Spatial and temporal assessment of responder exposure to snag hazards in post-fire environments

Researchers and managers increasingly recognize enterprise risk management as critical to addressing contemporary fire management challenges. Quantitative wildfire risk assessments contribute by parsing and mapping potentially contradictory positive and negative fire effects. However, these assessments disregard risks to fire responders because they only address social and ecological resources and assets. In this study, we begin to overcome this deficiency by using a novel modeling approach that integrates remote sensing, field inventories, imputation-based vegetation modeling, and empirical models to quantify post-fire snag hazard in space and time. Snag hazard increased significantly immediately post-fire, with severe or extreme hazard conditions accounting for 47%, 83%, and 91% of areas burned at low, moderate and high-severity fire, respectively. Patch-size of severe or extreme hazard positively correlated with fire size, exceeding >20,000 ha (60% of our largest fire) 10-years post-fire when reburn becomes more likely. After 10 years, snag hazard declined rapidly as snags fell or fragmented, but severe or extreme hazard persisted for 20, 30 and 35 years in portions of the low, moderate and high-severity fire areas. Because forests are denser and wildfires burn with greater severity than historically, these hazardous conditions may represent novel management challenges where risk of injury or death to responders outweighs the benefits of directly engaging the fire. Mapping snag hazard with our methodology could improve situational awareness for both decision makers and fire responders as they mitigate risk during fire management. However, as more landscapes burn we anticipate increased responder exposure to extremely hazardous conditions, which may further entrench the wildfire paradox as fire managers weigh current response decisions with future challenges. Aligning land management objectives with wildfire management needs, in part by mapping responder exposure to snags and other hazards, could help overcome the wildfire paradox and produce desirable long-term outcomes. This research also demonstrates the importance of interdisciplinary collaboration to account for risk to all aspects of fire prone social-ecological systems as we learn to live with fire in rapidly changing environments.