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International Journal of Wildland Fire International Journal of Wildland Fire Society
Journal of the International Association of Wildland Fire
RESEARCH ARTICLE (Open Access)

Future regional increases in simultaneous large Western USA wildfires

Seth McGinnis https://orcid.org/0000-0001-8082-834X A * , Lee Kessenich https://orcid.org/0000-0001-5954-9311 A , Linda Mearns A , Alison Cullen B , Harry Podschwit https://orcid.org/0000-0001-5776-486X C and Melissa Bukovsky https://orcid.org/0000-0001-6415-965X A
+ Author Affiliations
- Author Affiliations

A RAL/CISL, NCAR, Boulder, CO 80307, USA.

B Evans School of Public Policy & Governance, University of Washington, Seattle, WA 98195, USA.

C Oak Ridge Institute for Science and Education, Oak Ridge, TN 37831, USA.

* Correspondence to: mcginnis@ucar.edu

International Journal of Wildland Fire 32(9) 1304-1314 https://doi.org/10.1071/WF22107
Submitted: 27 June 2022  Accepted: 13 July 2023   Published: 1 August 2023

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Background: Wildfire simultaneity affects the availability and distribution of resources for fire management: multiple small fires require more resources to fight than one large fire does.

Aims: The aim of this study was to project the effects of climate change on simultaneous large wildfires in the Western USA, regionalised by administrative divisions used for wildfire management.

Methods: We modelled historical wildfire simultaneity as a function of selected fire indexes using generalised linear models trained on observed climate and fire data from 1984 to 2016. We then applied these models to regional climate model simulations of the 21st century from the NA-CORDEX data archive.

Key results: The results project increases in the number of simultaneous 1000+ acre (4+ km2) fires in every part of the Western USA at multiple return periods. These increases are more pronounced at higher levels of simultaneity, especially in the Northern Rockies region, which shows dramatic increases in the recurrence of high return levels.

Conclusions: In all regions, the models project a longer season of high simultaneity, with a slightly earlier start and notably later end. These changes would negatively impact the effectiveness of fire response.

Implications: Because firefighting decisions about resource distribution, pre-positioning, and suppression strategies consider simultaneity as a factor, these results underscore the importance of potential changes in simultaneity for fire management decision-making.

Keywords: climate change, climate change impact assessment, fire management, NA-CORDEX, regional climate modelling, simultaneous fire, statistical modelling, western USA, wildfire, wildland fire.


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