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Wildfires and Climate Change

Time to completion
3 min

Summary

Warmer weather and more frequent drought are expected to contribute to an increase in large wildfires in Canadian forests.

The Essentials

  • Fire activity in Canada varies significantly from year to year, but there is scientific evidence that the risk of wildfires is increasing.1,2
  • The fire season, which is the snow-free period during which almost all wildfires occur, has been getting longer in most of Canada over the last half-century.3,4
  • At the same time, the number of hot and dry days (“fire weather”) that allow wildfires to spread quickly has increased substantially.5 Lightning, which is responsible for about half of wildfire ignitions,6 has now become common in areas such as northern Canada, where it was previously rare.7
  • How humans affect wildfires is complex and largely misunderstood. Whereas people ignite more than half of the fires in Canada every year,6 they also extinguish many fires before they become large, and indirectly affect fire regimes by modifying the land cover.8 Fire activity may have increased due to a warmer and drier climate, but during this time period fire suppression has also become more effective, thereby potentially obscuring the relationship between climate change and wildfire.
  • The frequency of large and very large wildfires has increased in Canada over the last several decades.2 These larger fire sizes may be a result of increased fuel availability (because of longer intervals between fires due to suppression), hotter and drier fire weather in recent decades, and longer fire seasons.
  • The area burned by wildfires has increased significantly since 1959 and this increase is occurring mainly in western Canada in zones where there has been an increase in lightning-caused fires. In central and eastern zones, trends in lightning-caused fires and area burned have remained stable or decreased slightly.2
  • Projections of future fire weather are likely to amplify this trend, perhaps tripling the current burn rate in some areas.9, 10
  • Wildfires represent a major risk to communities located in wildfire prone areas,8 and have led to hundreds of community evacuations over the last few decades.11
  • The 2016 wildfire in Fort McMurray, Alberta, was the most costly natural disaster (in terms of insured losses) in the modern history of Canada.
  • Smoke from large wildfires has significant effects on human health. Exposure to smoke causes serious respiratory problems, sometimes leading to premature death. In 2017, 30% of Canadians were exposed to significant wildfire smoke, costing billions of dollars in health impacts.12
  • Wildfire trends cannot be accounted for by climate alone. The fire regimes we have observed over the last half-century have also been driven by the combined effects of changes in the natural environment, human activities (increased ignitions and suppression), and sheer chance. Changes that can affect fire incidence include, for example, fuel (i.e., flammable vegetation), ignitions and land use and fire suppression.2
  • Projecting future fire activity is an active area of research. Major knowledge gaps remain in our understanding:
    • How wildfires ignite and spread in forest stands disturbed by large insect outbreaks (such as mountain pine beetle or spruce budworm) — many of which are projected to become more common and geographically widespread as the climate warms — remains largely unresolved.
    • Flammability and potential fire behavior in the large and growing expanse of thawed permafrost in northern Canada is understudied, given the massive impact of these wildfires on carbon loss.13

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These fact sheets are based on text from Susan Hassol, and ClimateData.ca would like to acknowledge her contribution, as well as those from the Climate Research Division (Environment and Climate Change Canada), the Canadian Forest Service (Natural Resources Canada) and our regional climate service partners.

