New Research Reveals More Frequent Fires in Western Oregon Forests

Study challenges long-held beliefs about fire history in Douglas fir forests

Published on Feb. 9, 2026

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New research led by a University of Oregon ecologist suggests that fire was historically more frequent in the Douglas fir forests of the western Oregon Cascade Range than previously believed. The study, which used tree-ring analysis to reconstruct fire histories, found that two-thirds of the sites investigated experienced multiple fires between 1300 and 1850, challenging the notion that these temperate rainforests had long fire-free periods.

Why it matters

The findings have important implications for how forest managers approach fire in the region, especially as fire seasons expand across the Pacific Northwest. The research suggests that the high-severity fires and long fire-free periods seen over the last century are not necessarily typical for the region, and that the complex old-growth forests are actually the product of multiple, lower-severity fires over time.

The details

The study, published in the journal Ecosphere, analyzed 667 wood samples from 36 sites on the west slopes of the Oregon Cascades, including areas within the Mount Hood and Willamette National Forests. The researchers used chainsaws to cut the tops off old-growth stumps and examined the fire scars preserved within the tree rings, which serve as a record of the forest's fire history. They found a total of 412 fire scars that documented 129 different fire years, suggesting it's fairly rare for the sites to go hundreds of years without fire.

  • The study analyzed fire records dating back to as early as the 1100s.
  • The researchers found that two-thirds of the 36 sites investigated reburned multiple times between 1300 and 1850.

The players

James Johnston

A landscape and fire ecologist at the University of Oregon's Institute for Resilient Organizations, Communities, and Environment, and the lead author of the study.

University of Oregon

The institution where Johnston is based and where the research was conducted.

U.S. Forest Service

A collaborator on the research project.

Oregon State University

A collaborator on the research project.

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What they’re saying

“We live in one of the moistest parts of the world, so we don't think of fire as being an important influence in this neck of the woods. But in fact, Douglas fir forests historically experienced a lot of fire.”

— James Johnston, Landscape and fire ecologist (Mirage News)

“It's not the absence of fire that makes these old-growth forests so stupendously complex. It's the occurrence of low- and moderate-severity fires, which don't kill all - or even most of - the trees, that open gaps in the canopy and stimulate understory vegetation and new trees in the hundreds of years that follow.”

— James Johnston, Landscape and fire ecologist (Mirage News)

What’s next

The researchers plan to continue studying these forest systems and work with local organizations to develop new management strategies that can help sustain these ecosystems in the face of future changes, such as warmer and drier fire seasons.

The takeaway

This research challenges long-held beliefs about the fire history of Douglas fir forests in western Oregon, suggesting that these forests have historically experienced more frequent, lower-severity fires than previously thought. This new understanding will help forest managers develop more effective strategies for adapting to the changing climate and fire regimes in the region.