Before Europeans arrived in the United States, fires burned up woody biomass in forests every 10 to 20 years, preventing the accumulation of wood fuel, and fires burned the shrublands every 50 to 120 years. But during the last 100 years, the United States Forest Service (USFS) and other agencies extinguished most fires, resulting in the accumulation of wood fuel. Keeley published a paper in 2018 finding that all ignition sources of fires had declined in California except for electric power lines.
Fire and fuel increase.
