A forest fire is a force of awe unlike any other, carrying with it one-part destruction, another-part healing. Forest fires are so emblematic that art, myth and poetry are used to parallel a forest fire’s role, in nature, with the events in our lives. In fire, there is an embodiment of radical change, sadness and growth through the future. Living in the Yukon, we can see first-hand the process of fire from the blackened remains of a forest, through fields of fireweed and onto lush forests of young trees straining towards the sun. But renewal doesn’t end with trees; more and more, research shows that fire creates spaces for growth in what appears, on the surface, to be only bleakness.
In the boreal forest, the towering spruce and pine trees have evolved to use forest fires to their advantage. In the dark understory of the forest, it’s very hard for a tree’s seed to find a space to germinate. It’s challenging for a seedling to find enough light, space and fertile ground, let alone evade the risk of disease and insects in the leaf litter. However, after a fire there is ample light and space for a seedling to grow. Species like lodgepole pine evolved clever cones that open only when exposed to fire. In the roaring heat of a forest fire, thousands of seeds are released and carried aloft on the swirling wind currents generated in a fire, to land on clear soil fed by the ash of the blaze.
But what other species see forest fires as an opportunity? Many insects follow the ash, heat and smoke to the site of a fire. A total of 60 known species of insects have been found with specialized sensory organs that allow them to see infrared from active fires, and allow others to detect smoke from vast distances away. Shockingly, many of these insects even arrive while the fire is still underway. Smoke flies form swarms, swirling in the plumes of smoke in perhaps the most-apocalyptic mating display on Earth. Despite efforts to observe smoke flies outside of fire, little is known about these elusive creatures hanging in the smoke. The cedar wood wasp is another example of a species largely observed by firefighters, rather than by biologists. This species is found to lay its eggs only in the still-smouldering wood of cedar and juniper trees. Other insects rely on fungi species that only emerge after a fire, in an even more complicated, two-step process.
But why run towards the flames rather than flee from them? I spoke to Aaron Bell, a PhD candidate at the University of Saskatchewan, who recently published research about beetle species seeking out recent burns to lay their eggs in. In that research they found that beetles that had laid their eggs in freshly burned soils were more successful than those that laid their eggs in unburned soils. They hypothesize that in the post-fire soil, the eggs’ predators are wiped out. The mites, spiders and parasites that would love to feast on the eggs are, for a moment, absent in these locations. Furthermore, the ash is effectively sterile, having killed many of the pathogenic fungi and bacteria that could infect the eggs. The still-warm ash of a fire is, for a brief moment, a safe nursery for their young. What Aaron told me was that he was surprised by how specialized the egg-laying behaviour of these beetles is. He said the beetles are using fire like a tool, which is fascinating to see an evolved strategy for a benefit in living in habitats prone to fire—rather than fleeing from it.
Like the trees themselves, these beetles rely on the conditions created by the fire; and like the forest, they suffer in the absence of fire. These beetles require the natural patchwork of burned and unburned forests to ensure they are close enough to travel to a fire when the time comes. However, as a result of climate change, the patterns and intensity of forest fires is changing. Like most of the impacts of climate change, we can’t predict which species will thrive in these new conditions. Will they be another casualty in the loss of biodiversity from our carbon addictions? As in our metaphors, a blaze can push us forward, towards growth, but perhaps too much fire can be unpredictable and can result in lasting damage.
