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New study offers insight into past—and future—of west-side wildfires

New study offers insight into past - and future - of wildfires on the west side

Smoke plume from the Riverside Fire at Mount Hood National Forest, Oregon, in September 2020. Credit: USDA Forest Service

When the 2020 Labor Day Fires set fire to more than 300,000 acres in two weeks in parts of western Oregon and Washington, they devastated communities and fully exposed the threat of fires on the western side. A new study led by the USDA Forest Service’s Pacific Northwest Research Station examines the context around the fires and offers insights into the historical role of large, very severe fires — and the future of wildfires — west of the Cascades.

“Without a doubt, the 2020 Labor Day fires were a major fire on many levels, and a wake-up call for the region,” said Matthew Reilly, research ranger and lead author of the study, which is published in the journal. Ecosphere† “The aim of our study was to help understand how this event compares to past fires on the western side so that we can help inform adaptation strategies aimed at preventing or mitigating similar events in the future.”

Based on a literature review, extensive historical data and new analyses, Reilly and his co-authors explored five questions surrounding the 2020 Labor Day Fires: how the 2020 fires compared to historical fires in the region, the role of weather and climate, the effects of forest management and pre-fire forest structure on burn severity, the effects of these fires on the western landscape and what can be done to adapt to similar fires in the future. In the end, they found that the 2020 fires were remarkably consistent with historic fires to the west, both in their timing and magnitude and the cause of their rapid spread: dry conditions coupled with strong easterly winds.

“Our findings suggest that these severe fires are normal for western landscapes when you look at historical fire regimes over longer timescales,” Reilly said. In fact, the researchers identified similar large historic fires in the early 20th centurye century under similar weather conditions — some even around Labor Day — in some of the same locations that burned in 2020.

Because of the abundant and productive forests characteristic of the western side and the driving role of extreme winds, conventional fire management tools used in dry forests, such as prescribed combustion and fuel management, are likely to be less effective in western side forests than in the western side. the east side. This is especially the case, their study found, when weather conditions during fires are as extreme as those during the 2020 fires.

“Our study indicates that we need very different approaches and adaptation strategies in western forests compared to those we use in dry forests,” Reilly said.

The study was conducted as part of the Pacific Northwest Research Station’s ongoing West-side Fire Research Initiative, which launched in 2019 to develop science-based tools to help resource managers respond to wildfire risks in west-side forests. The study’s co-authors are from the Washington State Department of Natural Resources, University of Washington, Oregon State University, and the USDA Forest Service’s Pacific Northwest Region.

Highlights

  • The 2020 Labor Day fires were much larger and more severe than other fires in the recent record, but they were remarkably consistent with many historic fires. Strong easterly winds and dry conditions are the common denominators in both large historic fires of the past and the fires of 2020.
  • Forest management and fuel treatments are unlikely to affect fire severity in the most extreme wind-induced fires, such as the 2020 Labor Day Fires. Pre-fire forest structure, largely the result of previous forest management activities, had little effect on the severity of the burns when easterly winds were strong during the 2020 fires.
  • Fuel treatments around homes and infrastructure can still be beneficial in low and moderate fire conditions.
  • Adaptation strategies for similar fires in the future in western communities could instead focus on ignition prevention, firefighting and community preparedness.

Many factors influenced the severity of burns from the devastating 2020 Oregon mega fires


More information:
Matthew J. Reilly et al, Cascadia Burning: The Historic, But Not Historically Unprecedented Wildfires of 2020 in the US Pacific Northwest, Ecosphere (2022). DOI: 10.1002/ecs2.4070

Provided by USDA Forest Service


Quote: New study provides insight into past and future of West Side wildfires (2022, June 25), retrieved June 25, 2022 from https://phys.org/news/2022-06-insight-pastand-futureof-west-side -wildfires.html

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