Forest fuel reduction, spotted owls, and adaptive management of forests in the Sierra Nevada: Where are we?
Our role in the Sierra Nevada Adaptive Management Project (SNAMP) was to assess how fuels-reduction projects impact the California spotted owl (Strix occidentalis occidentalis), a focal management species on national forests in the Sierra Nevada. We were invited to participate in SNAMP after the size and location of our study area (northern SNAMP site) and the amount of our annual operating budget had been determined. We chose to measure owl demographic rates (adult survival, reproduction, site occupancy) by surveying the entire area multiple times each year, marking all territorial adults with color bands, and determining reproductive output at all owl territories. Our prior experience with a radiotelemetry study of owls in response to fuels-reduction projects suggested that radiotelemetery was not a feasible approach given the ruggedness of the SNAMP study area and the existing budget.
During the first field season, we quickly realized that very few owls were present within the SNAMP study area, so we expanded our surveys to cover a much larger area. We later collaborated with statisticians at UC-Berkeley to perform a power analysis for Before-After-Control-Impact occupancy studies. The power analysis led us to modify our study design to a retrospective study using additional data from our ongoing, long-term demography study area adjacent to the SNAMP study area. By doing so, we now had mark-recapture, reproduction, and occupancy data at 74 territories for all or part of the period from 1993-2012. We believed that the enlarged dataset (at both spatial and temporal scales) would enable us to obtain the necessary sample size to detect changes in owl demographic rates. However, we needed to reframe our study objectives to assess the impacts of multiple types of timber harvest, in contrast to a specific type of timber harvest (fuels-reduction projects under the 2004 Sierra Framework). All modifications to our original study design were presented to the other SNAMP scientists, managing agencies, and stakeholders in an open, transparent manner at public meetings. We concluded that future adaptive management of spotted owls, a species having large home ranges, will require the application of management treatments and monitoring over a much larger spatial scale than that encompassed by SNAMP. We suggest that this may be achievable using the spotted owl surveys conducted by U.S. Forest Service personnel each year throughout the Sierra Nevada if survey protocols and data collection can be standardized across all national forests.