Good fire, bad fire

Both wildfires and fire mitigation have a part to play in protecting forest biodiversity, writes Alice Palmer.

After a summer of wildfires, some are asking if alternative forest management policies could prevent future disasters. Photo from CTV.

In the classic film Bambi (1942), the off-set villain “Man” sets the forest alight, forcing the terrified forest animals to run for their lives. Forest fires can be terrifying for humans, too: the 2023 season has seen communities across Canada evacuated, with many homes destroyed. Tragically, there have even been some deaths.

Given the destruction caused by catastrophic wildfires in recent years, it may seem surprising that wildfire is actually a natural, healthy force on forest landscapes. Fires serve to “reset” ecosystems: removing the build-up of dead wood and other plant matter on the forest floor, creating openings in the landscape, and providing an opportunity for new growth. This process of death and rebirth reestablishes a diversity of different forest types across the landscape; in other words, it increases “landscape-level biodiversity”.

Many of BC’s – and indeed Canada’s – forest types have historically been prone to periodic wildfire. For example, historical records indicate the boreal forests (the large swath of forest running across northern Canada, from BC to Newfoundland and into the territories) burned every 40-120 years. Many tree species are specifically adapted to fire; for example, the serotinous (resinous) cones of lodgepole and jack pines require heat to soften and release their seeds. Moreover, the thick bark on mature Douglas-fir and ponderosa pine trees enables them to survive understory fires.

Prior to European contact, Indigenous peoples set fires intentionally. Cultural burning, as it is called today, was done for a variety of reasons. For example, fire can stimulate the growth of forage (for game species) and berries. Carefully-controlled fire could also be used to clear trails and reduce the risk of more serious wildfire around camps and villages.

Not enough fire can lead to too much fire

To recap, wildfire is a normal, healthy part of many forest ecosystems. But the extreme fire seasons that we have seen in recent years have definitely not been normal.

One obvious trigger of this increase in catastrophic fires is climate change. With a warmer climate, the fire season is starting earlier and finishing later. Drought risk is increasing. Climate change has also increased the prevalence of insect outbreaks, adding additional dead trees as fuel for out-of-control wildfires.

Perhaps counterintuitively, the other major cause of the recent rise in wildfire risk and intensity is actually lack of fire on the landscape. Beginning in the early 20th century, land management policy shifted to forest fire prevention and suppression. While this practice enabled more forests to grow to a harvestable age, it has also changed the forest’s structure over time. Without periodic fires to thin out the understory vegetation (including smaller trees), stands have become denser and organic matter has built up on the forest floor. Consequently, when fires do occur, the extra fuel makes them burn more intensely.

How can we reduce the risk of catastrophic wildfires?

To reduce the risk of wildfires growing out of control, we can attempt to mimic the effects smaller, less intense fires have on the landscape. The goals are basically twofold: to reduce the build-up of fuel on the forest floor, and (if necessary) to reduce stand density (number of trees per hectare) so that fires cannot as easily spread tree-to-tree. Fuel reduction can be done manually (i.e., by hand-piling the debris) or by “prescribed burns” – carefully managed, low-intensity fires. Stand thinning, the removal of small trees from a densely-grown stand, is done with logging machinery.

To date, the majority of wildfire mitigation projects in BC have been in the wildland-urban interface (WUI). For example, a combination of manual brush removal and stand thinning was used on the outskirts of Logan Lake. When the large Tremont Creek Fire threatened the townsite in 2021, having lower-risk conditions in the surrounding forest enabled firefighting crews to successfully protect the community.

Restoring biodiversity and improving safety

Active forest management activities, such as stand thinning and prescribed burns, may not look very “natural” at first glance. However, they do restore the type of forest conditions that would have occurred naturally following periodic, low-intensity wildfire: forests with more space between trees and less fuel on the ground. While these more “open” forests can still burn, fires are less likely to spread out of control.

Just as wildfire contributes to landscape-level biodiversity, landscape-level biodiversity (created either by wildfire or active forest management) can affect fire behaviour.

As our climate changes, how we manage our forests, and think about wildfire, will have to adapt.

Alice Palmer is a forest scientist and consultant based in Richmond, BC. To follow her work, check out her Substack here.

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