Fuels, fire suppression, and the California conundrum Eric Knapp U.S. Forest Service, Pacific Southwest Research Station Redding, CA Bald and Eiler Fires - 2014; Photo: T. Erdody How did we get here? 2018: Most destructive wildfire (Camp Fire) Largest wildfire (Mendocino Complex) Most acres burned in modern CA history 2017: 2nd most destructive wildfire (Tubbs Fire) 2nd largest wildfire (Thomas Fire) Mediterranean climate = fire climate Redding, CA (Elev. 500 ft) 8 100 7 6 80 F) o 5 Wildfire season 4 60 3 Precipitation (in) 2 40 Ave Max.Temp. ( 1 0 20 1 2 3 4 5 6 7 8 9 10 11 12 Precipitation Month Temperature • Very productive – grows fuel • Fuel critically dry every summer • Hot/dry = slow decomposition Fire activity through time Shasta-Trinity National Forest (W of Trinity Lake) 1750 1850 1897 Fire return interval 3 years 12 years No fire since 1897 Fuel limited fire regime | Ignition limited fire regime • Fire was historically a combination of indigenous burning and lightning ignitions • Aided travel, hunting, and improved the qualities of culturally important plants • Many early Euro-American settlers initially continued to burn • Forage for grazing animals • Lessened the danger from summer wildfires • Foresters advocated for Halls Flat, A. Wieslander, 1925 suppressing fire • “The virgin forest is certainly less than half stocked, chiefly as one result of centuries of repeated fires” – Show and Kotok 1925 • Believed keeping fire out would be cheaper than treating fuels with fire Burney area, A. Wieslander, 1925 Change in structural variability (trees > 4 in.) 1929 2008 Methods of Cutting Study – Stanislaus National Forest Lack of fire also changed non-forests A. Wieslander, 1932. Redding area [shows brush converted to grassland by burning] Area burned by year - California Acres burned historically, pre-1800 (4.5-12 million) - Stephens et al. (2007) 5000000 4000000 3000000 Prescribed fire in 9 year old fuels Acres burned Acres 2000000 1000000 P < 0.001 Rim Fire 0 1980 1990 2000 2010 2020 Years Change in fire size distribution over time with fire suppression (Forest Service lands, northern and central CA) Fire size distribution 2000000 1911 to 1924 1500000 2002 to 2015 1000000 500000 Total acres burned 0 <10 10-100 100-300 >30000 300-1000 1000-5000 5000-30000 Fire size category (acres) • Fire suppression has not removed fire from our ecosystems. • It has mainly changed the frequency, intensity, and size. Collins BM, JD Miller, EE Knapp, DB Sapsis. 2019. A quantitative comparison of forest fires in central and northern California under early (1911-1924) and contemporary (2002-2015) fire suppression. International J. Wildland Fire 28:138-148. Climate and fire Western Regional Climate Center - http://wrcc.dri.edu/climatedata/climsum/ • Reduced snowpack, longer fire seasons • Greater fuel aridity • Increased stress on vegetation: mortality = more dead fuel Fire behavior controlled by multiple factors • Relative influence varies with fires, but fuels the overriding factor • Climatic warming: increased odds of factors conducive to extreme fire behavior co-occurring • Weather plays an outsized role today in part because of fire suppression • More fuels for weather to act on • Burned acres increasingly from fires burning under the most extreme weather conditions • Fuel is what we can change Summary/ thoughts on greater resiliency to fire • Excess fuel loading today due not just to fire suppression. We also largely stopped using fire for our benefit. • How to change the current dynamic? • Align decision making with the current and future fire reality • Living with Fire: fire is inevitable - manage forests, design infrastructure, and build homes accordingly • Suppress wildfire when necessary but replace with other investments in fuel reduction • Better fuel management will not eliminate all extreme fire behavior. Home and infrastructure hardening is key too..