Firefighters started to realize the uniquely destructive nature of the Fort McMurray wildfire when they saw aspen poplar trees instantaneously and loudly explode into fire.
As veterans of Alberta’s wildfire wars will tell you, the aspen does not readily burn, not with its green leaves and thick twigs. But in the hottest of fires, gases are released in the combustion process so it’s possible for a tree to heat up, ignite and catch fire all at once, as if it had exploded.
“The last time we’ve seen anything like this was the Chisholm fire, which is the most intense fire that we have recorded in the fire record, not just for Alberta, but for Canada and for the world,” says University of Alberta wildfire specialist Mike Flannigan.
The 2001 wildfire that went through the central Alberta hamlet of Chisholm burned at 233,000 kilowatts per metre, Flannigan says. At the 2011 Slave Lake fire, the heat was 33,000 kilowatts per metre. For context, if a fire is burning at 10,000 kilowatts per metre, it’s generally deemed that aircraft water bombing is less — or no longer — effective.
The Beast is what regional fire chief Darby Allen calls the Fort McMurray fire, and it might well be that the Fort McMurray fire is burning as hot as Chisholm, an issue that Flannigan and his team will soon investigate. The two fires already share one other indicator of unprecedented intensity, with both fires producing pyro cumulonimbus clouds, thunder and lightning storms generated by the fire’s smoke column.
“The general consensus is we’re seeing more area burnt, more extreme fire weather and more large fires overall across the boreal forest,” says University of Alberta instructor Jen Beverly, an expert in wildfires.
The Alberta government is struggling with this trend.
Four times in the past two decades, always in response to ever worsening wildfires, the government has brought together groups of experts to report on how to deal with these most catastrophic of fires. Four times there has been no end of recommendations — and many of them have been acted upon. Yet the fires keep getting more destructive.
In 2001, the Chisholm fire destroyed 10 homes. In 2011, the Slave Lake fire destroyed more than 500 structures. So far, the 2016 Fort McMurray fire has destroyed more than 1,600.
So where do we go from here?
Wildfires aren’t abnormal, but are a normal part of the life, death and regeneration of the boreal forest. As Canada’s national wildfire plan from 2006 puts it: “Although often portrayed as a menace to society, wildland fire is, in fact, a natural process that is essential to maintaining the health, productivity, and diversity of most of Canada’s forest ecosystems.”
Canada has 402 million hectares of forest and woodlands (one hectare is about the size of a football field). On average about 2.5 million hectares burn in wildfires each year. But Canada has had three bad fire years in a row, with four million hectares burned in the summers of 2013, 2014 and 2o15.
Across Canada, fire control units have got highly efficient at putting out most wildfires. In Alberta, a network of 126 lookout towers quickly spot fires near human settlements so that water bombers, helicopters and ground crews can move in. That rapid response sees about 95 per cent of fires put out one day after they’ve been spotted.
But some fires escape control.
Forest conditions are changing, in part due to climate change, but also as a result of (firefighting) practices, probably the largest of which has been interrupting the natural cycle of fires. — Peter Fuglem
Three factors drive boreal forest fires, Flannigan says: ignition, weather and fuel.
About two thirds of fires are ignited by lightning strikes. Most of the worst fires come from lightning strikes in remote areas, which limits a rapid response. Human activity causes other fires but efforts are being made to limit this destruction with public education, fires bans and visitation bans on high-risk areas.
Warm weather also increases fire risk, an issue that is becoming more pronounced due to climate change, which has increased the length of the fire season in Alberta by about a month. Warmer temperatures bring more lightning, and the hotter it gets, the more moisture is readily sucked up into the atmosphere, leaving the woods and deadfall drier and more likely to ignite.
The most intense fires tend to happen on the hottest, driest days, Flannigan says.
“They are the ones that are extremely difficult to manage. If the fire is the size of my office, the crew can put it out easily. If the fire is the size of a football field and it’s hot, dry and windy and there are fuels, it’s a real challenge.”
The government is making some progress in dealing with fuel for fires. Part of the problem here springs from our success in quickly putting out most wildfires. The lack of fire has prevented the boreal forest from regenerating. In the 1970s Alberta forests had mostly young and immature trees. Now they have mostly mature or over-mature trees with more deadfall, leading to a greater risk for the most intense and catastrophic of fires.
“Forest conditions are changing, in part due to climate change, but also as a result of (firefighting) practices, probably the largest of which has been interrupting the natural cycle of fires,” says Peter Fuglem, a B.C. fire expert who helped write Canada’s national wildfire plan and the 2012 review after the Slave Lake fire.
“Wildfires used to remove fuel and also break up the landscape level forest into various ages and types, therefore reducing the likelihood of wildfire expansion.”
There’s been a move in recent decades to allow for “appropriate response” to wildfires, Flannigan says, which essentially means putting out fires quickly around human settlements, but monitoring them and letting them burn in more remote areas.
Another way to thwart a fire is to push fire preparedness. The Alberta government spends $15 million a year on its FireSmart program, which is aimed at getting communities and homeowners to take steps to remove fuel such as dead brush from around their homes. Houses are ignited in a fire because of small, airborne embers from the main fire igniting the bushes, fences and sheds next to the main residence.
Remove that fuel and a house has a greater chance of surviving a fire.
Since it’s known that conifer trees like Black Spruce are highly flammable, it may make sense to remove them from within two kilometres of forest towns and cities. Major fires will shoot embers for up to two kilometres away.
It would be a significant expense to do this tree removal, but Flannigan says: “The cost of doing that would be cheaper than what we’re going to pay for Fort McMurray.”
Even if all best practices are followed, however, a handful of Alberta’s 1,400 annual wildfires will rage.
Fort McMurray was set to burn by a dry winter, a quick spring melt and extremely hot temperatures and low humidity in late April and early May, before the deciduous trees had sprouted the leaves that cool the forest.
“Under those conditions it’s hard to say whether any type of mitigation would have helped,” Beverly says. “It may have been something that was just not avoidable … When you have communities embedded within a flammable forest landscape like the boreal, this is going to be an ongoing risk.”