Rapid Growth of Large Forest Fires Drives the Exponential Response of Annual Forest-Fire Area to Aridity in the Western United States

C S Juang; A P Williams; J T Abatzoglou; J K Balch; M D Hurteau; M A Moritz

doi:10.1029/2021GL097131

Rapid Growth of Large Forest Fires Drives the Exponential Response of Annual Forest-Fire Area to Aridity in the Western United States

Geophys Res Lett. 2022 Mar 16;49(5):e2021GL097131. doi: 10.1029/2021GL097131. Epub 2022 Mar 8.

Authors

C S Juang^{1

2}, A P Williams^{1

3}, J T Abatzoglou⁴, J K Balch^{5

6}, M D Hurteau⁷, M A Moritz⁸

Affiliations

¹ Lamont-Doherty Earth Observatory of Columbia University Palisades NY USA.
² Department of Earth and Environmental Sciences Columbia University New York NY USA.
³ Department of Geography University of California, Los Angeles Los Angeles CA USA.
⁴ Management of Complex Systems Department University of California, Merced Merced CA USA.
⁵ Earth Lab Cooperative Institute for Research in Environmental Science University of Colorado Boulder Boulder CO USA.
⁶ Department of Geography University of Colorado Boulder Boulder CO USA.
⁷ Biology Department University of New Mexico Albuquerque NM USA.
⁸ Cooperative Extension Division of Agriculture and Natural Resources & Bren School of Environmental Science & Management University of California, Santa Barbara Santa Barbara CA USA.

Abstract

Annual forest area burned (AFAB) in the western United States (US) has increased as a positive exponential function of rising aridity in recent decades. This non-linear response has important implications for AFAB in a changing climate, yet the cause of the exponential AFAB-aridity relationship has not been given rigorous attention. We investigated the exponential AFAB-aridity relationship in western US forests using a new 1984-2019 database of fire events and 2001-2020 satellite-based records of daily fire growth. While forest-fire frequency and duration grow linearly with aridity, the exponential AFAB-aridity relationship results from the exponential growth rates of individual fires. Larger fires generally have more potential for growth due to more extensive firelines. Thus, forces that promote fire growth, such as aridification, have more potent effects on larger fires. As aridity increases linearly, the potential for growth of large fires accelerates, leading to exponential increases in AFAB.

Keywords: climate change; database; drought; extremes; western US; wildfires.

Associated data

Dryad/10.5061/dryad.sf7m0cg72