WWETAC Projects

Project title: Modeling wildfire risk to spotted owl habitat in Central Oregon, USA

Principal Investigator: Alan A. Ager, Pacific Northwest Research Station, Western Wildland Environmental Threat Assessment Center, Prineville, OR


Collaborators: Mark Finney, Rocky Mountain Research Station, Missoula, MT, Helen Maffei, Deschutes National Forest, Bend, OR

Key Issues/Problems Addressed:
Natural disturbances, including wildfire, insects and disease, are a growing threat to the remaining late successional forests in the Pacific Northwest, and especially on the east side of the Cascades. These forests are a cornerstone of the region’s ecological diversity and provide essential habitat to a number of rare terrestrial and aquatic species, including the endangered northern spotted owl (Strix occidentalis caurina).

Setting and Approach:

This study demonstrated probabilistic risk analysis for analyzing the effect of fuel treatments on the loss of northern spotted owl habitat.  Spatially-explicit probabilities of habitat loss for fuel treatment scenarios were calculated on a 70,245 ha study area in Central Oregon as part of the Five Butte fuel management project on the Deschutes National Forest. . The study used wildfire simulation modeling to calculate burn probabilities, and the Forest Vegetation Simulator to build habitat loss functions.  Combining the outputs provided a way to estimate the probability of habitat loss (i.e. risk).  Five fuel treatment scenarios were then analyzed to measure the effect of management activities on the probability of habitat loss.

Key Findings:

  • A quantitative wildfire risk assessments was developed and demonstrated to measure potential wildfire impacts to a key wildlife species.
  • The effect of increasing treatment area was a non-linear decrease in wildfire-caused habitat loss (risk), with the most efficient treatment rates at about 20% of the landscape.
  • Fuels treatments on (20 percent) of the forested land resulted in a 44 percent decrease in the probability of spotted owl habitat loss averaged over all habitat stands.


The modeling framework developed in this study demonstrated the feasibility of quantitative risk analyses for examining a wide range of fuel management issues on fire prone forests.  The work also advances the application of quantitative and probabilistic risk assessment for habitat and species conservation planning.


Ager,A., Finney, M. Kerns, B., Maffei, H. 2007. Modeling wildfire risk to northern spotted owl (Strix occidentalis caurina) habitat in Central Oregon, USA. Forest Ecology and Management 246:45-56. (PDF, 606 KB)Owl Habitat Loss


Map of the Five Buttes study area showing the probability of owl habitat loss for two of the six treatment scenarios (TRT-0, TRT-20) analyzed in the study. The probability of loss is a subset of the burn probability, and is the probability of a fire with sufficient intensity to eliminate forest conditions required for owl habitat. From: Ager et al. 2007.

Project ID: FY07AA28