WWETAC Projects
Project title: Modeling wildfire risk to spotted owl habitat in Central Oregon, USA
Status: Completed
Principal Investigator: Alan A. Ager, Pacific Northwest Research Station, Western Wildland Environmental Threat Assessment Center, Prineville, OR 97754
E-mail Contact: Alan Ager, aager[at]fs.fed.us
Collaborator: Mark Finney, Rocky Mountain Research Station, Missoula MT, Helen Maffei, Deschutes National Forest, Bend, OR
Summary: Late-successional forest reserves in the dry forests of the Pacific Northwest provide habitat to a number of terrestrial and aquatic species that contribute to the region’s ecological diversity, including the endangered northern spotted owl (Strix occidentalis). Although concern over old-growth forest ecosystems and spotted owl habitat largely arose from commercial timber harvest, managers and the public are increasingly concerned about old-growth forest and owl habitat loss from severe wildfire and other disturbances. Forest managers are actively engaged in mitigation projects such as fuel reduction using mechanical thinning and prescribed fire to reduce potential impacts from natural disturbances within late-successional reserves and maintain spotted owl habitat. These efforts could benefit from formal risk analyses to quantify wildfire risks and tradeoffs among different treatment strategies. In this research, we describe the use of a quantitative, probabilistic wildfire risk assessment methodology that defines risk as expected loss of owl habitat. Specifically, risk is calculated as the product of (1) the probability of a fire burning at a specific intensity and location, and (2) the resulting change in habitat condition. We analyzed the expected loss of spotted owl habitat on a 65,823 ha study area in central Oregon for six different fuel reduction scenarios that varied in intensity. Burn probabilities were estimated by simulating 1000 randomly-ignited wildfires. A habitat loss function was developed for each stand using a forest stand wildfire simulator. Results showed a nonlinear response in expected value with increasing treatment area. Fuel treatments on a relatively minor percentage of the landscape (20 percent) resulted in a 50 percent decrease in expected loss of owl habitat. Our modeling approach can be applied to many other forest values and can also include the benefits of wildfire at species locations and intensities. The methodology we used advances the application of quantitative and probabilistic risk assessment to wildfire risk management and fuel treatment planning.
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
