A novel methodology to assess fuel treatment effectiveness: application to California’s forests

Background: Fuel treatments are increasingly used to mitigate wildfire risks. Aims: Proposing a novel, scalable and transferable methodology, this study investigates which treatment is (more) effective at a regional scale. Methods: This research evaluates the effectiveness of fuel treatments in California forests using the Fuel Treatment Effectiveness Monitoring (FTEM) database, which provides a binary (yes/no) assessment of treatment efficacy based on a structured subjective evaluation process. Proposed methodology enables scaling up site-specific treatment outcomes to the regional level. Key results: 61% of treatment footprints that were intersected by a wildfire were effective at modifying fire behavior. Treatments that included wildland fire and/or fuel removal were more effective in modifying fire behavior (>70%) than those dominated by fuel rearrangement (49–54%). Even treatments with lower overall efficacy successfully modified fire behavior when applied at large scales. Fuel treatment effectiveness outcomes were robust under extreme weather conditions. Conclusions: Fuel treatments are an effective wildfire mitigation tool, even under a warming climate with intensified fire weather. The proposed methodology can be used to assess fuel treatment effectiveness in United States regions that do not have California’s extensive case studies. Implications: The choice of treatment options needs to be carefully considered as their effectiveness widely varies.