A process for modeling short- and long-term risk in the southern Oregon Cascades

Abstract

Evaluating tradeoffs between the short- and long-term risks of different management scenarios in fire prone ecosystems is crucial to implementation of the National Fire Plan and the Healthy Forest Restoration Act (H.R. 1904). We demonstrate a process for conducting these relative risk assessments using models and data generally available via the public domain. Our risk assessment process integrates information about the ecological characteristics of the landscape, vegetation dynamics as related to different management scenarios, and fire modeling, to generate inputs for effects analyses on water temperature, peak flows, landslides, and northern spotted owls ( Strix occidentalis caurina). The process is demonstrated for current management with owl foraging emphasis and no management scenarios in a 325,000 ha landscape in southwestern Oregon. The current management with owl foraging emphasis scenario represents a reasonable portrayal of current land management policies and allocations with an emphasis on providing spotted owl foraging habitat across the landscape. The no management scenario portrays only vegetation dynamics as projected by a growth and yield model. Results from both management scenarios were subjected to fire and effects modeling. Simulation results indicated that risk metrics used in this demonstration were sensitive to the manner in which we described and attributed the landscape and our model formulations and thus, were useful measures for relative risk assessments. Model simulations demonstrated that the potential for uncharacteristic fire increased five-fold within the first 20 years under both management scenarios. The area burned by crown fire and uncharacteristic fire also increased over time for both management scenarios. Both management scenarios resulted in a decline of spotted owl habitat, with the current management with owl foraging emphasis scenario creating more unfavorable conditions. We attribute the relatively high long-term risk of the current management with owl foraging emphasis scenario to a combination of the large-scale passive management approach instituted on a substantial portion of the landscape (approximately 55% of the assessment area), the presence of plantation-based forestry (approximately 22% of the area), and by default, the limited opportunity to implement hazardous fuels reduction at a scale large enough to influence landscape-level fuel patterns. These preliminary results suggest that a spatially explicit, more aggressive hazardous fuels reduction management scenario, that may conflict with current land management policies and allocations, is needed to reduce the continuity of hazardous fuels and sustain healthy forest conditions and spotted owl habitat.