U.S. Joint Fire Science Program


Date of this Version


Document Type



FInal Report Project ID: 08-1-1-19


US government work.


One of the key uncertainties in fuels treatments is their longevity under a changing climate. Several recent studies have assessed fuel treatment effectiveness during historic fires, and in many cases found the treatment less effective than desired, particularly during extreme or record conditions. In 2007, southern California experienced one of the most severe fire seasons to-date due to record low fuel moistures early in the fire season (a key driver of the two-month long Zaca fire) and historic Santa Ana winds late in the season (resulting in several large late October fires). Climate change projections for the region suggest that these extreme conditions will be observed with increasingly greater frequency over the next half century. Southern California has one of the largest Wildland Urban Interface (WUI) extents in the country, and the extent of WUI is projected to increase significantly over the next 50 years. Fuels treatments are particularly important in mitigating wildland fire risk in WUI areas when extreme fire conditions occur. However, fuels treatments are traditionally designed to withstand historic fire weather conditions (i.e., from FireFamilyPlus), not future conditions, which makes their effectiveness less likely in the future. In order to address uncertainties in the effectiveness of fuel treatments under a changing climate, we undertook an analysis of six fuel treatments across three southern California national forests. Specifically, we 1) worked with USFS fire managers on the Los Padres, Angeles and San Bernardino National Forests to identify six critical landscape fuel treatments of concern, 2) developed downscaled projections of future climate and fire weather scenarios for 50 Remote Automated Weather Stations (RAWS) in southern California, 3) analyzed historical fire data from the region to identify an appropriate climatological testing window coincident with seasonality of fires that fuel treatments are meant to modify the behavior of, 4) tested the effectiveness of the six fuel treatments under future (mid-21st century) extreme fire weather as delineated from climate projections, and 5) developed guidelines and tools for incorporating future climate and fire weather scenarios into fuels treatment development. Additionally, due to the coincidence of the 2009 Station Fire burning into one of our six fuel treatment sites on the Angeles National Forest, we conducted an additional case study assessment of the Charlton- Chilao fuel treatment to assess its effectiveness during the Station Fire.