How is fire likely to affect the most important human assets and natural resources on a landscape?
The spatial wildfire risk assessment uses four key components: probability, intensity, susceptibility, and relative importance to determine the risk of wildfire to important values. Wildfire ignition, spread, and intensity are simulated using the advanced FSIM modeling platform that runs thousands of iterations of a fire season using a distribution of local weather and fuel conditions. Once we have an understanding of fire likelihood and relative intensity, we turn to local experts and scientific literature to determine how each of the highly valued resources and assets (HVRAs) on a forest are likely to respond to the range of possible fire intensities. This effects-analysis allows the forest to incorporate both the positive and negative outcomes from fire exposure given the most likely fire intensity conditions. Finally, we work with agency line officers and our partners to prioritize the relative importance of HVRAs relative to each other.
By combining all four components we can begin to prioritize fuel treatments and other mitigation actions depending on the relative likelihood of fire exposure. For example, on a fire-adapted ponderosa pine forest with high fire probability and low fire intensity, fires tend to be a net benefit to ecosystems, wildlife, and watersheds. If these are the primary HVRAs in this area, then the net outcome from fire exposure would most likely be positive. Conversely, in areas with sensitive infrastructure such as the wildland-urban interface of southern California, where chaparral ecosystems have high burn probabilities and high fire intensities, fires tend to have very negative outcomes on HVRAs. The potential hazards and benefits of fire are weighted based on landscape management priorities to produce a map of wildfire risk that accounts for both human and natural resource values. The map of wildfire risk can be used to prioritize hazardous fuel treatments, determine candidate landscapes for fire restoration, and to engage landscape partners to help plan for fires.