Projected increases in western US forest fire despite growing fuel constraints

Escalating burned area in western US forests punctuated by the 2020 fire season has heightened the need to explore near-term macroscale forest-fire area trajectories. As fires remove fuels for subsequent fires, feedbacks may impose constraints on the otherwise climate-driven trend of increasing forest-fire area. This study tests how fire-fuel feedbacks moderate near-term (2021-2050) climate-driven increases in forest-fire area across the western US. Assuming constant fuels, climate-fire models project a doubling of forest-fire area compared to 1991-2020. Fire-fuel feedbacks only modestly attenuate the projected increase in forest-fire area. Even models with strong feedbacks project increasing interannual variability in forest-fire area and more than a two-fold increase in the likelihood of years exceeding the 2020 fire season. Fuel limitations from fire-fuel feedbacks are unlikely to strongly constrain the profound climate-driven broad-scale increases in forest-fire area by the mid-21st century, highlighting the need for proactive adaptation to increased western US forest-fire impacts.

John T. Abatzoglou, David S. Battisti, A. Park Williams, Winslow D. Hansen, Brian J. Harvey, Crystal A. Kolden