Projecting Impacts of Fire Management on a Biodiversity Indicator in the Sierra Nevada and Cascades, USA: The Black-Backed Woodpecker

ABSTRACT

In the Sierra Nevada and southern Cascade ranges of California and Oregon, a genetically distinct population of the black-backed woodpecker has become rare due, in part, to fire suppression. This species is considered an indicator species for its primary habitat: early successional burned forests with an abundance of standing dead trees. Fuel reduction treatments such as post-fire logging, and forest thinning prior to fire (by creating insufficient snag density and enhancing fire suppression), may further reduce this habitat, but this has not been quantified. Our goal here is to address this information gap. Specifically, we first quantified the impacts of fire suppression and fuel treatments on primary habitat for the black-backed woodpecker. Our objective in this paper was to address how fire management affects the primary habitat of the black-back woodpecker and associated species in the Sierra Nevada and Cascades. We found that fire suppression was associated with a dramatic reduction in stand-initiation processes, a proxy for tree mortality, since the 1930s on public lands. We additionally found that thinning and post-fire clear cutting each exacerbated the effects of fire suppression by reducing primary habitat at an approximately 1:1 ratio with area treated. A scenario based on thinning 20 percent of mature forests over a 20 year period, and post-fire logging in 33% of potential habitat created by fire, reduced the amount of primary habitat after 27 years to 30%of the amount that would occur without these treatments, assuming that modeled effects of the fuel treatments in controlling fire may be realized. Our results indicate that conserving the distinct population of black-backed woodpeckers in the southern Cascades and Sierra Nevada and the biodiversity for which they are an indicator will require that more unthinned area be burned by wildfires and protected after fire as critical habitat. Our results also show that restoration of fire to an extent closer to historical levels would considerably increase black-backed woodpecker habitat and have minimal tradeoff with conservation of mature forest.

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