USA — Background The authors write that “in boreal forests, climate change may act upon fuels through increased evapotranspiration not compensated for by increasing precipitation, or increased frequency of extreme drought years due to more persistent and frequent blocking high-pressure systems,” both of which phenomena are typically predicted to lead to more and larger wildfires. In addition, they state that “earlier snowmelt and longer summer droughts with climate change [i.e., warming] could also expose forests to higher wildfire risk.” And so they could. But do they?
What was done In an attempt to answer this important question, Girardin et al. investigated “changes in wildfire risk over the 1901-2002 period with an analysis of broad-scale patterns of drought variability on forested eco-regions of the North American and Eurasian continents.”
What was learned The seven scientists report that their analyses “did not reveal widespread patterns of linear increases in dryness through time as a response to rising Northern Hemisphere temperatures.” Instead, they say that they “found heterogeneous patterns of drought severity changes that were inherent to the non-uniformly distributed impacts of climate change on dryness.” In addition, they note that “despite warming since about 1850 and increased incidence of large forest fires in the 1980s, a number of studies indicated a decrease in boreal fire activity in the last 150 years or so (e.g. Masters, 1990; Johnson and Larsen, 1991; Larsen, 1997; Lehtonen and Kolstrom, 2000; Bergeron et al., 2001, 2004a,b; Mouillot and Field, 2005).” And they say that “this holds true for boreal southeastern Canada, British Columbia, northwestern Canada and Russia.”
What it means With respect to this long-term “diminishing fire activity,” as they describe it, Girardin et al. state that “the spatial extent for these long-term changes is large enough to suggest that climate is likely to have played a key role in their induction.” And, interestingly, that role would appear to be one of reducing fire activity, which is just the opposite of what the world’s climate alarmists contend should occur. And to emphasize that point, and provide still more evidence for it, they state that “the fact that diminishing fire activity has also been detected on lake islands on which fire suppression has never been conducted provides another argument in support of climate control.”
References 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., 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.
Johnson, E.A. and Larsen, C.P.S. 1991. Climatically induced change in fire frequency in the southern Canadian Rockies. Ecology 72: 194-201.
Larsen, C.P.S. 1997. Spatial and temporal variations in boreal forest fire frequency in northern Alberta. Journal of Biogeography 24: 663-673.
Lehtonen, H. and Kolstrom, T. 2000. Forest fire history in Viena Karelia, Russia. Scandinavian Journal of Forest Research 15: 585-590.
Masters, A.M. 1990. Changes in forest fire frequency in Kootenay National Park, Canadian Rockies. Canadian Journal of Botany 68: 1763-1767.
Mouillot, F. and Field, C.B. 2005. Fire history and the global carbon budget: a 1� x 1� fire history reconstruction for the 20th century. Global Change Biology 11: 398-420.
Girardin, M.P., Ali, A.A., Carcaillet, C., Mudelsee, M., Drobyshev, I., Hely, C. and Bergeron, Y. 2009. Heterogeneous response of circumboreal wildfire risk to climate change since the early 1900s. Global Change Biology 15: 2751-2769.