Data and code from: Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires

Higuera, P.E., M.C. Cook, J.K. Balch, E.N. Stavros, A.L. Mahood, and L.A.
St. Denis. 2023. Shifting social-ecological fire regimes explain
increasing structure loss from Western wildfires. PNAS Nexus 2: In Press.
Structure loss is an acute, costly impact of the wildfire crisis in the
western United States (“West”), motivating the need to understand recent
trends and causes. We document a 246% rise in West-wide structure loss
from wildfires between 1999–2009 and 2010–2020, driven strongly by events
in 2017, 2018, and 2020. Increased structure loss was not due to increased
area burned alone. Wildfires became significantly more destructive, with a
160% higher structure loss rate (loss/kha burned) over the past decade.
Structure loss was driven primarily by wildfires from unplanned
human-related ignitions (e.g. backyard burning, power lines, etc.), which
accounted for 76% of all structure loss and resulted in 10 times more
structures destroyed per unit area burned compared to lightning-ignited
fires. Annual structure loss was well explained by area burned from
human-related ignitions, while decadal structure loss was explained by
state-level structure abundance in flammable vegetation. Both predictors
increased over recent decades and likely interacted with increased fuel
aridity to drive structure-loss trends. While states are diverse in
patterns and trends, nearly all experienced more burning from
human-related ignitions and/or higher structure loss rates, particularly
California, Washington, and Oregon. Our findings highlight how fire
regimes – characteristics of fire over space and time – are fundamentally
social-ecological phenomena. By resolving the diversity of Western fire
regimes, our work informs regionally appropriate mitigation and adaptation
strategies. With millions of structures with high fire risk, reducing
human-related ignitions and rethinking how we build are critical for
preventing future wildfire disasters.