References

  1. Wotton, B.M. and Flannigan, M.D., 1993. Length of the fire season in a changing climate. The Forestry Chronicle, 69(2), pp.187-192.
  2. Jain, P., Wang, X. and Flannigan, M.D., 2018. Trend analysis of fire season length and extreme fire weather in North America between 1979 and 2015. International journal of wildland fire, 26(12), pp.1009-1020.
  3. Wang, X., M.-A. Parisien, S. W. Taylor, J.-N. Candau, D. Stralberg, G. A. Marshall, J. M. Little, and M. D. Flannigan. 2017. Projected changes in daily fire spread across Canada over the next century. Environmental Research Letters 12:025005.
  4. Stocks, B. J., J. A. Mason, J. B. Todd, E. M. Bosch, B. M. Wotton, B. D. Amiro, M. D. Flannigan, K. G. Hirsch, K. A. Logan, D. L. Martell, and W. R. Skinner. 2002. Large forest fires in Canada, 1959-1997. Journal of Geophysical Research: Atmospheres 107:8149.
  5. Veraverbeke, S., Rogers, B.M., Goulden, M.L., Jandt, R.R., Miller, C.E., Wiggins, E.B. and Randerson, J.T., 2017. Lightning as a major driver of recent large fire years in North American boreal forests. Nature Climate Change, 7(7), pp.529-534.
  6. Kirchmeier-Young, M. C., F. W. Zwiers, N. P. Gillett, and A. J. Cannon. 2017. Attributing extreme fire risk in Western Canada to human emissions. Climatic Change 144:365-379.
  7. Hanes, C., X. Wang, P. Jain, M.-A. Parisien, J. Little, and M. Flannigan. 2019. Fire regime changes in Canada over the last half century. Canadian Journal of Forest Research 49:256-269.
  8. Flannigan, M. D., K. A. Logan, B. D. Amiro, W. R. Skinner, and B. Stocks. 2005. Future area burned in Canada. Climatic Change 72:1-16.
  9. Boulanger, Y., Gauthier, S., Gray, D.R., Le Goff, H., Lefort, P. and Morissette, J., 2013. Fire regime zonation under current and future climate over eastern Canada. Ecological applications, 23(4), pp.904-923.
  10. Amiro, B.D., Logan, K.A., Wotton, B.M., Flannigan, M.D., Todd, J.B., Stocks, B.J. and Martell, D.L., 2005. Fire weather index system components for large fires in the Canadian boreal forest. International Journal of Wildland Fire, 13(4), pp.391-400.
  11. Wotton, B.M., Flannigan, M.D. and Marshall, G.A., 2017. Potential climate change impacts on fire intensity and key wildfire suppression thresholds in Canada. Environmental Research Letters, 12(9), p.095003.
  12. Parisien, M.A., Barber, Q.E., Hirsch, K.G., Stockdale, C.A., Erni, S., Wang, X., Arseneault, D. and Parks, S.A., 2020. Fire deficit increases wildfire risk for many communities in the Canadian boreal forest. Nature Communications, 11(1), pp.1-9.
  13. Beverly, J.L. and Bothwell, P. 2011. Wildfire evacuations in Canada 1980–2007. Natural Hazards, 59(1), pp.571-596.
  14. Matz, C.J., Egyed, M., Xi, G., Racine, J., Pavlovic, R., Rittmaster, R., Henderson, S.B. and Stieb, D.M., 2020. Health impact analysis of PM2. 5 from wildfire smoke in Canada (2013–2015, 2017–2018). Science of The Total Environment, p.138506.
  15. Héon, J., D. Arseneault, and M.-A. Parisien. 2014. Resistance of the boreal forest to high burn rates. Proceedings of the National Academy of Sciences 111:13888-13893.
  16. Boulanger, Y., M. Girardin, P. Y. Bernier, S. Gauthier, A. Beaudoin, and L. Guindon. 2017. Changes in mean forest age in Canada’s forests could limit future increases in area burned but compromise potential harvestable conifer volumes. Canadian Journal of Forest Research 47:755-764.
  17. Marchal, J., Cumming, S.G. and McIntire, E.J., 2020. Turning down the heat: Vegetation feedbacks limit fire regime responses to global warming. Ecosystems, 23(1), pp.204-216.
  18. Schuur, E.A., Bockheim, J., Canadell, J.G., Euskirchen, E., Field, C.B., Goryachkin, S.V., Hagemann, S., Kuhry, P., Lafleur, P.M., Lee, H. and Mazhitova, G., 2008. Vulnerability of permafrost carbon to climate change: Implications for the global carbon cycle. BioScience, 58(8), pp.701-714.