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

The threat of west-side fires was put into focus when the Labor Day Fires burned more than 300,000 hectares in western Oregon and Washington. A new study led by the USDA Forest Service's Pacific Northwest Research Station examines the context surrounding the fires and offers insight into the history of large, high-severity fires.

Matthew Reilly, research forester and lead author of the study, said that the 2020 Labor Day Fires were a wake up call for the region. The goal of our study was to help understand how this event compared to past west-side fires so that we can help inform adaptation strategies for the future.

Drawing from a literature review, extensive historical data, and new analysis, Reilly and his co-authors explored five questions surrounding the 2020 Labor Day Fires: how the 2020 fires compared with historical fires in the region, the role of weather and Climate, the effects of forest management and pre- The 2020 fires were very similar to historical fires on the west side, both in terms of their timing and size and the cause of their rapid spread.

When you look at historical fire regimes at longer time scales, our findings suggest that these are normal for west-side landscapes. Some of the locations that burned in 2020 were the same ones that burned in the early 20th century.

Because of the abundant and productive forests on the west side, prescribed burning and fuels management will be less effective than they are on the east side. Their study found that fire weather conditions are as extreme as they were during the 2020 fires.

According to the study, we need very different approaches and strategies in west-side forests than we do in dry forests.

The study was conducted as part of the Pacific Northwest Research Station's ongoing West-side Fire Research Initiative, which was launched in 2019. The study's authors are from the Washington State Department of Natural Resources, University of Washington, Oregon State University, and USDA Forest Service's Pacific Northwest region.

There are highlights.

• The 2020 Labor Day Fires were much larger and more severe than others in the recent record, but they were remarkably consistent with many historical fires. Strong east winds and dry conditions are the common denominators in both large historical fires of the past and the 2020 fires.
• Forest management and fuel treatments are unlikely to influence fire severity in the most extreme wind-driven fires, like the 2020 Labor Day Fires. Pre-fire forest structure, largely the result of previous forest management activities, had little effect on burn severity when east winds were strong during the 2020 fires.
• Fuel treatments around homes and infrastructure may still be beneficial under low and moderate fire-weather conditions.
• Adaptation strategies for similar fires in the future in west-side communities might, instead, focus on ignition prevention, fire suppression, and community preparedness.

More information: Matthew J. Reilly et al, Cascadia Burning: The historic, but not historically unprecedented, 2020 wildfires in the Pacific Northwest, USA, Ecosphere (2022). DOI: 10.1002/ecs2.4070 Journal information: Ecosphere