Over the last 20 years, both the area burned by wildfires and the number of large fires (10,000 acres or more) have increased markedly across the state. This is largely influenced by changes in fuel conditions and the effects of climate change.

Wildfires are a natural part of California's landscape. Historically, much of the state’s forests had been adapted to periodic burning. However, this natural pattern has been disrupted by changes in land use, fire management practices, and the impact of climate change. Recent fires have led to tragic losses among some of the state’s most iconic species: coast redwoods, giant sequoias, and Joshua trees. An increase in the number and severity of large wildfires throughout the western United States has been linked to hotter and drier conditions. Some experts are warning that the region has entered an era of "mega-fires." For more information, download the Wildfires chapter.

This graph shows the number of acres (in millions) burned by wildfires in California each year.

This graph shows the number of large fires (10,000 acres or more) each year, with the red line indicating the 10-year moving average. 

• The number of large fires (10,000 acres or more) has similarly increased in the past two decades. All but two of the 20 largest wildfires between 1950 and 2021 occurred since 2000; ten of these burned in 2020 and 2021.

• Wildfires threaten public health and safety, property, infrastructure, and ecosystems. Wildfire smoke contains hazardous constituents that can severely impact air quality and human health, both locally and downwind.
• Wildfires lead to, and often accelerate, changes in the state’s forests and alter wildlife habitat. For example, after a wildfire, shrubs, grasses or hardwood trees regrow and replace conifers. The loss of forests means a loss of carbon storage capacity.
• Burn areas become vulnerable to runoff and erosion. The deposition of ash, sediment, debris, heavy metals from soils, and chemical contaminants into streams and rivers threatens aquatic organisms and drinking water sources.

• California’s unprecedented drought and drought-related tree deaths increased the risk for extreme, high severity wildfires that spread rapidly. By late autumn, very dry vegetation conditions now overlap with seasonal fire-promoting winds.
• More than a century of fire suppression has led to the accumulation of fuels in California’s forests. Before Euro-American settlement, large areas of land were burned annually, ignited naturally by lightning and intentionally by Native Americans to manage the landscape.
• Land use and population changes affect ignition sources and fuel availability. For example, new housing in or near wildland vegetation has led to increased fire losses at the wildland-urban interface. The expansion of the electrical distribution system, much of it vulnerable to strong winds, increases risk of wildfires.

In 2020, 4.2 million acres burned in California, more than double the area burned in any previous year. Ten of the 20 largest wildfires since 1950 burned in 2020 and 2021, including the August Complex fire, the state’s first "gigafire,” having burned more than one million acres (left). The August Complex destroyed habitat for deer and other wildlife in the Mendocino, Six Rivers, and Shasta-Trinity National Forests (right).

Credit: USFS

• California Department of Forestry and Fire Prevention, Fire and Resource Assessment Program and Statistics