FORT MCMURRAY, Alta. — The fire that caused 80,000 people to evacuate their homes and affected the Canadian economy when it reduced oil production got a lot of attention in 2016.
It was slightly more than one year ago that residents of Fort McMurray, Alta., fled the flames that destroyed more than 2,500 homes and temporarily halted oilsands activity.
The event generated international news and outpourings of support across Canada.
The threat and partial destruction of a city, with its direct impact on people, made the 2016 fire a well-known event. Less widely known is the fact that wildfires are common in this region of northern Alberta.
On the recent Alberta Soils Tour in the Athabasca region, participants examined soil and forest rejuvenation at the 1995 Mariana Lake Fire, the 2002 House River fire and the 2011 Richardson fire, as well as 2016 Fort McMurray fire that came to be known as “The Beast.”
Fires are so common in the area that it hindered Fort McMurray citizens’ early attention to the monster that would eventually raze some of their homes.
“It’s a regular thing for us. We are desensitized to it,” said Jordan Redshaw, communications co-ordinator for the regional municipality of Wood Buffalo.
In hindsight, he marvels at initial thoughts that the 2016 fire was no big deal.
“This is totally normal for our community and this is the mentality that was one of our bigger challenges in terms of evacuating the community as a whole,” he said.
“There is that pre-existing sentiment that, ‘oh it’s normal for this area to have that.’ ”
For those studying forest and soil rejuvenation after fires, however, the Athabasca area and its many fires over the years form a rich study environment.
Brad Pinno, a research scientist with the Canadian Forest Service, is studying forest response to disturbance, including fire and reclamation. The Athabasca region is an ideal location for him and his team.
“One of the most interesting things we found was, looking at the Fort McMurray fire from last summer, we were able to go back there that same year and it was amazing just how quickly all of the vegetation came back,” said Pinno.
“Four months later there were 100,000 stems (of trembling aspen) per hectare and they were all about four feet high on average. That’s just an incredible response of nature to the fire. So clearly these plants are adapted to these types of disturbances.”
Extremely dry conditions last May allowed the fire to spread but heavy rainfall in late spring and fall gave trees and plants a quick start afterward.
“The vegetation just exploded after the fire,” said Pinno. “It was the perfect conditions for these trees to get established.”
Much of the burned area south of Fort McMurray now features aspen and jackpine. Aspen are the primary deciduous trees in the region and when their tops are burned, they regenerate from root suckers.
“They are genetically identical to the previous trees that were there because they’re all the same genetic type. Individual stems are all exactly the same tree, basically,” said Pinno.
In the case of Jack pine, fire burns the trees and heats the cones so they release their seeds and begin regenerating the forest. Both aspen and jackpine thrive on the full sunlight available after a fire.
Seeds held dormant in the soil also sprout after a fire and form an understory, although that depends on fire severity and how much it affected organic matter in the top soil layers.
“You can lose a lot of nitrogen from the site after a fire,” said Pinno.
“It also can change the pH balance. A lot of the ash that’s generated from fires is really high in base cations. The pH can go up and that can shift the other nutrients, so potentially after a fire you can get a decrease in available phosphorus.
“The other thing that happens is you get this big flush of decomposition after a fire. If there is organic matter left after a fire, it’s warmer and you get a lot more available water because the trees aren’t there sucking it up anymore, so you get this hotter, moister environment that’s really conducive to … decomposition.”
Luvisol soil in Alberta is conducive to growing trees, which is fortunate given the many losses to fire and oil extraction.
However, when fire occurs, new tree stands will burn hotter because their branches overlap at the canopy and they have branches extending to the ground.
The House River, Mariana Lake, Richardson and Fort McMurray fires all started in May and were likely all caused by humans. Such springtime fires spread quickly because aspen is not yet leafed out and thus burns more freely.
Studies of fire aftermath may also be at least partially applicable for use in reclamation from oil sands activity. Alberta’s reclamation goals are to return the land to a natural state of some kind after oil sands projects conclude.
“Whatever we can learn from the natural forest is a great benefit. If we look at the natural forest, we can really see if there’s some species or some attribute or some process that we’re just missing from our reclamation areas,” Pinno said.