Background
The authors note that "climate is an important factor that affects the length of the fire cycle," and that "many studies have shown that the frequency of fires (area burnt/year) can increase or decrease depending on climatic conditions." For the eastern boreal forest of Canada, for example, they report that "since the end of the Little Ice Age, warm and humid air masses have replaced the cold and dry ones that characterized the Little Ice Age," and that "this increase in humid air masses has caused fire conditions to decrease and the length of fire cycles [time between fires] to increase (Bergeron and Archambault, 1993; Girardin et al., 2004)."

What was done
In a further study of the subject, Lauzon et al. investigated the fire history of a 6480-km² area located in the Baie-Des-Chaleurs region of Gaspesie at the southeastern edge of Quebec, "using Quebec Ministry of Natural Resource archival data and aerial photographs combined with dendrochronological data."

What was learned
The Canadian researchers found that coincident with the 150-year warming that led to the demise of the Little Ice Age and the establishment of the Current Warm Period, there was "an increase in the fire cycle from the pre-1850 period (89 years) to the post-1850 period (176 years)," and that "both maximum and mean values of the Fire Weather Index decreased statistically between 1920 and 2003," during which period "extreme values dropped from the very high to high categories, while mean values changed from moderate to low categories."

What it means
In this particular part of the world, 20th-century global warming has led to a significant decrease in the frequency of forest fires, as weather conditions conducive to their occurrence have gradually become less prevalent and extreme.

References
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.

Girardin, M.P., Tardif, J., Flannigan, M.D. and Bergeron, Y. 2004. Multicentury reconstruction of the Canadian drought code from eastern Canada and its relationship with paleoclimatic indices of atmospheric circulation. Climate Dynamics 23: 99-115.