A century of transformation: fire regime transitions from 1919 to 2019 in southeastern British Columbia, Canada

Abstract

ContextIn fire-excluded forests across western North America, recent intense wildfire seasons starkly contrast with fire regimes of the past. The last 100 years mark a transition between pre-colonial and modern era fire regimes, providing crucial context for understanding future wildfire behavior. ObjectivesUsing the greatest time depth of digitized fire events in Canada, we identify distinct phases of wildfire regimes from 1919 to 2019 by evaluating changes in mapped fire perimeters (>20-ha) across the East Kootenay region (including the southern Rocky Mountain Trench), British Columbia. MethodsWe detect transitions in annual number of fires, burned area, and fire size; explore the role of lightning-and human-caused fires in driving these transitions; and quantify departures from historical fire frequency at the regional level. ResultsRelative to historical fire frequency, fire exclusion has created a significant fire deficit in active fire regimes, with a minimum of 1-10 fires missed across 46.4-percent of the landscape. Fire was active from 1919 to 1939 with frequent and large fire events, but the regime was already altered by a century of colonization. Fire activity decreased in 1940, coinciding with effective fire suppression influenced by a mild climatic period. In 2003, the combined effects of fire exclusion and accelerated climate change fueled a shift in fire regimes of various forest types, with increases in area burned and mean fire size driven by lightning. ConclusionsThe extent of fire regime disruption warrants significant management and policy attention to alter the current trajectory and facilitate better co-existence with wildfire throughout this century.

Wildfire evacuation patterns and syndromes across Canada's forested regions

“…Over the last 150 years, the fire regime of interior British Columbia has shifted from relatively frequent fires ignited by lightning and Indigenous stewardship, to burning associated with mining and livestock grazing activities of early European settlers from the late 19th to early 20th century, followed by active fire suppression since the 1940s (Baron et al, 2021; Brookes et al, 2021). Using thinning and prescribed burning to break up areas of continuous, dense forest and restore some of the historical landscape heterogeneity might reduce the potential for rapidly growing crown fires that have led to evacuations (Daniels et al, 2011; Klenner et al, 2008).…”

Guiding principles for transdisciplinary and transformative fire research

“…Cultural burning, an intentional type of landscape fire, has been conducted by Indigenous peoples across BC for millennia for diverse purposes, including managing preferred food species, promoting wildlife habitat, reducing risk of negative impacts from uncontrolled fires, and to fulfill an obligation to care for the land (Turner et al 2000;Gottesfeld 1994; Lake and Christianson 2019; Lewis et al 2018;Dickson-Hoyle et al 2022;Xwisten Nation et al 2018;Christianson et al 2022). This burning was spatiotemporally heterogeneous and, combined with lightning ignitions, created a patchwork mosaic of ecosystem structure and composition (Copes-Gerbitz et al 2023;Hoffman et al 2017) that limited impacts of subsequent fires (Brookes et al 2021;Baron et al 2022).…”

“…This past century of excluding and suppressing both lightning-ignited fire and Indigenous fire and land stewardship practices, coupled with climate change, is driving increasing fire size and severity and associated impacts to societies and ecosystems (Fig. 2) (Abbott and Chapman 2018;Hanes et al 2019;Coogan et al 2019;Baron et al 2022).…”

“…For example, our methodological expertise ranges from qualitative inquiry and participatory action research (Dickson-Hoyle and John 2021;Copes-Gerbitz et al 2021;Burr 2022), to mapping and modeling (Baron et al 2022;Crowley et al 2019aCrowley et al , b, 2022Kitchens et al 2022), to field-based forest assessments (Copes-Gerbitz et al 2023; Dickson-Hoyle et al: Fire severity drives understory community dynamics and the recovery of culturally significant plants, accepted manuscript; Baron et al: Fuel types mismatch forest structure and composition in interior British Columbia: a way forward, accepted manuscript), and to historical analyses (Sutherland et al 2023;Copes-Gerbitz et al 2022b). Drawing from these different methodologies has helped many of us understand and address the complexity (Principle 1) of landscape fire through our research, as well as develop new understandings of the fire challenge in BC.…”

Fire severity drives understory community dynamics and the recovery of culturally significant plants

“…These challenges are particularly prevalent throughout western North America, where increasing evidence points to the role of over a century of fire suppression, exclusion of Indigenous peoples and their fire stewardship practices, and timber-oriented forest management in disrupting historical fire regimes (Hagmann et al, 2013(Hagmann et al, , 2021Knight et al, 2022;Levine et al, 2022). In BC, these impacts followed European colonization from the mid-1800s and have resulted in widespread fire deficits across many forest ecosystems (Baron et al, 2022;Hagmann et al, 2021;Parisien et al, 2020). Many fire scientists and land managers are now advocating the need to "restore fire-resilient landscapes" (Hessburg et al, 2015), including through the restoration of historical fire regimes (Hagmann et al, 2021).…”