California wildfires weren’t just scorching the state’s biggest cities last week. They also had an indirect impact on nearby regions, according to a study led by the University of California, Berkeley.
The study, published in the journal Nature Ecology & Evolution, found that air pollution levels in other California cities increased by the same amount as the wildfires. This showed that these large-scale disasters were associated with regional air pollution increases, which is potentially bad news for California.
Humans emit a number of air pollution culprits, including particulate matter that lodge in the lungs and can lead to disease. Some of the human-induced fine particulate matter that came from California wildfires, in addition to local pollution problems, came from fuels—especially wood and other material made from wood—that were used to clear brush and use for fuel.
“The wildfires in California were like a snowstorm in a desert,” said study lead author Emerie Bingham, a professor of atmospheric chemistry at the University of California, Berkeley. “They were huge, really hot, and the worst there was not any particulate matter in particular, but a whole bunch of particles.”
Bingham and her colleagues used weather conditions to study pollution levels in the air in local California cities around the time of the wildfire season, between Sept. 8 and Sept. 15 of this year.
They found a correlation between wildfires in forests and increased air pollution emissions in other areas. When forest fires were also accompanied by drought conditions that were affecting the state’s agricultural land, the effects were pronounced. Drought-induced air pollution also led to several wildfires in Tulare County, in the south of the state, during this time frame.
The researchers also found an indirect link between wildfires and oil and gas extraction. Both the 2012 Rim Fire and the 2003 wildfires burned over 1,000 sq km of land. In their analysis, the scientists found that the agricultural areas around these fires, especially adjacent to the Rim Fire, saw an indirect increase in pollutant emissions for three months afterward.
Bingham said the study makes it clear that fire season in California has become longer and more intense. One issue may be land-use decisions that don’t take this factor into account. “The current land-use decisions are based on historical assessment of supply and demand,” she said. “But now we can see that both supply and demand are changing, so we need to reevaluate our models.”
In its investigation of the 2013 Rim Fire, Bingham and her colleagues looked at the land burned and vegetation that was burned, and calculated the emissions of produced heat from electricity-generating facilities in California. They found that the emissions from this one wildfire from that year to that day were greater than the combined emissions from seven types of power plants in California over that same time period.
“We still have a really long ways to go to make a shift from non-renewable sources of energy to clean energy,” Bingham said. “But this study does make clear that there’s plenty of reason to say that California’s robust reliance on resource scarcity, fossil fuels, could be hindering that transition.”