Effects of post-fire logging on California spotted owl occupancy

Abstract

In fire-adapted forest ecosystems around the world, there has been growing concern about adverse impacts of post-fire logging on native biodiversity and ecological processes. This is also true in conifer forests of California, U.S.A. which are home to a rare and declining owl subspecies, the California spotted owl (Strix occidentalis occidentalis). While there has been recent concern about the California spotted owl occupancy in large fire areas where some territories have substantial high-severity fire effects, the influence of post-fire logging on the California spotted owl occupancy has been investigated very little, leading to some uncertainty about interpretation of conflicting results in different large fires. Research has found these owls preferentially select high-severity fire areas, characterised by high levels of snags and native shrubs, for foraging in forests that were not logged after fire, suggesting that removal of this foraging habitat might impact occupancy. The authors assessed the effect of post-fire logging and high-severity fire, on occupancy of this subspecies in eight large fire areas, within spotted owl sites with two different levels of high-severity fire effects. They found a significant adverse effect of such logging and no effect of high-severity fire alone. These results indicate it is post-fire logging, not large fires themselves, that poses a conservation threat to this imperilled species. RESEARCH ARTICLE Launched to accelerate biodiversity conservation A peer-reviewed open-access journalChad T. Hanson et al. / Nature Conservation 24: 93-105 (2018) 94

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

“…This large fire occurred partly within the boundary of our long-term, demographic study area containing individually-marked California spotted owls. In addition, we (Jones et al 2016) found no effect of salvage logging on the owls, but Hanson et al (2018) claimed that the negative effects of the King Fire on spotted owls was due to salvage logging, not severe fire. Therefore, we developed this paper for two reasons.…”

“…Regarding the second question, while there is unanimous empirical support that predominately low-severity fires have little negative impact on owls (Bond et al 2002, Bond 2016, Ganey et al 2017, there are two general alternative findings about the effect of large, high-severity fires on owls: neutral/beneficial effects (e.g. Bond et al 2009Bond et al , 2016Lee et al 2012;Lee and Bond 2015;Hanson et al 2018) and negative effects (Comfort et al 2016;Jones et al 2016;Eyes et al 2017;Ganey et al 2017;Rockweit et al 2017) (see also below the section "The science of spotted owls and fire"). Determining which of these results is correct will influence how forest restoration proceeds within the range of the spotted owl.…”

“…A paper published recently in Nature Conservation (Hanson et al 2018) attempted to reverse the growing scientific consensus that large, high-severity fires can negatively impact spotted owl populations (Comfort et al 2016, Eyes et al 2017, Ganey et al 2017, Rockweit et al 2017, claiming instead that post-fire salvage logging-not high-severity fire-poses the key threat to owls in post-fire landscapes. While the analysis performed by Hanson et al (2018) included data from several recent large fires, a large portion of the discussion section of Hanson et al (2018) was devoted to re-interpreting and criticising our study published in Frontiers in Ecology and the Environment (Jones et al 2016). Jones et al (2016) demonstrated unambiguous negative effects of a large (~40,000 ha) high-severity fire, the 2014 King Fire, on a study population of spotted owls in the central Sierra Nevada, CA.…”

Spotted Owls and forest fire: a systematic review and meta‐analysis of the evidence

“…, Hanson et al. ). Because Spotted Owl studies typically characterize territory vegetation only in the breeding core area within 1.1 km of the nest, these studies ignore habitat changes and alterations in the year‐round home‐range area that can extend up to 5.9 km from the nest (Zabel et al.…”

“…Post-fire logging is likely to be partially responsible for some of the negative effects attributed to high-severity fire in the studies reviewed here (Tempel et al 2014, Jones et al 2016, Rockweit et al 2017, Hanson et al 2018. Because Spotted Owl studies typically characterize territory vegetation only in the breeding core area within 1.1 km of the nest, these studies ignore habitat changes and alterations in the year-round home-range area that can extend up to 5.9 km from the nest (Zabel et al 1992).…”