Learning from Wildfire Decision Support: large language model analysis of barriers to fire spread in a census of large wildfires in the United States (2011–2023)

Background: Barriers are the landscape features that firefighters leverage to stop wildfire spread. In the United States, decision-makers discuss barrier availability in a framework called the Wildland Fire Decision Support System (WFDSS). Aims: This study analyzes WFDSS text from 6630 large wildfires and examines the barriers identified. Methods: A large language model was trained and validated, then used to detect 13 different barriers. Burn scar and fuel treatment barriers were compared with their availability near each fire. Key results: Decision-makers recognize barriers on most wildfires (75%) and explicitly state when they are not present. Roads (42% of incidents), burn scars (26%) and natural fuel variability (25%) are the most common barriers. There is a strong relationship between the amount of burned area and the probability that it is identified as a barrier. The relationship between fuel treatment barriers and their availability is weak, but fuel treatments are recognized as barriers at lower landscape thresholds than burn scars. Conclusions: Prior wildfire yields more opportunities for stopping fire spread than fuel treatments. However, a smaller area must be treated than burned naturally before fire managers consider it a barrier. Implications: This study helps direct policy towards expanding useful barriers.