What is the history of wildfires in California?

Wildfires are not only natural but they help keep forests healthy and help renewed growth. However, wildfires, appear to have become more intense in recent history, particularly in places such as California, where the weather is often dry in many parts of the state. Looking at the history of wildfires, reasons as to why they have become more destructive become clear.

Early Record of California Wildfires

The archaeological and ecological record in California reveal a long history of wildfires in the state of California. In a study looking at pre-1800 wildfires, almost 1.8 million hectares were estimated to burn annually in California. This is about the level that has burned as of early October 2020. Scientists estimate that the summer and autumn seasons were often filled with smokey skies of burning forests.

One of the first major recorded wildfires occurred in 1889; sometimes called the Great Fire of 1889 or the Santiago Canyon Fire. The fire mainly occurred in what are today's Orange, Riverside, and San Diego counties. Until 2018, this may have been the largest single wildfire event in California's recorded history, with over 300,000 acres burned. It started in September 24 and continued to September 30th. The fire was preceded by a very dry season, with only 0.4 inches of rain during the rainy season and strong Santa Ana winds were recorded that year. Other fires occurred that year, including in San Diego, but were far larger. The 1871 Peshtigo fire, which occurred in Wisconsin, influenced policy regarding wildfires in the late 19th century. Fire suppression strategies already began to be evident in places such as Yosemiti, General Grant, and Sequoia national parks. The Peshtigo fire covered 1.2 million acres and became the most deadly wildfire in US history, with 1500-2500 people killed in relatively rural areas of northeast Wisconsin. The 1889 Santiago Canyon Fire also led to more intense fire suppression strategies to avoid loss of life and property. This meant that as soon as fires started, policy was to put out the fires as quickly as possible.

Twentieth Century Wildfires

In the early 20th century, recorded fires were relatively small in scale but became destructive as the infrastructure and towns in California became built-up. The Berkley Fire of 1923 and Griffith Park Fire in 1933 are two examples of fires that were only about 10s of acres, although in the case of the Griffith Park Fire about 29 people died. This period saw that policy around fire suppression became more established, with the US Forest Service stating that wildfires were to be put out by 10 AM after the day a fire began. Later, the Bel Air 1961 fire and Laguna fire in 1970 were larger, indicating that fires began to get larger by the mid-20th century and later. By this time, increasingly scientists realized forest with large trees were not growing new trees as there were few large fires. In fact, almost no new giant sequoia had been growing by the mid-20th century. The Wilderness Act of 1964 and Leopold Report both encouraged fires, particularly naturally occurring ones, to be allowed to burn. This may have initially enabled larger fires to develop during this time. The policy allowing fires to sometimes burn out by themselves, with the exception when fires were near built areas, became the common practice for fire suppression strategies for most of the rest of the 20th century. Perhaps the most devastating fires over the next few decades were the Panorama Fire in 1980, which burned 28,800 acres and killed 4 people, and Oakland firestorm in 1991, which burned about 1500 acres and killed 25 people. Once again, fires threatening built areas made these fires devastating rather than the fact they were very large fires. By historical standards, fires were still relatively small.

Recent Wildfires

What has changed is that since 2000, the scale of wildfires has now become far larger. In 2000, about 300,000 acres burned in total in the state of California. By 2018, the total was almost 2 million acres. The most likely factors causing this trend is the fact the fire seasons is now historically longer than it was over the 20th century, when fires were relatively small. Additionally, many trees have also died over multi-year droughts, causing a larger fire hazard as dead trees are not cleared or left standing in forests.