For decades we have been making our forests more flammable — on purpose! Of course, this wasn’t the intention.
The intention was to grow a healthy crop of conifers for our forest industry. But to do so, industry and government found it necessary to eliminate broadleaf trees from our forests, which aren’t deemed profitable enough to keep around.
In the central interior of BC, and across the boreal forests of Canada, the primary forest type that has been eliminated to encourage the growth of conifers is made up of trembling aspen. Unfortunately for our forests’ fire resistance, trembling aspen are hard to light on fire.
According to work by Steve Cumming et al, from 2001, over a 36-year period the burn rate of pine forests was 840% higher than aspen. Black spruce forests were even more flammable while white spruce were slightly less. Put another way, for every 100 hectares of pine that burn, only 11.9 hectares of aspen would burn, assuming both forest types are equally distributed on the landscape.
Importantly, this study included those times of year when aspen are relatively flammable – spring and fall, before or after aspen have leaves. Forest fires are generally most severe mid-summer, when aspen have leaves. And when aspen have leaves, they are incredibly fire resistant.
The fire resistance of green aspen is well illustrated by a Canadian Forest Service study observing a raging crown fire moving through the treetops of a spruce stand in extreme fire conditions. When the fire encounters a stand of aspen, it stops dead. According to the Canadian Wildfire Behaviour Prediction Manual, green aspen aren’t expected to burn except in the driest, most severe drought conditions, and even then they aren’t expected to burn well.
Conifer-centric forestry is deeply ingrained in our wood-hewing national psyche
To be effective against wildfire, stands of aspen cannot be mixed with conifers. Mixed stands of even three-quarters aspen are still much more likely to burn than a stand of pure aspen. It’s that 25% conifer in the mix that allows things to light up.
And herein lies the problem. Forestry rules across most of BC limit pure aspen stands to 5% of a regenerating cutblock. There is no minimum, so if a company wants to spray 100% of the aspen with herbicide, they sure as heck can. In coastal BC this rule applies to many fire resistant species like alder, maple, birch, and cottonwood, especially on Douglas fir tree farms.
This is sheer stupidity, but it is because conifer-centric forestry is deeply ingrained in our wood-hewing national psyche. It’s what they teach in forestry school. It’s what we glorify in the photo essays of that all-Canadian rite of passage, tree planting. It was never the intention to create tinderbox forests that are exponentially more likely to catch fire, but we now live in a reality where wildfires are worse than any time in our past.
With new realities, it’s time we reappraise our values. Let’s embrace those weedy old broadleaf species.
James Steidle grew up in Prince George and studied at SFU after which he worked in the Legislative Assembly prior to becoming a self-employed woodworker. He currently spends his free time advocating for aspen and broadleaf forests as part of his Stop the Spray BC campaign: www.stopthespraybc.com
