The role of fuel treatments in mitigating wildfire risk

Climate change has led to longer fire seasons and more intense wildfires worldwide and has caused substantial economic and environmental impacts in recent years. This challenge motivates an improvement in fuel treatment to balance between wildfire risk reduction and ecosystem protection. While fuel treatments have been widely applied to reduce wildfire occurrence and spread for a long time, the relationship between their design and effectiveness in wildfire risk mitigation is still unclear, especially under the varying fire severity conditions. In this study, we targeted a fire-prone ecosystem in Southwest China as the study area and designed 17 fuel treatment scenarios based on the local fire prevention plan, which contains three treatments (firebreaks, prescribed burning, and thinning), four treatment intensities (% of area treated), and two treatment shapes (belt and block). Using percentiles of the seasonal severity rating (SSR) index, we divided the 2000-2020 fire seasons into three severity scenarios: low (<= 25th), normal (25th-75th), and high (>= 75th). Following a framework to assess the effectiveness of fuel treatments on wildfire risk mitigation, we found all designs showed significant effects on risk mitigation under the low and normal fire severity scenarios. The effectiveness of fuel treatments in mitigating wildfire risk of different values was found to be influenced by their intensity and shape. However, even the most intensive fuel treatment design considered in this study cannot reduce wildfire risk significantly at the landscape scale under the high fire severity condition, which suggested that other fire management measures might have to be integrated. This study combined scenario design and risk assessment to demonstrate the effectiveness of fuel treatments in mitigating wildfire risk under different fire severity conditions, and the results could be used to guide the design and implementation of landscape fuel treatments in the future.