Le Goff, H., Flannigan, M.D., Bergeron, Y. and Girardin, M.P. 2007. Historical fire regime shifts related to climate teleconnections in the Waswanipi area, central Quebec, Canada. International Journal of Wildland Fire 16: 607-618.
In An Inconvenient Truth, Al Gore says "wildfires are becoming much more common," stating there has been a "steady increase in major wildfires in North and South America over the last five decades" and "on every other continent as well," due to concurrent global warming. This being the case -- in the world according to Al -- one might expect that almost everywhere on earth there would be evidence of an increase in fire frequency between the coldest periods of the Little Ice Age and the peak warmth of today, if the real world were anything like the one imagined by Gore.
What was done
In a study that sheds important new light on this subject, four Canadian forest scientists investigated "regional fire activity as measured by the decadal proportion of area burned and the frequency of fire years vs. non-fire years in the Waswanipi area of northeastern Canada [49.5-50.5°N, 75-76.5°W], and the long-term relationship with large-scale climate variations ... using dendroecological sampling along with forest inventories, aerial photographs, and ecoforest maps."
What was learned
Le Goff et al. report that instead of the interval of time between wildfires shortening as time progressed and the climate warmed -- as was implied by Gore to have been almost universal -- there was "a major lengthening [our italics] of the fire cycle." How major, you ask? There was a lengthening, in their words, "from 99 years before 1940 to 282 years after 1940." In addition, the four researchers note that "in the context of the past 300 years, many regional fire regimes of the Canadian boreal forest, as reconstructed from dendroecological analysis, experienced a decrease in fire frequency after 1850 [or the "end of the Little Ice Age," as they describe it] (Bergeron and Archambault, 1993; Larsen, 1996) and a further decrease after 1940 (Bergeron et al., 2001, 2004a,b, 2006)."
What it means
Clearly, the world according to Al is not the world in which we live.
Bergeron, Y. and Archambault, S. 1993. Decreasing frequency of forest fires in the southern boreal zone of Quebec and its relation to global warming since the end of the "Little Ice Age." The Holocene 3: 255-259.
Bergeron, Y., Gauthier, S., Kafka, V., Lefort, P. and Lesieur, D. 2001. Natural fire frequency for the eastern Canadian boreal forest: consequences for sustainable forestry. Canadian Journal of Forest Research 31: 384-391.
Bergeron, Y., Flannigan, M., Gauthier, S., Leduc, A. and Lefort, P. 2004a. Past, current and future fire frequency in the Canadian boreal forest: Implications for sustainable forest management. Ambio 33: 356-360.
Bergeron, Y., Gauthier, S., Flannigan, M. and Kafka, V. 2004b. Fire regimes at the transition between mixedwood and coniferous boreal forest in northwestern Quebec. Ecology 85: 1916-1932.
Bergeron, Y., Cyr, D., Drever, C.R., Flannigan, M., Gauthier, S., Kneeshaw, D., Lauzon, E., Leduc, A., Le Goff, H., Lesieur, D. and Logan, K. 2006. Past, current, and future fire frequencies in Quebec's commercial forests: implications for the cumulative effects of harvesting and fire on age-class structure and natural disturbance-based management. Canadian Journal of Forest Research 36: 2737-2744.
Larsen, C.P.S. 1996. Fire and climate dynamics in the boreal forest of northern Alberta, Canada, from AD 1850 to 1985. The Holocene 6: 449-456.Reviewed 5 March 2008