Physical Sciences and Mathematics Commons^™

Human-Related Ignitions Increase The Number Of Large Wildfires Across U.S. Ecoregions, R. Chelsea Nagy, Emily Fusco, Bethany Bradley, John T. Abatzoglou, Jennifer Balch

Environmental Conservation Faculty Publication Series

Large fires account for the majority of burned area and are an important focus of fire management. However, ‘large’ is typically defined by a fire size threshold, minimizing the importance of proportionally large fires in less fire-prone ecoregions. Here, we defined ‘large fires’ as the largest 10% of wildfires by ecoregion (n = 175,222 wildfires from 1992 to 2015) across the United States (U.S.). Across ecoregions, we compared fire size, seasonality, and environmental conditions (e.g., wind speed, fuel moisture, biomass, vegetation type) of large human- and lighting-started fires that required a suppression response. Mean large fire size varied by three …