As published by Take Part.

LAC LA BICHE, Alberta—“This was a monster,” says Joe Gauthier. “I’ve had big fires, but this was a monster.” Clad in the baseball cap and shirt he was able to grab when he evacuated his home in Fort McMurray on May 1, he sits in a fast-food restaurant in Lac La Biche, a small community southeast of the city struck by Canada’s third-largest environmental disaster on record. Hired in 1974 as the first firefighter in what was then a fledgling community, Gauthier rose to the rank of captain in the Fort McMurray Fire Department, which he served for 31 years. He saw the city grow into a boomtown over the past decade as oil companies set their sights on Alberta’s tar sands. As the raging fire overtook the city, he was forced to leave. “If it weren’t for these new knees,” says Gauthier, pointing down at the products of his recent surgery, “I’d have been out there fighting it myself.”

As is true south of the border, Canada’s wildfires are getting bigger, and the annual wildfire season is growing longer. In the past week, the blaze firefighters have nicknamed “the beast” has displaced more than 88,000, hit the country’s oil production, and grown steadily in size. Ignited by an unknown cause nine miles west of Fort McMurray, within a week it morphed into a 565,000-acre leviathan—20 percent larger than the city of Los Angeles—jumping highways and four rivers in the process and triggering a mandatory mass evacuation as crews met the flames in a series of pitched battles. The urban skirmishes couldn’t prevent the loss of more than 2,400 structures. The damage was a shock in an era of modern detection and suppression techniques. It approached the oil sands production areas, at one point reaching within 20 miles of a bitumen processing facility’s highly combustible chemicals. Estimates of the damage are higher than 9 billion Canadian dollars, on pace to be the costliest natural disaster in the country’s history. Though 90 percent of Fort McMurray was saved, its 61,000 residents are blanketed with uncertainty as officials block their return until the city is deemed safe.

A cocktail of heavy winds and dry weather pushed the blaze into residential areas, where at least some homes featured easily ignited wood-shingle roofs. Fire management policies and techniques—and luck—are also determinants of how big a fire becomes. And crucial parts of the forest are getting drier as temperatures are getting warmer. Mike Waddington, ecohydrology professor in the School of Geography and Earth Sciences at McMaster University in Hamilton, Ontario, likens the role of climate change in the beast’s size and speed to a baseball player who uses steroids: “On a particular home run, you couldn't say he hit that home run because of steroids. But he created the conditions that allowed him to hit more home runs.” Still, it may turn out that the most significant way climate and the beast were related was the opposite of what most people think: Climate change didn’t so much drive the fire as the fire (and future ones in the region) could drive climate change.

Forests are designed to burn. It takes the heat of a fire to burst the dense, resin-covered, closed cones of jack and lodgepole pines, spreading seeds for new growth. Much of the province’s boreal forest serves as late spring and early summer kindling. Charred trunks and hungry flames are inextricably tied to forest health; a blaze works as a clearing mechanism for accumulated organic debris. As Alberta maintained a policy of total suppression of wildfires for decades, fuel built up, so that when fire did return—and every forest will eventually burn—it was hotter and bigger than it would have been had nature been allowed to take its course over the years. An especially intense igniter is the black spruce tree that thrives in Alberta. The highly combustible tree is a scourge to fire crews because if ignited, it can spray embers more than a mile. “For a while, black spruce was public enemy number one,” says Waddington.

The Fort McMurray fire, like the devastating 2011 Slave Lake fire in Alberta, differs from blazes common in the province as recently as the turn of the century. A warm, dry winter and spring left little snow in the area, depriving the forest of moisture. Hot, windy weather dried out the trees and grasses of Alberta’s picturesque heartlands. Then, the weather formed what Gauthier calls the “crossover to perfection” when relative humidity, temperature, and air pressure all hit 30: 30 percent humidity, 30 degrees Celsius, 30 pounds of barometric pressure. In Fort McMurray, the magic numbers aligned on May 3 and 4. Within days, the fire became so large and intense that it created its own weather system, forming pyrocumulonimbus clouds, or clouds with lightning strikes, which set off additional fires.

Peat is an important carbon sink in the boreal forest, holding thousands of years' worth of accumulated carbon. Drier weather—consistent with climate change models—makes the peat more susceptible to burning and releasing greenhouse gas. (Photo: Leyland Cecco)

In wildfire fighting, fire crews rely on natural and human-made barriers—rivers, highways, lakes, mountain ridges—to help temper an errant fire. Peat, or muskeg, a swampy ground cover, helps slow the spread of a blaze, starving it of fuel. In the northern sections of Alberta where the fire raged, the forests are pockmarked with bogs rife with organic matter—stored carbon. “Sixty percent of the boreal in the region is covered by peat,” says Waddington. Sphagnum, a natural fire retardant, grows plentifully in these bogs—with the right levels of moisture. But dry weather turned peat from a fire barrier to a global-warming catalyst.

