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

Abstract

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.

Occurrence patterns of Black-backed Woodpeckers in green forest of the Sierra Nevada Mountains, California, USA.

“…Our findings suggest that Black-backed Woodpecker occurrence in green forest is far greater than has been suggested by others (Odion and Hanson 2013), though it is still much lower than what has been reported in burned forest in this region (Seigel et al 2012), a pattern that is consistent with findings for the species elsewhere in its range (Goggans et al 1989, Trebmlay et al 2009, Rota 2013. Their distribution in green forest varies based on forest type, physiographic parameters, and habitat conditions, some of which follow patterns found in burned forest in the region.…”

“…Their status and occurrence patterns in Sierra Nevada green forest are unknown, although small numbers of nesting pairs have been documented outside of areas that recently burned at moderate or high severity (Raphael and White 1984). The importance of this secondary habitat may be underappreciated by researchers and managers working to conserve this rare species at the southern extent of its range (Odion and Hanson 2013). …”

Effects of Fire and Commercial Thinning on Future Habitat of the Northern Spotted Owl

“…While much of the concern about fire and thinning in dry forests of the Pacific Northwest has focused on spotted owls, it may also apply to other biota associated with dense, old forests, including species of conservation concern, such as Pacific fisher (Martes pennanti pacifica), which research indicates may benefit from mixed-severity fire (Hanson 2013), the Northern Goshawk (Accipiter gentilis), and, following fire, the Black-backed Woodpecker (Picoides arcticus), which depends upon higher-severity fire in dense, older forest (Odion and Hanson 2013). Like the spotted owl, studies have documented that this woodpecker is also negatively affected by thinning (Hutto 2008).…”

“…To calculate rotations of severe fire in the forests of the study area, we used available fire data from a time period, 1996-2011, which includes exceptionally large, rare fire events. Our approach may be useful to managers interested in maintaining habitat for other species that rely on dense forests in fire-prone regions (Odion and Hanson 2013).…”

Sierra Nevada fire severity conclusions are robust to further analysis: a reply to Safford et al.

“…Recent studies have found that current rates of high-severity fire, including in frequent-fire forest types, are often substantially lower than historical rates (Odion and Hanson 2013;Baker 2014;Odion et al 2014; Hanson and Odion in press). This raises a conservation concern for the many rare and declining wildlife species positively associated with the unique, and highly biodiverse, habitat created by high-severity fire: 'complex early seral forest' -particularly given frequent post-fire logging of this habitat Hanson 2014).…”