image: Noisy Creek Fire of 2017 burning Washington's Colville National Forest. view more
Credit: Image credit: Flickr/National Interagency Fire Center.
A study examines the upslope advance of forest fires in the United States. Fire is integral to the maintenance of forests. However, in recent decades, fire size, the length of fire seasons, and the number of fires have increased in the western United States. Forest fires have also advanced upslope, extending the fire territory to previously wet areas. Mojtaba Sadegh and colleagues examined records of forest fires larger than 405 hectares that occurred between 1984 and 2017 across 15 mountainous ecoregions of the western United States. Since 1984, high-elevation fires have advanced upslope by 252 meters. Upslope advance was greater for high-elevation fires than for fires at low elevations. The extent of burnt area also increased at a greater rate at high elevations--where fire and anthropogenic activity have been historically rare--than at dry, low elevations colocalized with human settlements. The primary cause of high-elevation fires was lightning, whereas low-elevation fires mainly resulted from anthropogenic activity. The authors also found a significant relationship between high-elevation fires and increased aridity during warm seasons. Global warming has reduced the high-elevation flammability barrier, making an additional 81,500 square kilometers of forested land across the western United States susceptible to fires. The findings suggest that climate change largely contributed to increased fire activity in the United States, according to the authors.
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Article #20-09717: "Warming enabled upslope advance in western US forest fires," by Mohammad Reza Alizadeh et al.
MEDIA CONTACT: Mojtaba Sadegh, Boise State University, ID; tel: 949-272-6429; email: <mojtabasadegh@boisestate.edu>
Journal
Proceedings of the National Academy of Sciences