By Lisa Couper, PhD student in Ecology & Evolution
Rebecca Miller, a Stanford PhD candidate in Environment and Resources, answers common questions about recent wildfire trends and prevention and protection policies.
How do the wildfire seasons of the past few years fit into a historical context?
Miller: The number of wildfires per year in California has remained fairly steady at about 8,000 wildfires annually. However, the size of the wildfires is increasing, which suggests that we are seeing more catastrophic wildfires. In 2017 and 2018 we saw 2.9 million acres in California burned (~3% of the entire state). Further, eight of the top 20 most destructive wildfires and four of the largest wildfires in California occurred in these two years.
Additional info: Wildfires greater than 1,000 acres have become five times more frequent and burn ten times more land as those in the 1970s (Westerling et al., 2014). Further, nine of the 10 biggest fires in California history have occurred since 2003 (Cal Fire).
What is causing this trend towards larger and more destructive wildfires?
Miller: Fuel accumulation on the landscape, major wind events, and human expansion into the wildland-urban interface. We’re seeing a lot of major wind storms enabling fire to spread further and faster, making it harder for firefighters to suppress these fires. We’re also expanding human development into forest or chaparral areas and putting ourselves close to areas that have historically experienced fire. In California, 95% of fires are caused by humans. As we have expanded into the wildland-urban interface, we have brought more fire ourselves.
Is California unique in the trend of increasing wildfire destruction?
Miller: We’ve seen a general trend across the western US of larger and more destructive wildfires, but the ones in California have been particularly vivid and noticeable by the general public. They’ve also hit areas that are more well known, like wineries in Santa Rosa, which makes people pay more attention to fires here.
Flames approach rolling hills of grape vines during the Kincade fire near Geyserville, California on October 24, 2019. – The fire broke out in spite of rolling blackouts by utility companies in both northern and Southern California. (Photo by Josh Edelson / AFP) (Photo by JOSH EDELSON/AFP via Getty Images)
How is climate change impacting these wildfire trends?
Miller: Climate change increases temperatures, exacerbates droughts, and reduces precipitation and snowpack. Climate change has extended the wildfire season by 78 days relative to the 1970s—almost three additional months per year when a fire could start. This doesn’t necessarily mean that a fire is going to start on all of those days, but it means that the likelihood of wildfires is increasing. Firefighters have generally stopped using the term “fire season,” and now refer to it as a “fire year” because we’re seeing fires during seasons when we haven’t traditionally seen them.
Climate change has doubled the US forest fire area since 1984.
Additional info: Human-caused climate change doubled the cumulative forest fire area since 1984 (Westerling et al., 2014). Under conservative estimates for future warming, 11 states are predicted to experience an increase of 200% or more in average burned area for 2010-2039 relative to 1961-2004 levels (Kitzberger et al.., 2017) (Vose et al., 2012).
US Wildfires have doubled in size due to climate change. 2018 US National Climate Assessment.
What wildfire protection and prevention policies are currently in place in California?
Miller: Prevention of, and protection against, wildfire are two distinct areas of focus. To prevent wildfires, we usually do fuel treatments, which is when fuels are intentionally removed from the landscape, thus decreasing the risk of wildfire. In California there has been a recent push in the legislature to increase fuel treatments, particularly through prescribed burns. But we’re not treating nearly enough acres to address the need—in California, there are 20 million acres that need fuel treatment. That’s 20% of the state. We’re talking about a pretty significant deficit that we’re up against. On the protection side, there are things that you can do around your own property such as changing your attic vents so that embers don’t fly through, adjusting your roof to be more fire resistant, or making sure that there’s not acacia or juniper (highly flammable plants) right next to your house. These precautions are required for modern homes in high-risk areas, but most homes in California weren’t built in the last decade. But perhaps more importantly: what you do as an individual may not make any difference if your neighbors don’t do the same thing. You need to have communities work together to take these actions to improve survivability. We’ve recently seen a rise in community-led efforts to protect neighborhoods, rather than solely individual homes.
Preventatively clearing vegetative ‘fuel’ within 100 feet of buildings can reduce risk of fire spreading to the structure during wildfires.
Defensible space can only help if all homes in an area maintain one. Paradise, California after the 2018 Camp fire.
How are our prevention and protection strategies changing given the recent increase in wildfire destruction?
Miller: What gets me most excited is seeing this grounds-up approach from communities that are concerned about fires. The 2017 and 2018 fires were a wake-up call for California. We saw fires happening all over the state, in Northern and Southern California, and both urban and rural areas, at the same time. It’s no longer something that anyone can ignore – it’s truly affecting everyone.
What are the biggest roadblocks to enacting wildfire policy?
Miller: People are in favor of enacting protective policies, but we want to make sure these are intelligent polices. It’s a very hot thing for legislators to propose wildfire prevention policies right now, but those policies need to be rooted in science and realistic recognition of the challenges and opportunities to implementing these. We need more research into fire social science—what people want to see change and what people are willing to do to change. Bruce Cain, my advisor, just came out with a study that found people do not want to leave their homes. They want to continue living in fire-prone areas, despite the risks. That kind of research is critical to understanding what we can do at a policy level, because enacting policies that go against what people are willing to do is probably going to be ineffective.
Are there actions that an ordinary person—say, a student at Stanford—could take to improve wildfire protection and prevention?
Miller: It’s important to be prepared. In the event of a disaster, you have to be your own hero. I would guess that most students don’t have a couple of gallons of water in their room, a battery-powered flashlight, or enough food to last three or four days, but you should have the materials to be self-sufficient, so that first responders can help the people with the greatest need immediately.
In addition, legislators are paying attention to wildfires and are interested in proposing wildfire policies. Students could certainly do some research and contact their state senators and assembly members and urge them to implement intelligent wildfire prevention and protection policies.
Additional info: Key wildfire protection proposals enacted during the 2019 legislative session involved creating a fund to pay fire victims claims, developing a defensible space ordinance, and establishing a California Wildfire Warning Center to better predict weather conditions.
Goats are a very popular method used to manage vegetation and prevent the spread of wild fires.
For other simple and creative preventative actions, see these suggestions from CalMatters. These include fire-resistant landscaping, raking yards in fire-prone neighborhoods and using goats to manage vegetation.
Rebecca Miller is a PhD student in the Emmett Interdisciplinary Program in Environment and Resources department at Stanford University. She researches how state and local policymakers use the opportunities presented by natural disasters, like wildfires, to implement strategies that effectively mitigate the impacts of future climate change-related disasters.
Lisa Couper is a member of our writing team. She is a PhD student in the Biology department at Stanford University and researches the effects of global change on vector-borne disease.
Fourth US National Climate Assessment. Volume II: Impacts, Risks, and Adaptation in the United States. 2018.
Kitzberger, T., Falk, D.A., Westerling, A.L. & Swetnam, T.W. (2017). Direct and indirect climate controls predict heterogeneous early-mid 21st century wildfire burned area across western and boreal North America. PLOS ONE, 12, e0188486.
Vose, J. M., D. L. Peterson, and T. Patel‐Weynand (Eds.) (2012), Effects of Climatic Variability and Change on Forest Ecosystems: A Comprehensive Science Synthesis for the U.S. Forest Sector, Gen. Tech. Rep. PNW‐GTR‐870, USDA Forest Service, Pacific Northwest Research Station, Portland, Oreg.
Westerling, A., Brown, T., Schoennagel, T., Swetnam, T. & Turner, M. (2014). Briefing: Climate and Wildfire in Western U.S. Forests. USDA Forest Service.