Old growth forests are a cherished resource within the Sierra Nevada, making them a high priority for mapping within a climate change refugia lens. Old growth forests provide important habitat and ecosystem function for a long list of valued species, not least of which is the Pacific Fisher. Having been extirpated from more than half of its range, the fisher population in the southern Sierra Nevada is one of only two remaining native populations in the state of California. Although it is no longer legal to trap this fur-bearing carnivore, the fisher population remains in a precarious position largely due to habitat loss: the old growth forests required by fisher are at risk due to climate and land use change, severe forest fires, and human development that compromises forest connectivity. Fisher appear to depend on many classic hallmarks of old growth forests, such as mature stands with a mix of large conifer and hardwood trees, complex structures that include varied tree age and size classes, multistory canopy, snags, coarse woody debris, and quality denning habitat offered by hollowed out trees like California black oak or sugar pine. 

Beyond fisher, the federally-endangered mountain yellow-legged frog and federally-threatened Yosemite toad are two priority wildlife species that benefit from old growth forests, which are composed of important tree species like giant sequoia, sugar pine, whitebark pine, red fir, and California black oak.

Focal Resources identified at November 8, 2019 workshop:

• Pacific Fisher (Pekania pennanti)

  • Denning habitat

  • Topographic features

  • Connectivity

• Yosemite toad (Anaxyrus canorus)

• Giant sequoia (Sequoiadendron giganteum)

• Sugar Pine (Pinus lambertiana)

• Whitebark Pine (Pinus albicaulis)

• Red Fir (Abies magnifica)

• Black oak (Quercus kelloggi)

• Big trees

• Hardwood

• Mixed conifer forest

• Sites resilient to drought and fire (with available water)

Potential Management Actions:

Based on the focal resources, workshop participants identified potential management actions such as:

• Targeted thinnings, prescribed fire, fuels reduction

• Connectivity maintenance

• Extra marijuana site enforcement and remediation   

• Fisher reintroductions to sites within and near refugia

  • Fisher kit reintroductions in Yosemite

  • Fisher reintroductions in Washington (Olympic, North Cascades, and Mount Rainier)

• Restoration (e.g. oak)

• Planting trees in areas that are currently unforested but projected to be forest refugia in the future, promoting hardwood component

• Incentives on private land within refugia to retain oaks; revise California Forestry Practice rules to require oak retention in identified refugia

• Promote high canopy cover (and multi-story canopy) in refugia, and promote more heterogeneity (and lower canopy cover) outside of refugia

• Limit infrastructure/road development that would compromise key connectivity areas between identified refugia

Data Gaps/Future Work:

• Data on private land (beyond timber owners, e.g., S. CA Edison)

• Data on topographic features habitat selection for Pacific Fisher

• Future connectivity and habitat modeling 

Current efforts, data, and partnerships that could support identification and mapping of refugia for Old Growth Forest: 

• USFS fisher habitat modeling and monitoring data

• Yosemite scat data

• Fire Return Interval Departure (FRID)

  • Example: Using FRID analysis to map spatial and temporal changes in fire frequency on national forest lands in California

• Climate water deficit data

• Historic vegetation maps

• Vegetation projections

• Topographic maps

• Fire/fuels MOU between USFS, CalFIRE, and many private timber landowners (spotted owl focus)

• Southern Sierra Nevada Fisher Working Group

• Conservation Biology Institute

• Southern Sierra Nevada Fisher Conservation Assessment and Strategy

• Dinkey Collaborative Group

• Southern Sierra Prescribed Fire Council

• Governor’s Forest Management Task Force -- Sierra geographic tree group

• Tree-mortality working group

From https://www.nps.gov/yose/learn/nature/fishers.htm

• Sugar Pine Fisher Project

• Kings River Fisher Project