Southern Sierra Nevada Projects

Areas for Action in Southern Sierra Nevada: California Spotted Owl and Fisher

California Spotted Owl Sheila WhitmoreCalifornia spotted owl and fisher are at-risk species that inhabit dense mature forests in the southern Sierra Nevada. Concerns about both species date back to the 1980s when low numbers or declining population trends were detected. Habitat alteration from logging and fire suppression were each identified as threats to these species.

CSO, a medium sized brown owl, is found throughout the Sierra Nevada bioregion, but demographic studies have concluded that populations are declining.

Image left: California Spotted Owl Sheila Whitmore

Image right: Pacific Fisher USFSPacific Fisher USFS

Fisher, a medium-sized brown mammal, occurs in several locations in California, but the native population in the Sierra Nevada is restricted to a small number of animals dispersed from Yosemite National Park south to the Kern Plateau. The conservation status of these species has been a concern to scientists, state and federal wildlife agencies, and conservation stakeholders. The fisher population in the southern Sierra Nevada was listed as a threatened ecologically significant unit (ESU) under the California Endangered Species Act in early 2019.

Presently, CSO and fisher are being considered for listing under the Federal Endangered Species Act by the US Fish and Wildlife Service with determinations for each expected in October 2019. Regardless of the outcome of these listing decisions, scientists and regulators agree that these species are at-risk and require additional measures to stabilize them.

Range of Each Species in California

Calif Spotted Owl Range

Range of Pacific Fisher

Maps taken from Guitierrez et al. (2017, for CSO) and Spencer et al. (2015, for fisher) See citation, below.


Too much high severity fire and poorly designed logging projects threaten the persistence of these species. Years of fire suppression led to the ingrowth of too many small trees causing forest habitat to become more uniform and simplified. This habitat is also much less resilient to drought, disease and beetle kill, and wildfire events during extreme weather conditions. Wildfire events, like the Rim Fire in 2014, have led to large areas of mature forest (greater than 3,000 acres) removed by high severity fire.

Fire History Stanislaus and Sierra NFs

Fire History Sequoia NF

Maps taken from Guitierrez et al. (2017) See citation, below.

High severity fire effects have always been a component of beneficial fire in this ecosystem, but such areas were generally less than 1,000 acres in size and most often less than 10-200 acres in size. These changes in the distribution of high quality habitat combined with logging projects that focus on removal of large trees have created conditions where there are not enough large trees with dense canopy cover to support nesting and denning for these species. Lack of periodic, beneficial fire has also reduced the diversity in the plant community that occupies the understory of the forest, and simplified habitat conditions. These changes, along with post-fire plantation forestry and its associated management activities and effects, have eliminated or lowered the quality of nesting and denning habitat, as well as reduced the quality of habitat for prey. 

Habitat to Support Fisher’s Movements

Habitat suitable for fisher’s denning, resting, and foraging occupies a fairly narrow elevational band. Fires that kill most of the trees can limit the movement of fishers. The recent fisher strategy recommends taking actions to limit fire severity to low and moderate, especially in key locations.

Habitat to Support Pacific Fisher SN

Key Areas for Action

SFL is focusing on three conservation action areas in the southern Sierra Nevada to improve conservation for California spotted owl and fisher, and to protect roadless areas. The first is the forest plan revision process for the Sierra and Sequoia National Forests. The second is a newly proposed project to complete a decision to support logging and prescribed fire on 1.5 million acres over fifteen years on the Stanislaus and Sierra National Forests. The third is a project in the South Fork Merced landscape, at the intersection of the Stanislaus National Forest, the Sierra National Forest and Yosemite National Park. Despite the devastating loss of human lives, property, and cost, the Ferguson Fire of 2018 resulted in fire effects that benefit the plant communities within much of its footprint. The fire can be considered to have accomplished a restoration objective in terms of reducing future fire hazards and improving habitat. We are looking at next actions that will leverage these benefits on this landscape. For each action area, our goals are to: 1) improve conservation of California spotted owl and fisher; 2) protect roadless areas for the benefit of California spotted owl, fisher, and biodiversity and ecosystem health more generally; 3) increase the use of managed fire for ecological benefit; and 4) sustain a diverse and strong voice for conservation.

Three Areas for Action in Southern Sierra

Map citations

Gutiérrez, R.J.; Manley, Patricia N.; Stine, Peter A., tech. eds. 2017. The California spotted owl: current state of knowledge. Gen. Tech. Rep. PSW-GTR-254. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 294 p. 

Spencer, W.D., S.C. Sawyer, H.L. Romsos, W.J. Zielinski, R.A. Sweitzer, C.M. Thompson, K.L. Purcell, D.L. Clifford, L. Cline, H.D. Safford, S.A. Britting, and J.M. Tucker. 2015. Southern Sierra Nevada fisher conservation assessment. Unpublished report produced by Conservation Biology Institute.

Inyo National Forest Plan Revision

Sequoia National Forest Plan Revision

Sierra National Forest Plan Revision