Large projected increases in area burned and wildfire frequency by 2050 in Utah, USA

Changes in wildfire regimes may disrupt ecosystem processes as wildfires burn larger areas or burn more frequently than the recent natural range of variability. The climatic drivers of wildfire behavior may change in strength, but these effects are not likely to be uniform across space and different vegetation types. Increased understanding of how weather and climate influence patterns of burn area and frequency across vegetation types may assist in better predicting and managing future wildfire regimes. We examined a dataset of all 1469 wildfires ≥40 ha from 1984 - 2021 in Utah, USA, and used antecedent daily weather data to analyze how temperature and aridity influenced fire area and frequency across forested and non-forested vegetation types. The number of days in a year when air temperature was ≥ 26.6 °C (80 °F) was the best predictor for area burned for forest (R² = 0.31) and non-forest ecosystems (R² = 0.31) in Utah. However, model skill was variable across vegetation types and models performed best for high-elevation forest ecosystems (R² = 0.27 to 0.32) relative to low-elevation, non-forest ecosystems (R² = 0.11 to 0.31). By 2050, warming trends in Utah may result in a 60% increase in area burned for forests and a 232% increase for non-forests. These results highlight a simple metric – temperature – that explains large portions of variability in burned area and correlates with fire season length. A simple temperature metric is a good match for the vegetation and fire season climate of Utah, which is generally dry. Our results suggest that a warmer future may bring widespread and vegetation-specific changes in wildfire regimes with large increases in area burned across most vegetation types.