Peat fires are messy fires. They burn significantly longer, are harder to extinguish, and release significantly higher amounts of carbon dioxide and methane into the atmosphere. These greenhouse gases contribute to the climate conditions that ripened Alberta’s boreal forest for the beast, creating a positive feedback loop. The fires also burn deep. After a wildfire tore through Slave Lake, displacing the town’s 7,000 residents and destroying 374 structures, Waddington’s research team discovered the fire reached depths of five feet. When peat makes contact with a fire, it combusts at a temperature lower than flame but still smolders. Because the peat is porous, oxygen fuels the flame and carries it beneath the surface, where it becomes elusive. These deeper burns mean more legacy carbon accumulated over centuries is instantly released. Only a few days after the Fort McMurray fire started, crews suspected it had burrowed underground while it surged forward; ground cover with little moisture provided an easy entry point for the flames. Traveling undetected for miles and immune to the changing seasons above it, the flame reemerges far from the original fire. This becomes a threat: Fire crews digging perimeter lines have been caught by a flare-up from underground.

“It can take weeks to months, and certainly potentially over winter, for those smoldering fires to go out,” says Waddington.

In 1997, underground peat fires in Indonesia spewed tons of carbon dioxide and methane into the atmosphere, by some estimates making up nearly half of all global carbon emissions for the year. In 2010, massive fires spread throughout Russia’s peat, contributing to the deaths of 56,000 from poor air quality. Last year’s peat fires in Indonesia were the worst on record, torching an area the size of Massachusetts. Canadians need not worry about fires reaching these extremities: Both Russia and Indonesia drain their peat reserves to make room for agriculture, a practice that significantly increases the risk of long burns at the cost, in Indonesia especially, of extensive damage to wildlife habitat. Still, Canada has 30 times as much peat as Indonesia has; more than 680,000 square miles mix with the boreal topography.

Experts fear things will only get worse. Two of Canada’s costliest fires, both in Alberta, have occurred over the last five years. Research by Uldis Silins, professor of forest hydrology at the University of Alberta in Edmonton, shows that over the past five decades, as suppression policy reigned, the total area burned in Alberta decreased. But when he and his colleagues looked at the sizes of the largest fires, they found that the past 15 years saw increasingly large blazes. “As burning conditions change, under extreme fire weather conditions, that’s when we go beyond our capability to suppress them,” he says.

Sometimes it takes a destructive fire to change policy. Before the Slave Lake fire, Maria Sharpe’s job didn’t exist. As wildfire management specialist at the Lac La Biche Fire Centre, a division of the provincial government, Sharpe develops preventive fire strategy. Her district and Fort McMurray are the only two in the province to have developed wildfire management plans; while Lac La Biche has executed its plan, Fort McMurray’s was still in the works when the beast hit.

With careful planning, forestry experts have ways to mitigate the power of megafires. Deliberate burning of forest, called a prescribed burn, and allowing natural fires to burn under close supervision are strategies that make sense from an ecological perspective. “Large tracts of mature forest just aren’t natural,” says Sharpe.

But they can be a tough sell to the public. After 400 families in Los Alamos, New Mexico, lost their homes when a prescribed fire burned out of control in 2000, the public’s tolerance for the forest management strategy sank. Residents of a California town almost turned violent when officials told them that a naturally occurring fire threatening their homes had not been put out right away, so it could clean up accumulated fuels. And burned tracts accenting untouched forest lack the aesthetic appeal many want when they think of forests. Experts worry that if changes don’t come quickly enough, Canada will see more fires like Fort McMurray’s.

While cooler temperatures and softer wind has slowed the fire’s progress this week, it will likely take months for it to go out. “At this point, only weather can kill it,” says Gauthier. The plan for the fire crews now is to guide it, using a nuanced mix of science and intuition, away from homes and other structures.

More than a week after the fire forced Gauthier’s evacuation, the peat continues to frustrate support crews. As the northern sun begins to set over a road 18 miles south of Fort McMurray at around 9:30 p.m. on May 11, acrid smoke drifts gently off the burned peat and hangs heavily in the air. Bulldozers are effective at turning over the peat to extinguish it, but the work is slowed by uprooted trunks, called jackpots by fire crews, littering the ground.

A crew from Fort McMurray relies on a repurposed HydroSeeder to spray down the smoldering peat. With each blast of water, fires pop up somewhere else in Whac-a-Mole fashion. The crew is tired of traversing the section of highway since early morning, and there is little to show for the day’s work.