Number of dry days drives the expansion of simulated future wildfire in the Florida flatwoods pyrome

Abstract Background Wildfire activity in the Southeastern United States is shaped by unique ecological and climatic conditions that differ markedly from those in other regions of the country. Despite increasing recognition of fire’s ecological importance and rising risks under climate change, regional-scale projections of wildfire behavior in the Southeast remain limited. In this study, we applied the Large Fire Simulator (FSim), a stochastic, spatially explicit fire behavior model, to simulate ignition, spread, suppression, and containment of wildfires within a Florida flatwoods pyrome under both historical and mid-century future climate scenarios. Simulations were driven by fire weather data from 9 downscaled Global Climate Models (GCMs). We evaluated burn probability, fire size, and the number of large fires, and identified key meteorological factors influencing fire dynamics. Results Simulation results showed substantial variation in projected burn probability across GCMs, with the majority indicating an overall increase. Stepwise regression analysis identified the number of extreme burn days (days when Energy Release Component (ERC) for fuel model G is above the 97th percentile of historical ERC) and the average length of burn blocks (consecutive days when ERC is above the 80th percentile of historical ERC) as the strongest predictors of both region-level burn probability and total area burned. Additionally, the number of burn days and extreme burn days (days when ERC is above the 80th percentile and 97th percentile of historical ERC, respectively) were significantly associated with the number of large fires. Relative humidity and precipitation, rather than temperature alone, emerged as the primary climatic factors that account for fire-conducive conditions. To simplify the interpretation of fire danger, we introduced a “dry day” metric based on thresholds of relative humidity and precipitation, which demonstrated strong predictive power for burn probability in this humid, fuel-rich region. Conclusions This study found that the number of dry days is the critical factor that accounts for wildfire activity in this region. Our results highlight the importance of incorporating uncertainties in future dry-day projections when developing long-term strategies for wildfire management and adaptation under changing climate conditions.