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Title: Evaluating competing risks of wildfires and fuels management on forest carnivore populations.
Abstract: Natural resource managers are challenged with maintaining wildlife populations and reducing risks of catastrophic or dangerous wildfires. Carnivores are particularly sensitive to wildfires as their populations are often fragmented by logging, development, and road networks. A large wildfire could therefore further reduce and fragment populations that are already at risk. Example carnivores include Spotted Owl (Strix occidentalis) and the fisher (Martes pennanti).
As an example of this challenge is the Vegetation-Fire-Owl Project (https://sites.google.com/a/pdx.edu/vegetation-fire-owl/). Our team is actively investigating the role of wildfires and fuels management of Northern Spotted Owl (NSO) habitat and populations. This research is focused on the 'dry side' conifer forests of Oregon and Washington. Proposals to thin
forests to reduce wildfire risk in this area have been controversial, in part because fuel treatments could adversely affect NSO habitat. The NSO is associated with the types of dense, structurally complex forests often targeted for fuel reduction treatments. Such thinning could reduce the quality of NSO habitat. However, crown-replacing wildfires also threaten NSO habitat, potentially over much broader areas than the treatments intended to reduce wildfire risks. Another example is the management of fisher, an uncommon forest carnivore that could someday be listed under the Endangered Species Act, populations in the Sierra Nevada of California. We investigated the potential relative risks of wildfires and fuels treatments on this isolated fisher population. To do so, we coupled three spatial models to simulate the stochastic and interacting effects of wildfires and fuels management on fisher populations: a spatially dynamic forest succession and disturbance model, a fisher habitat model, and a fisher metapopulation model. We assessed the relative effects of fuel treatment rate, treatment intensity, and fire regime on simulated fisher population over 60 years.
We compared the immediate negative effects of fuel treatments to the longer-term positive effect of fuel treatment (via reduction of fire hazard) using structural equation modeling. Our simulations of fisher populations suggest that the direct, negative effects of fuel treatments on fisher population size are generally smaller than the indirect, positive effects of fuel treatments, because fuels treatments reduced the probability of large wildfires that can damage and fragment habitat over larger areas. Simulated fire regime had a large effect on our results with the largest net benefit of fuel treatments occurring when a more severe fire regime was simulated.
Our results, however, must be interpreted with caution. There was large uncertainty in our projections due to stochastic wildfires and fisher population dynamics. Our results demonstrate the difficulty of projecting future populations in systems characterized by large, infrequent, stochastic disturbances. Nevertheless, these coupled models offer a useful decision-support system for evaluating the relative effects of alternative management scenarios.
Future research will assess habitat quality for fisher and bobcat in southern Washington in order to inform future fisher reintroductions in this area. An extensive network of camera traps (see bear photo) helps informs these analyses.
People: Robert Scheller, Shiloh Halsey
Publications and Presentations:
Halsey, S.M., W.J. Zielinski, and R.M. Scheller. 2015. Modeling predator habitat to enhance reintroduction planning. Landscape Ecology 2:1-15.
Scheller, R.M. E. Haunreiter, R. Kennedy, P. Singleton. Projected dry forest landscape dynamics and the implications for Northern Spotted Owl habitat under alternative management scenarios. Invited Speaker at Symposium of The Wildlife Society 75th Annual Meeting. October, 2012. Portland, OR.
Scheller, R.M, W.D. Spencer, H. Rustigian-Romsos, A.D. Syphard, B.C. Ward, J.R. Strittholt. Improving carnivore management options using stochastic simulation models. International Association of Landscape Ecology Meeting. April, 2012, Newport, Rhode Island.
Scheller, R.M. Using stochastic simulation to support carnivore management. Invited Speaker at the Society for Northwest Vertebrate Biology Annual Meeting. March, 2012. Hood River, Oregon.
Scheller, R.M. Disturbance regimes, competing objectives, and the limits to science: Using stochastic simulation to support management decisions. Invited Speaker at the PSU Systems Science Seminar. February, 2012. Portland, OR.
Scheller, R.M. Disturbance regimes, competing objectives, and the limits to science: Using stochastic simulation to support management decisions. Invited Speaker at the Western Section of The Wildlife Society Annual Conference. February, 2012. Sacramento, CA.
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