Abstract
Fuel, aridity, and ignition switches were all on in 2017, making it one of the largest and costliest wildfire years in the United States (U.S.) since national reporting began. Anthropogenic climate change helped flip on some of these switches rapidly in 2017, and kept them on for longer than usual. Anthropogenic changes to the fire environment will increase the likelihood of such record wildfire years in the coming decades. The 2017 wildfires in the U.S. constitute part of a shifting baseline in risks and costs; meanwhile, effective policies have lagged behind, leaving communities highly vulnerable. Policy efforts to build better and burn better, in the U.S. as well as in other nations with flammable ecosystems, will promote adaptation to increasing wildfire in a warming world.
Highlights
Fuel, aridity, and ignition switches were all on in 2017, making it one of the largest and costliest wildfire years in the United States (U.S.) since national reporting began
We focus on three “switches” that all had to be in the on position to catalyze a major wildfire season: the ignition switch, the fuel switch, and the aridity switch [4]
We detail how substantial regions of the western U.S experienced the wettest winter followed by the warmest and driest periods in the observational record (Figure 1). These climate and weather extremes occurred against a backdrop of anthropogenic changes to the fire environment: substantial human-related ignitions, increased fuel loads from a century of fire suppression, climate change, and greater numbers of homes built in flammable landscapes
Summary
In 2017, the United States (U.S.) experienced its costliest wildfire season ever, with damages exceeding $18 billion, and its third largest fire season—by area burned—in nearly 60 years [1]. We detail how substantial regions of the western U.S experienced the wettest winter followed by the warmest and driest periods in the observational record (Figure 1) These climate and weather extremes occurred against a backdrop of anthropogenic changes to the fire environment: substantial human-related ignitions, increased fuel loads from a century of fire suppression, climate change, and greater numbers of homes built in flammable landscapes. Network) of the reported within andpreceding in the preceding seven days While officials their finaltheir designations based onbased all ofon the wildfires.
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