Restoring dry forests in the Pacific Northwest, shaped by frequent low-intensity fire and widely spaced trees, often means thinning dense stands that accumulated after decades of fire suppression. This can make forests healthier and more resilient to wildfire, but it can raise concerns about protecting wildlife that depend on dense tree cover, including the northern spotted owl.
A new study by researchers at Oregon State University and the U.S. Forest Service and just published in Forest Ecology & Management, suggests that restoration of landscapes that historically burned frequently through planned, controlled fire does not have to conflict with spotted owl conservation.
The study, led by Jeremy Rockweit, a postdoctoral student at Oregon State, identified forest areas used by the northern spotted owl for nesting and roosting that were more and less likely to persist through fire. They have now incorporated their findings into maps that could help land managers decide what areas of the landscape would benefit from a light or heavy-handed approach to forest restoration.
"This research is important for land managers trying to better balance wildlife conservation and forest restoration, and shows that protecting spotted owls and restoring fire‑resilient forests don't have to be competing goals," said Rockweit, who prior to earning his doctorate at Oregon State spent 17 years monitoring spotted owls in California and Oregon.
Before European settlement, western U.S. landscapes adapted to frequent fire were shaped and sustained by repeated burning. At this time, areas that previously burned at lower severity tended to reburn at lower severity and areas previously burned at higher severity tended to reburn at higher severity.
Historically, topography played a key role in determining fire severity levels. Sheltered locations near drainage bottoms often burned less frequently or at lower severity, supporting denser stands of closed-canopy, older forests. Upper slope areas, which are more exposed, burned more frequently or at higher severity.
During the last century, fire suppression has allowed dense, closed canopy forests to expand, including to these upper slope locations and today's landscapes are less resilient and resistant to fire. This has happened at a time when fire seasons are getting longer, hotter and drier.
In the Pacific Northwest, northern spotted owls, a federally threatened species that for decades have been at the center of controversy over balancing conservation and timber production, tend to nest and roost in closed-canopy forest. Recent increases in wildfire activity in the spotted owl's range has become the most significant threat to old forests used by spotted owls, research has found.
For the new study, researchers combined long-term spotted owl monitoring data beginning in the 1980s and data mapping fires from 1985 to 2022 to identify "fire refugia" for spotted owls. Fire refugia are locations within a burned landscape that burn less frequently or severely than the surrounding area because of their position in the landscape. They can be thought of as "islands," where old forest structure can be sustained through multiple fires to help species and biodiversity survive.
The research focused on two regions: the eastern Cascades in Washington and the Klamath in southwestern Oregon and northwestern California. The research team modeled past fires that occurred under what researchers called moderate and extreme fire weather conditions, with the different level determined by temperatures and wind speeds at the time of the fires.
They found that forest suitable for spotted owl nesting and roosting was more likely to persist through fire when it occurred in those sheltered locations, whereas nesting and roosting forest was least persistent when it occurred higher upslope, such as along ridgetops. These patterns were consistent across both regions.
"Our maps could be used by managers to plan restoration-based activities that benefit landscape resilience and spotted owl conservation because spotted owls in these regions appear to benefit from some amount of habitat heterogeneity," Rockweit said.
Under extreme fire conditions, the study found that both regions are expected to lose suitable spotted owl nesting and roosting habitat.
"These insights have important implications for land managers and shift the focus from a desire to retain as much nesting and roosting forest as possible to one of recognizing the inherent value of ecologically and topographically diverse landscapes for spotted owls," Rockweit said.
Co-authors of the paper are Meg Krawchuk, Oregon State College of Forestry; David Bell, U.S. Forest Service Pacific Northwest Research Station; Katie Dugger, Oregon State College of Agricultural Sciences; and Damon Lesmeister, Oregon State and U.S. Forest Service Pacific Northwest Research Station.
