Fuels reduction can directly improve spotted owl foraging habitat in the Sierra Nevada

Wildfire has been an important force in shaping biological diversity in forests of western North America. Patterns of reburning helped to maintain heterogenous landscapes with low tree densities that naturally limited the extent of severe stand-replacing fires. However, anthropogenic impacts over the past two centuries have dramatically altered fire activity and its ecological function, creating conditions that promote large and intense fires with no historical analog. Fuels reduction treatments represent proven methods to mitigate extreme fire events, but there is controversy over their potential effects to sensitive wildlife species. The California spotted owl (Strix occidentalis occidentalis) is a forest species that evolved under a frequent-fire regime. Controversy over how spotted owls may be impacted by fuels reduction is one of numerous contributing factors that has limited the pace and scale of implementation. To examine the relationships between spotted owls and fuels reduction treatments, we studied breeding season nocturnal foraging habitat selection related to fuel structural metrics of 159 GPS-tagged California spotted owls across the Sierra Nevada bioregion. Spotted owls selected for higher canopy base height, lower ladder fuel density, and lower canopy bulk density, which represent synergies between fuels reduction treatments and owl space use. Spotted owls also selected for higher surface fuels and higher canopy layer counts, representing potential trade-offs between fuels reduction goals and spotted owl space use. We overlaid the probability of space use by foraging spotted owls with relative stand density index (SDI), a measure of forest resilience, to classify Sierra Nevada landscapes into four groups: low management priority (low owl use/high forest resilience), fuels reduction priority (low owl use/low forest resilience), potential conflict zones (high owl use/low forest resilience), and habitat retention priority (high owl use/high forest resilience). Fuels reduction priority (34.4%) was the largest category, suggesting that potential impacts of fuels reduction on spotted owl foraging habitat may be less widespread in the Sierra Nevada than previously believed. Our results suggest that fuels reduction treatments, especially those focused on mutually beneficial goals such as increasing canopy base height, reducing ladder fuels, and reducing canopy bulk density may directly improve spotted owl foraging habitat while also mitigating the effects of large and severe wildfires on forest species and forest ecosystems.