About 75% of California's 20 most destructive wildfires—measured in terms of structures burned—have occurred since 2015.Santa Ana winds in California expand fires and spread smoke over hundreds of miles, as in this October 2007 satellite image.The Rim Fire consumed more than 250,000 acres (100,000ha) of forest near Yosemite National Park, in 2013.
This is a partial and incomplete list of wildfires in the US state of California. California often has dry, windy, and hot weather from spring through late autumn, which can foment moderate to severe wildfires. Pre-1800, when the state was more forested and its ecology more resilient, 4.4–11.9 million acres (1.8–4.8 million hectares) of forest and scrubland burned annually. California’s land area totals 99.8 million acres, and since 2000, annual burned area has ranged between 90,000 acres and 4,397,809 acres, or 0.09% to 4.4% of California's total land area.
Background
The timing of "fire season" in California is variable, depending on the amount of prior winter and spring precipitation, the frequency and severity of weather such as heat waves and wind events, and moisture content in vegetation. Northern California typically sees wildfire activity between late spring and early fall, peaking in the summer with hotter and drier conditions. Occasional cold frontal passages can bring wind and lightning. The timing of fire season in Southern California is similar, peaking between late spring and fall. The severity and duration of peak activity in either part of the state is modulated in part by weather events: downslope/offshore wind events can lead to critical fire weather, while onshore flow and Pacific weather systems can bring conditions that hamper wildfire growth.
Causes
Climate change in California has lengthened the fire season and made it more extreme from the middle of the 20th century.
Since the early 2010s, wildfires in California have grown more dangerous because of the accumulation of wood fuel in forests, higher population, and aging and often poorly maintained electricity transmission and distribution lines, particularly in areas serviced by Pacific Gas and Electric. United Statestaxpayers pay about US$3 billion a year to fight wildfires, and big fires can lead to billions of dollars in property losses. At times, these wildfires are fanned or made worse by strong, dry winds, known as Diablo winds when they occur in the northern part of the state and Santa Ana winds when they occur in the south. However, from a historical perspective, it has been estimated that prior to 1850, about 4.5 million acres (17,000km2) burned yearly, in fires that lasted for months, with wildfire activity peaking roughly every 30 years, when up to 11.8 million acres (47,753km3) of land burned. The much larger wildfire seasons in the past can be attributed to the policy of Native Californians regularly setting controlled burns and allowing natural fires to run their course, which prevented devastating wildfires from overrunning the state. There are conservation issues that prevent some controlled burns necessary to lessen the damage for when a wildfire starts.
Effects
More than 350,000 people in California live in towns sited completely within zones deemed to be at very high risk of fire. In total, more than 2.7 million people live in "very high fire hazard severity zones", which also include areas at lesser risk.
On lands under CAL FIRE's jurisdictional protection (i.e. not federal or local responsibility areas), the majority of wildfire ignitions since 1980 have been caused by humans. The four most common ignition sources for wildfires on CAL FIRE-protected lands are, in order: equipment use, powerlines, arson, and lightning.
A 2023 study found that these wildfires are affecting the California ecosystem and disrupting the habitats. It found that in the 2020 and 2021 fire seasons 58% of the area affected by wildfires occurred in those two seasons since 2012. These two fires destroyed 30% of the habitat of 50 species as well as 100 species that had 10% of their habitats burn. 5-14% of the species' habitats burned at a "high severity."
Statistics
Area burned per year
Remains of houses destroyed in the Oakland firestorm of 1991Satellite image from October, 2003 including Cedar Fire, one of the largest wildfires in California history
Starting in 2001, the National Interagency Fire Center began keeping more accurate records on the total fire acreage burned in each state.
The summer 2008 wildfires were widespread and deadly, with at least 3,596 wildfires of various origins burning throughout Northern and Central California, for around four months.
In some parts of California, fires recur with some regularity. In Oakland, for example, fires of various size and ignition occurred in 1923, 1931, 1933, 1937, 1946, 1955, 1960, 1961, 1968, 1970, 1980, 1990, 1991, 1995, 2002, 2008, and 2024. Orange County, Riverside County, San Bernardino County, and Los Angeles County are other examples. Orange and San Bernardino counties share a border that runs north to south through the Chino Hills State Park, with the park's landscape ranging from large green coastal sage scrub, grassland, and woodland, to areas of brown sparsely dense vegetation made drier by droughts or hot summers. The valley's grass and barren land can become easily susceptible to dry spells and drought, therefore making it a prime spot for brush fires and conflagrations, many of which have occurred since 1914. Hills and canyons have seen brush or wildfires in 1914, the 1920s, 1930s, 1940s, 1950s, 1960s, 1970s, 1980s, 1990s, 2000s, and into today.
On occasion, lightning strikes from thunderstorms may also spark wildfires in areas that have seen past ignition. Examples of this are the 1999 Megram Fire, the 2008 California wildfires,[citation needed] as well as the LNU and SCU Lightning Complex fires (both in 2020).
↑Stephens, Scott L.; Martin, Robert E.; Clinton, Nicholas E. (November 15, 2007). "Prehistoric fire area and emissions from California's forests, woodlands, shrublands, and grasslands". Forest Ecology and Management. 251 (3): 210. doi:10.1016/j.foreco.2007.06.005. ISSN0378-1127. Archived from the original on August 12, 2018. Retrieved August 24, 2020. area burned annually in California varied from 1,814,614 to 4,838,293 ha (excluding the desert region in Southeastern California) during the prehistoric period. With the land area of California equaling 40,396,822 ha (CCDB, 2003), this results in 4.5–12.0% of the state's lands burning annually
↑Ken Pimlott; John Laird; Edmond G. Brown Jr. (September 3, 2014). "2013 Wildfire Statistics"(PDF). CAL FIRE. Archived from the original(PDF) on December 30, 2016. Retrieved December 24, 2017.
