Energy & Environment

Humans are the cause of most wildfires. Climate change will make that worse

Flames consume the bark of a tree
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Climate change is exacerbating wildfire dangers across the West, creating the perfect conditions for the main culprits to start damaging fires: human beings.

People are the driving force behind the changing climate, and they are also the driving force behind most fires.

Data from the National Interagency Coordination Center indicates that the vast majority of wildfires, 88 percent on average, were ignited by human sources from 2016 to 2020.

As recently as last week, utility Pacific Gas and Electric (PG&E) said in a disclosure to the California Public Utilities Commission that it believes its equipment was connected to the ignition of the Dixie Fire, which has reached 40,500 acres as of Wednesday.

Fires are also regularly started by people going about their lives.

In one of the more unusual cases, a couple on Tuesday was charged with involuntary manslaughter after their gender reveal party ignited a 2020 wildfire in San Bernardino County, leading to the death of a firefighter.

The year before, officials from the California Department of Forestry and Fire Protection (Cal Fire) determined that the October 2019 Kincade Fire was caused by downed PG&E transmission lines. The Sonoma County fire displaced nearly 100,000 people and burned 374 homes.

A 2018 report by the California State Senate Energy Committee determined electrical power was the third-most common cause of wildfires in the state, ahead of arson, lightning and campfires.

Statistics from Cal Fire further indicate that of the 20 deadliest wildfires in state history, at least 10 were human-caused, whether through power lines, vehicles, arson or other unspecified human causes. The 2018 Camp Fire, the deadliest in the state’s history, began that November as a result of a power line malfunction. At least 10 of the most destructive fires on record in the state were also human-related.

While individual human error is often a major factor in ignition, often the root causes come back to institutional problems, whether due to inaction on climate change or issues with electrical infrastructure.

In California, the utilities’ infrastructure runs through highly flammable areas.

“There’s just no question about that because we bring electricity long distance into the urbanized areas,” said Stephanie Pincetl, a professor in residence at the UCLA Institute of the Environment and Sustainability. “So the more that that electricity goes through highly burnable areas — we’re not really maintaining the corridors well — the likelihood of fires being ignited increases.”

Pincetl added that aging infrastructure is not the sole factor in California wildfires but has accompanied other forms of institutional neglect such as the lack of sufficient controlled burns over the past century.

“And so, when you have an aging infrastructure running through forested areas that haven’t been maintained themselves, the chances of that ignition occurring is much, much higher,” she said. “And it’s not up to the utilities to really manage forest health by doing controlled burns for the forest. So it’s an infrastructure that is embedded in a larger system that itself hasn’t been very well managed.”

Human-ignited fires can be vital for conservation in the case of controlled burns, and they occurred throughout the western U.S. before European colonization, noted Sean Parks, a research ecologist with the U.S. Forest Service.

“It’s when they occur near cities or when they occur in high winds or in situations where the forests are really thick” that they become a problem, Parks said.

The reason so many recent human-caused blazes have spread out of control, he added, is “because they’re often in proximity to human infrastructure and communities and what have you.”

As human infrastructure represents more and more of the western landscape, the coexistence with fire that was once the status quo becomes more difficult, Parks added.

Fires ignited through human activity can also be easier to start and harder to extinguish based on environmental factors such as temperature and dryness of vegetation.

“When stuff is dry, it will burn more easily regardless of how it is ignited,” bioclimatologist Park Williams, an associate professor of geography at UCLA, told The Hill. “Drought conditions are generally not direct causes of ignitions, but they do greatly enhance the probability that a given ignition leads to a large wildfire.”

Although it is difficult to determine direct causation, both increased heat and more extreme weather due to climate change increase the risk from human-ignited fires.

“While it hasn’t gotten as much study, it would also appear that there’s an increase in the number of red-flag days, or the number of days affected by high-wind incidents,” according to Sabrina Drill, the natural resources adviser for University of California Cooperative Extension in Los Angeles and Ventura counties.

These conditions can be particularly dangerous in Southern California, where the majority of fires are driven by drifting embers, she added. In addition to spreading individual fires, she noted, high winds can increase the rate at which moisture in vegetation evaporates. The couple whose gender reveal ignited the San Bernardino County fire were unable to extinguish it with water bottles due to the high winds present at the site.

“That’s also why during big wind events we have a lot of these power companies actually shutting power off,” said Max Moritz, a cooperative extension wildfire specialist at the Bren School, UC Santa Barbara.

This season in particular, Moritz said, has seen a potent combination of lack of rain and heat waves. The result is both a low starting point for vegetative moisture and high evaporative demand, or the extent to which the environment works to evaporate water.

As a result, “we just got fires igniting more easily, all things considered,” he said.

“One of the things that happens with increasing temperatures due to greenhouse gases and all these other conditions is that there’s just more energy in the environment,” Drill said. “That’s why we worry more about extreme events and things like superstorms and tornadoes becoming more common. The same thing [applies] in fire conditions.”

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