Megafire causes persistent loss of an old‐forest species

Abstract

Climate change and a long legacy of fire suppression are leading to an increased prevalence of ‘mega‐disturbances’ such as drought and wildfire in terrestrial ecosystems. Evidence for the immediate effects of these novel disturbances on wildlife is accumulating, but little information exists on longer term impacts to species and ecosystems. We studied the occurrence dynamics of an iconic old‐forest species, the spotted owl (Strix occidentalis), on a long‐term study area in the Sierra Nevada, CA, USA from 1989 to 2020 to evaluate their multi‐scale population response following a 2014 megafire (the ‘King’ Fire) that affected a portion of our study area. We found that extensive severe fire within spotted owl sites resulted in both immediate site abandonment and prolonged lack of re‐colonization by owls six years post‐fire. Sites that experienced high pyrodiversity – a mosaic of burn severities – were more likely to persist after the fire, but this effect was only apparent at finer spatial scales. A potentially confounding factor, post‐fire salvage logging, did not explain variability in the probability of either owls persisting at sites or sites becoming re‐colonized; effects could be attributed only to severe fire extent and pyrodiversity. Our study demonstrates the prolonged effects of severe fire on the occupancy of this forest‐dependent species, suggesting that forest restoration that reduces megafires could benefit spotted owls. Our work emphasizes that long‐term monitoring can offer surprising learning opportunities and provide unparalleled value for understanding and addressing emerging environmental concerns.

The conservation impacts of ecological disturbance: Time‐bound estimates of population loss and recovery for fauna affected by the 2019–2020 Australian megafires

“…This could be driven by variation among species in their exposure to other threats (e.g., the turtles and Blue Mountains water skink are strongly affected by threats unrelated to fire); the time taken for critical resources to recover for some species; and life‐history traits. For example, the greater glider and yellow‐bellied glider ( Petaurus australis ) both depend on large tree hollows, a resource that could be reduced for decades after severe fire (Haslem et al., 2011; Jones et al., 2021; Lindenmayer & Taylor, 2020; Parnaby et al., 2010). Both glider species had the highest estimates for local population loss at 1 week, 1 year and also at 10 years/three generations after fire.…”

“…As well as causing greater immediate impacts on species, these extensive, severe or rapidly spreading fires tend to leave fewer unburnt refuges within the fire footprint (Collins et al., 2021), constraining population recovery by both in‐situ reproduction and recolonization from elsewhere (Banks et al., 2017). Key resources, including habitat structures (e.g., large tree hollows, leaf litter, deep pools, submerged woody habitat) as well as food, can be rare for many years after such fires (Gresswell, 1999; Haslem et al., 2011; Jones et al., 2021). Therefore, megafires can cause large, sudden, and enduring changes in population size for affected species that need to be recognized swiftly by legislative and policy review to ensure that investment, management, and research activities are prioritized to reduce extinction risk.…”

Fire severity and its local extent are key to assessing impacts of Australian mega‐fires on koala (Phascolarctos cinereus) density

“…However, koalas did not persist in such locations where high severity fire dominated in our study (see below). Spotted owls in North America show stronger persistence in areas for up to 6 years post‐fire where there is a high pyrodiversity at fine scales (300–700 m radii; Jones et al., 2021).…”

Regulated timber harvesting does not reduce koala density in north-east forests of New South Wales

“…Annual monitoring of koala occupancy has taken place since 2015 ( https://www.dpi.nsw.gov.au/forestry/science/forest-ecology/koala-research-in-nsw-forests ). Monitoring is also relevant in relation to devastating wildfires, which are a significant threat to koalas in forests 30 , 37 , as is the case for other threatened species 38 , 39 .…”