by US Forest Service
When the 2020 Labor Day fires burned more than 300,000 hectares over two weeks in parts of western Oregon and Washington, they devastated communities and focused on the threat of West Side fires. A new study led by the US Department of Agriculture’s Pacific Northwest Research Station looks at the context surrounding the fires and provides insight into the historical role and severity of major fires – and the future of wildfires – west of the Cascades mountain range.
said Matthew Riley, a forestry researcher and lead author of the study, which was published in the journal Ecosphere. “The aim of our study was to help understand how this event compares to previous West Side fires so that we can help with adaptation strategies aimed at preventing or mitigating similar events in the future.”
Drawing on a literature review, comprehensive historical data, and new analysis, Riley and colleagues explored five questions about the 2020 Labor Day fires: how the 2020 fires compare 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, and the effects of these Fires on the West Side 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 the historical fires on the western side, both in terms of their timing, size, and reason for their rapid spread — drought conditions accompanied by strong easterly winds.
“Our findings suggest that these intense fires are normal for West Side landscapes when you look at historical fire systems on longer time scales,” Riley said. In fact, researchers have identified similar large historical fires in the early 20th century under similar weather conditions – some even burning on Labor Day – at some of the same locations that burned in 2020.
Due to the abundance and productivity of forests characteristic of the West Side and the driving role of high winds, it is likely that traditional fire management tools used in dry forests, such as prescribed burning and fuel management, are less effective in West Side forests than they are in the East Side. Their study found that this is particularly the case, when fire weather conditions are as severe as those seen during the 2020 fires.
“Our study indicates that we need very different approaches and adaptation strategies in the west side forests compared to those we use in dry forests,” Riley said.
The study was conducted as part of the Pacific West Side Fire Research Initiative, which was launched in 2019 to develop science-based tools to help resource managers respond to wildfire risks in West Side forests. Study co-authors are from the Washington State Department of Natural Resources, the University of Washington, Oregon State University, and the USDA Pacific Northwest.
- The 2020 Labor Day fires were much larger and more intense than others in the last record, but were remarkably consistent with many historical fires. Strong easterly winds and dry conditions are the common denominator in both the large historical fires of the past and the fires of 2020.
- Forest management and fuel treatments are unlikely to influence fire intensity in the most intense wind fires, such as the 2020 Labor Day fires. Forest structure prior to fires, largely as a result of previous forest management activities, had little effect on burn intensity when it was East winds are strong during the 2020 fires.
- Fuel treatments around homes and infrastructure may be useful under low and medium fire climate conditions.
- Adaptation strategies to similar fires in the future in West Side communities may focus, instead, on flare prevention, fire suppression, and community preparedness.
Matthew C. Ocean (2022). doi: 10.1002/ecs2.4070
Wildfire Today, articles published in September 2020 tagged Oregon or Washington.