voyageurs National Park, Quetico Provincial Park, and the Boundary Waters Canoe Area Wilderness. It was the legacy of the beaver: people were coming to cut down this forest to make paper.

  Oberholtzer fought Backus all the way to the White House over the next few years. The concept of lands that couldn’t be used for anything was an alien notion at the time. Oberholtzer’s victory in Congress in 1930 marked the first time legislators had voted to preserve any federal land as completely wild. It is because of Oberholtzer that these woods retain their strange and mystical character. “Holtzer” means “timber man.”