Wildfires in northern and central California increased fivefold between 1971 and 2021, according to a new study published by the Proceedings of the National Academy of Sciences (PNAS). The scientists behind the study found that those fires were mostly caused by anthropogenic climate change, the kind accelerated by human actions like burning fossil fuels and clear-cutting land.
As part of their research, the scientists did a statistical analysis of the summer months during those four decades, which helped them understand how the California landscape might have looked without human-caused greenhouse gas emissions. They discovered that the wildfire burn area grew 172% more than it would have in the absence of such emissions.
Compounding the problem, poor forest management leaves brush and dead wood that fuel fires, according to the researchers. Drier and hotter conditions make this organic matter ripe for ignition. Meanwhile, clear-cut areas allow fires to spread faster and grow out of control.
Five of California’s 10 biggest fires were in 2020
The past two decades have seen the 10 largest wildfires in California’s history. Half of those occurred in 2020 alone, including the August Complex, North Complex, LNU and SNU Lightning Complex, and Creek fires. Eight of the top 10 biggest wildfires in the state took place from 2017 onward.
The August Complex blaze of August 2020 was California’s largest, burning more than a million acres (roughly 400,000 hectares). The Dixie fire of July 2021 consumed some 900,000 acres. In total, the state’s 10 biggest wildfires have burned around 4.8 million acres.
In their study, the scientists estimate that the area burned during an average summer in northern and central California could surge up to 50% by 2050 if current levels of drought and extreme heat continue. They hope their research will prompt immediate action to reduce CO2 emissions, helping reverse the higher temperatures driving these wildfires.