Effectiveness of Fuel Treatments for Mitigating Wildfire Severity: A Managerâ•’Focused Review and Synthesis

The 2008 Request for Applications from the Joint Fire Science Program called for a synthesis of the extant literature that addresses the effectiveness of fuel treatments. We employed a four‐ pronged approach to address this task, including several scoping exercises with land managers, a literature review, a meta‐analysis, and development of an online pictorial database. Background and Purpose Changes in land use and management over the last century or more have increased the vertical and horizontal continuity of wildland fuels in many areas of North America (Pyne 1982, but see Keeley and Fotheringham (2001) and Johnson and others (2001) for discussion of exceptions). This increase in fuel hazard is compounding with climate change (Brown and others 2004) and ex‐urban development (Cova and others 2004) to place ever more values at risk to wildfire damages. Land managers have responded to political demands for an expansion of efforts to mitigate fuel hazards (USDA Forest Service 2000), piquing the interest for more research into the effects and effectiveness of these activities (Botti and others 1998). Consequently, the volume of fuel treatment studies has expanded greatly over the past decade (Figure 1). The 2008 Request for Applications from the Joint Fire Science Program called for a synthesis of the extant literature that addresses the effectiveness of fuel treatments. While a number of traditional literature reviews have been compiled on this topic (Keeley and others 2009; Agee and Skinner 2005; Peterson and others 2005; Graham and others 2004; Carey and Schumann 2003; Fernandez and Botelho 2003, Greenlee and Sapsis 1996), reviews such as these are inherently qualitative. They are also prone to bias in selection and interpretation of findings and tend to over‐emphasize contradictory conclusions with inadequate attention to sources of variability (Cooper and others 2009). Since 1955 the medical sciences have relied instead on an alternative approach to research synthesis using the techniques of meta‐analysis (Stroup and others 2000). Meta‐analysis is a systematic and quantitative approach to research synthesis that provides a method for the combination and comparison of results from independent trials to assess the direction, magnitude, and consistency of reported responses (Cooper and others 2009). It is now commonly applied to ecological questions (Gurevitch and others 2001) and has been recently applied to the wildland fuels treatment literature, as well (Martinson 1998, Wan and others 2001, Kopper 2002, Boerner and others 2009, Kallies and others 2010, Youngblood 2010). Kopper and others (2009) conducted a meta‐analysis on the effects of prescribed fire on fuel reduction. The focus of this project was a meta‐analysis of the literature documenting fuel treatment performance in mitigating subsequent fire intensity and severity to assess the quantitative support for the current fuel management paradigm. Meta‐analysis allowed us to test the expectation that fuel treatment effectiveness will vary predictably in different types of vegetation and by the degree to which a less hazardous condition is created through reducing surface fuels, removing ladders, opening canopies, and selecting for fire resistance (Agee and Skinner 2005).