MAJOR CANADIAN WILDFIRES CORRELATE WITH LARGE VOLCANIC EVENTS

Wildfires are a major ecosystems disturbance in North American forests and are considered critical to the existence of some primary boreal tree types including pine, spruce and aspen (Stocks et al., 2002). Several studies have highlighted interactions between climatic regime, soil type and topography along with vegetation type as being important factors that influence fire in natural systems (Ogden et al., 1998). A recent study by Stocks et al., (2002) reveals that 86% of Canadian fires in the 1990s were ignited by lightning strike, highlighting the importance of this phenomenon to Canada’s modern forest ecosystems. It is known that fire is extremely sensitive to weather and climate (Swetnam, 1993) where recent modeling of future fire activity suggests that increases in fire occurrence and severity might be expected in west central Canada in future years (Flannigan et al., 2000). This may in part by driven by increased lightning activity (Price and Rind, 1994). Volcanic eruptions are known to produce lightning strikes e.g. Mtn Spurr (Thomas et al., 2007) and it is known that volcanic induced cloud to ground lightning strikes can occur at considerable distances from an erupting volcano (McNutt and Davis, 2000). I show here that whilst the majority (70.5%) of Canadian wildfires (>200ha) between the years 1959-1996 can be linked to climatic factors, 71.4% of years of major fire activity show little relationship to climate variability but instead can be correlated with known large North American volcanic events.