CANADA – Wildfires have broken many records in the western United States and Canada in the past three years, including the devastating fires that blackened large areas and burned hundreds of buildings in California, Oregon and Washington in September 2020.
However, wildfire is often at odds with human interests, because fires burn trees that might have otherwise been cut down by logging companies. In British Columbia, post-fire salvage logging is often used to recoup the economic losses that come with wildfire, by harvesting the logs for lumber, plywood and pulp.
Our research focused on the prey species that live in these forests — snowshoe hares, red squirrels, mice and voles — and are important food for owls, lynx, marten, fisher and coyotes. Salvage logging led to fewer prey species and lower prey abundances for up to a decade after the fire compared to prey populations in sites that were burned but not salvage logged.
We found that post-fire salvage logging removed nearly all standing trees from burned areas, making these sites unsuitable for snowshoe hares, red squirrels and southern red-backed voles. These species all need some vertical cover to shelter from predators. Salvage-logged areas supported almost exclusively deer mice, while post-fire regenerating stands had higher species diversity and higher vole populations.
Snowshoe hares and red squirrels recolonized forest sites within nine years of the fire. Snowshoe hare densities were higher in these forests than they were in mature forest sites, but red squirrels were only half as common. Salvage-logged sites, however, had no red squirrels or snowshoe hares nine years after the fire.
For example, in 2017, B.C. experienced its largest wildfire season in history, with more than 1.2 million hectares of forest burned. The following year, that record fell, with 1.3 million hectares burned. With that much land burned, there was a large potential for post-fire salvage logging to impact millions of hectares.
Post-fire salvage logging occurred on the Chilcotin Plateau study area following the large Hanceville Fire of 2017. Large wildfires and the intense post-fire salvage logging that follows those fires have the potential to shift small prey mammal populations across entire landscapes if this trend continues.
These massive shifts in prey base will almost certainly also affect the forest predators and raptors that require these small mammals as their prey, leading to a large shift in wildlife communities. In related work, we have seen that lynx, marten, fisher and coyotes all shift behaviour and abundance in relation to fires and post-fire salvage.
Given the importance that post-fire regenerating forests had for snowshoe hares, red squirrels and voles in our study, we stress the importance of policy decisions around post-fire forest management. At present, wildlife considerations are not fully included in post-fire forestry decisions.
Salvage logging was clearly detrimental to the majority of small mammals, and our results suggest that current post-fire practices should be changed.