U.S. Joint Fire Science Program


Date of this Version


Document Type



Final Report JFSP Project Number: 09-1-10-7


US government work.


The extent and severity of fires in the United States during the last decade has been remarkable. Since 2002, there has been seven years (2002, 2004, 2005, 2006, 2007, 2011, 2012) when over 2.8 million ha have burned, more than twice the previous decade. The extent of recent fire activity has increased risks to lives and property (Cohen 2008; , biodiversity and species-at-risk (Spies et al. 2006), the timber value of forests (Butry et al. 2001) and forests as a carbon sink (Hurteau et al. 2008, 2011). Although one driver of the increase in fire extent, at least in western forests, is climate change (Westerling et al. 2006), human agency in the form of fire management has significantly contributed to the severity and extent of recent wildfires. Since the turn of the 20th century federal forest fire policy has emphasized fire suppression and the policy has been very successful at reducing the area burned by fire until the most recent decade (Pyne 1982; Stephens and Ruth 2005; Miller et al. 2009a). The effect of fire suppression on fire activity in western forests is geographically variable and can be generalized based on knowledge of fire regimes prior to fire suppression. Fire regimes characterize the cumulative effect of temporal and spatial patterns of fire behavior and fire effects on vegetation and ecosystems over a specified period of time, usually centuries (Agee 1993; Brown 2000). Fire suppression has had little effect on fire regimes in wet or cold forests that historically burned at high severity at intervals of 200-400 years (Agee 1993; Morgan et al. 2001; Schoennagel et al. 2004). On the other hand, suppression of fire in dry pine and mixed conifer forests that once experienced frequent (every 5-30 years) low-moderate severity surface fire has led to an increase in forest density and the quantity and continuity of surface and canopy fuels (e.g. Covington and Moore 1994; Skinner and Chang 1996; Taylor 2000; Beaty and Taylor 2007; Fule et al. 2009; Skinner et al. 2006a,b; van Wagtendonk and Fites-Kaufman et al. 2006). The increase in surface and canopy fuel has increased the risk of high severity fire and high severity fire effects, and area burned at high severity has recently increased in the southern Cascades and Sierra Nevada in California (Miller et al. 2009a).The severity of recent wildfires is a concern to fire and resource managers in California and other western states (Fried et al. 2004; Fulé et al. 2004) and has led to shifts in forest management (i.e. Healthy Forest Restoration Act 2003) to emphasize reduction of surface and canopy fuels to reduce the potential for high severity fire (Agee and Skinner 2005; Schmidt et al. 2008).