The hidden variable: Impacts of human decision-making on prescribed fire outcomes

This study investigates the key drivers influencing prescribed fire effects across 16 sites in northern and central California, with particular emphasis on how operational decisions by fire practitioners shape burn outcomes. Data from the California Prescribed Fire Monitoring Program revealed that prescribed fires reduced total fuel loads by an average of 60 %, with greater consumption of postfrontal smoldering fuels (coarse fuels, 65 %) compared to frontline spreading fuels (fine fuels, 49.0 %). Crown scorch height showed a strong relationship to crown base height (R² = 0.37-0.86), suggesting that practitioners use crown base height as a visual indicator to control fireline intensity and avoid crown damage. This relationship may partially explain fuel consumption patterns, as crown avoidance strategies can influence fire behavior and intensity. Additionally, we documented a compensatory relationship between live and dead fuel moisture content across burn seasons, indicating that practitioners strategically select burning windows that maintain fireline intensity within controllable parameters regardless of season. Our findings demonstrate that human decisions fundamentally modify prescribed fire behavior to maintain safety parameters, often constraining outcomes to conservative ranges that may compromise treatment effectiveness. Understanding and accounting for these human factors is crucial to encouraging a more effective use of prescribed fires in the future. We recommend that future research explicitly include operational parameters and practitioner decision-making processes in assessing prescribed fire science, balancing safety considerations with goals for ecological restoration.