Changes

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. Better fire suppression led to many fires being generally small, but that may have contributed to larger fires decades later as forests continued to grow older with minimal fire damage. Later, the Bel Air 1961 fire (Figure 2) , about 16,900 acres burned, and Laguna fire in 1970 , about 175,000 acres, 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. Fires had been relatively small for most of the first half of the 20th century, and trees had by then become generally older. In fact, almost no new giant sequoia had been growing by the mid-20th century, as noted by ecologists. The With these new results, the Wilderness Act of 1964 and Leopold Report both now encouraged fires, particularly naturally occurring ones, wildfires to be left alone and to be allowed to burn. This may have initially enabled larger fires to develop during this time, as less suppression occurred. However, often fires would still be put out because they were deemed to be near built-up areas, leading to frequent fire suppressionas fires expanded outside of rural areas. The policy allowing fires to sometimes burn out by themselves, with the exception when fires were near built areas, became a common practice for fire suppression strategies for most of the rest of the 20th century. However, the policy was not evenly practiced. Additionally, forest management often did not involve removing old or dead trees, creating, in some placeplaces, a large number of potentially highly combustible trees. 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, however, fires were still relatively small.<ref>For a history of wildfires affecting California and elsewhere, see: Laney, K.N., 2017. <i>A century of wildland fire research: contributions to long-term approaches for wildland fire management: proceedings of a workshop </i>. The National Academies Press, Washington, DC.</ref>