Megafire effects on spotted owls: elucidation of a growing threat and a response to Hanson et al. (2018)

Abstract

The extent to which wildfire adversely affects spotted owls (Strixoccidentalis) is a key consideration for ecosystem restoration efforts in seasonally dry forests of the western United States. Recently, Jones et al. (2016) demonstrated that the 2014 King Fire (a “megafire”) adversely affected a population of individually-marked California spotted owls (S.o.occidentalis) monitored as part of a long-term demographic study in the Sierra Nevada, California, USA because territory occupancy declined substantially at territories burned at high-severity and GPS-tagged spotted owls avoided large patches of high-severity fire. Hanson et al. (2018) attempted to reassess changes in territory occupancy of the Jones et al. (2016) study population and claimed that occupancy declined as a result of post-fire salvage logging not fire per se and suggested that the avoidance of GPS-marked owls from areas that burned at high-severity was due to post-fire logging rather than a response to high-severity fire. Here, we demonstrate that Hanson et al. (2018) used erroneous data, inadequate statistical analyses and faulty inferences to reach their conclusion that the King Fire did not affect spotted owls and, more broadly, that large, high-severity fires do not pose risks to spotted owls in western North American dry forest ecosystems. We also provide further evidence indicating that the King Fire exerted a clear and significant negative effect on our marked study population of spotted owls. Collectively, the additional evidence presented here and in Jones et al. (2016) suggests that large, high-severity fires can pose a threat to spotted owls and that restoration of natural low- to mixed-severity frequent fire regimes would likely benefit both old-forest species and dry forest ecosystems in this era of climate change. Meeting these dual objectives of species conservation and forest restoration will be complex but it is made more challenging by faulty science that does not acknowledge the full range of wildfire effects on spotted owls.

The effect of scale in quantifying fire impacts on species habitats

“…They also suggest that areas with high habitat suitability for nesting may be more prone to high-severity fire, and that both relationships are strongest at large spatial scales. These results generally support previous analyses suggesting that large high-severity fires may threaten spotted owls and their habitat (Jones et al 2016;Jones et al 2019;Rockweit et al 2017). They also suggest that efforts to reduce the risk of high-severity fire in owl nesting habitat, including activities such as prescribed fire, managed fire, and fuels-reduction treatments, should be cautiously explored, especially when placed strategically around, but not necessarily in, nesting habitat, to reduce risk of high-severity fire within the nesting habitat (e.g., US Department of Interior 2012;Waltz et al 2014;Roccaforte et al 2015;Chiono et al 2017;Ziegler et al 2017).…”