Bad fire seasons can come in bunches, but so can quiet ones
B.C. has rarely seen a decade of wildfire damage like the one we have just lived through, with losses fuelled by record-shattering fire seasons in 2017 and 2018, with more than a 2.5 million hectares burned in just two summers.
That’s more than any decade in the past 100 years.
You have to look back to 1958 to find a year even close to being so catastrophic and to the 1920s for a decade that rivals the 2010s.
“Each year is a single case, but overall we’ve got to expect that our fire risk is increasing,” said associate professor David Scott, research chair in watershed management at UBC Okanagan. “We should expect larger areas to burn and that’s the big picture.”
The smaller picture is a bit more complex.
Although the general trend is toward hotter, dryer forests, clusters of bad fire seasons have historically been interrupted by cool, quiet periods that sometimes last four or five years at a time, according to data from the Ministry of Lands, Forests and Natural Resource Operations.
The summer of 2019 was a very quiet fire season, with less than 10 per cent of the area burned compared to the current 10-year rolling average.
The Earth’s temperature has been climbing since the 1850s, the end of a 500-year “little ice age.” Greenhouse gas emissions have recently accelerated that rise, said John Innes, dean of UBC’s faculty of forestry.
But in the near term, it’s possible B.C. could see a series of cooler summers and quieter fire seasons due to the potent influence of the El Niño-La Niña effect and the Pacific Decadal Oscillation, a recurring pattern of climate variability emanating from the mid-Pacific Ocean.
If both cycles tend toward cooling, their effect is intensified and relatively quiet fire seasons could “absolutely” be with us for a few years, he said. The combined effect could temporarily mask the local impacts of climate change.
The Oscillation has historically brought periods of warming and cooling lasting about 30 years, most recently as a cool period from 1945 to 1977, when it abruptly shifted to a warming trend that lasted until the late 90s.
That’s when things got confusing. Since 1999, the Oscillation has cycled from cool to warm every five or six years.
“People are suggesting that the cycle is speeding up, but we don’t have a long enough time series to say that things have changed that dramatically,” said Innes. “It looks like it is accelerating, but the eyeball test is not always reliable.”
B.C.’s weather patterns are also influenced by flows of warm and cool water along the West Coast of North America, which come at intervals of two to seven years. These El Niño-La Niña events last anywhere from months to years.
Innes said scientists aren’t sure what triggers the Oscillation. “We have a better idea of how the El Niño works, but it appears to be changing, too, which suggests we don’t understand it as well as we thought.”
Then there is The Blob. The 800-kilometre-wide “marine heat wave” was first detected in 2013 in the North Pacific and reappeared briefly last fall.
“It is dissipating,” he said. “We don’t know why it is there, but we do know it affects our weather.”
On top of everything we have anthropogenic climate change, which is accelerating warming trends all over the world.
So, what if things cool off for a while in B.C.?
“I would be concerned that people would forget that wildfire is a major risk,” said Innes.
“I would be very concerned that politicians — who work on fouryear cycles — might become less concerned about addressing climate change.”
It didn’t take very long for people to forget the 2003 fires in Kelowna and start building homes in risky areas, he noted. “The public’s memory is very short.”
B.C. has generally been very successful at fire suppression, which has led to increasing fuel loads in our forests.
Rather than pursue full suppression, the government adopted a modified response to wildfire in 2012 that allows fires to burn naturally and encourage a return to roomier forests that don’t burn as intensely.
The provincial government — through the Forest Enhancement Society of B.C. — has also encouraged communities to thin forests near urban areas.
Kelowna and area First Nations have thinned out the forest over 10 square kilometres to create a “shaded fuel break” that is designed to allow grass to burn up quickly but leave the forest intact.
Widespread damage by mountain pine beetle has left B.C. with around 18 million hectares of forests littered with dead trees through the Interior and greatly intensified wildfires over the past 10 years.
Sad to say, we are not close to running out of pine-ravaged forest, Scott said.
“It took some of it out, but there are still vast areas of pine-damaged forest left.”
The province has also shown foresight in the way it replants forests, taking seed stock from areas south of the replanting area and growing trees that will thrive as the warmer temperatures creep north, anticipating future climatic conditions.
“That way you get forests that are better adapted to hotter, dryer conditions,” said Scott.