Over the past five decades, California has experienced a significant escalation in the frequency and intensity of wildfires, influenced by climatic changes, land management practices, and expanding human development.
Since the 1980s, the number of large wildfires (exceeding 1,000 acres) has risen across nearly all ecoregions in California. This uptick is particularly notable in the Sierra Nevada and southern Cascades regions.
The annual area affected by wildfires has expanded markedly. In 2020, wildfires burned a record 4.2 million acres, surpassing previous highs and accounting for over 4% of California's land area.
The intensity of wildfires, measured by overstory tree mortality and soil alteration, has increased. This trend is evident in the growing extent of high-severity burns, especially in forested areas.
Rising temperatures and prolonged droughts have dried vegetation, creating more combustible conditions. The period between September 2019 and August 2021 ranked as the third-warmest on record in California, with temperatures approximately 2.9°F (1.6°C) above average.
Decades of fire suppression have led to the accumulation of dense vegetation, providing ample fuel for fires.
Many wildfires are human-induced, including those caused by equipment use, arson, and power line failures. The increasing development near wildland areas has elevated both the occurrence and effect of fires.
The state has seen a surge in "mega-fires," defined by their rapid spread and extensive damage. Between 2000 and 2020, the area burned increased from 3% to 11% of the state's land surface.
The financial burden of wildfires has escalated, with suppression costs routinely exceeding $1 billion annually. The 2020 fire season alone resulted in over $30 billion in damages.
