Researchers: Calif. wildfire season has become longer, reaches peak earlier

Environmental engineers said that higher temperatures, less air moisture and higher frequency of human-caused fires have contributed to the change


By Laura French

IRVINE, Calif. — A recent study by environmental engineers found that California's wildfire season has lengthened over the past 20 years, and now reaches its peak earlier in the year.

The researchers from the Department of Civil & Environmental Engineering at the University of California, Irvine (UCI) analyzed wildfire statistics from the California Department of Forestry and Fire Protection and compared the 2000-2019 statistics to data from 1920-1999, according to a news release.

The study, published Thursday in the journal Nature Scientific Reports, found that the state's fire seasons have lasted longer in recent years than in past years, and the yearly peak has shifted from August to July over the course of the last two decades. 

Researchers also found substantial spatial growth in fire risk throughout the state, leading to more areas being designated as fire hot spots during the 21st century. Also significant were an increase in "extreme" wildfires that burned more than 10,000 acres, and an increase in human-caused fires, such as fires started by disrupted power lines, construction, campfires or fireworks, according to the researchers. 

"CALFIRE data show that each new year of the 21st century has been a record breaker in terms of wildfire damage in California," study co-author Tirtha Banerjee, an assistant professor of civil and environmental engineering at UCI, said in a statement. "We also have seen that about 80 percent of the total number of the state's wildfires over the past few decades have been small, measuring less than 500 acres. But when fires get large, their deadliness greatly increases." 

In addition to more human-caused fires, higher temperatures, greater vapor pressure deficit (i.e. lack of air moisture) and more drought have contributed to the changes in wildfires seasons over the last few decades, researchers said. Banerjee said he hopes the information provided by the study will help government agencies and public policy officials better understand how to manage these risks. 

"The concurrence of human-caused climate change, which is drying out our forests and grasslands and creating longer stretches of hot weather, and a steady influx of people into remote areas is creating conditions for the perfect fire storm," Banerjee stated. "But there is some good news in all of this; human-caused fire risk can be mitigated by better fire management practices by humans." 

University of California, Irvine (UCI) civil and environmental engineers analyzed 100 years of state fire data, finding a significant growth in fire risk hotspots over the last two decades.
University of California, Irvine (UCI) civil and environmental engineers analyzed 100 years of state fire data, finding a significant growth in fire risk hotspots over the last two decades. (Photo/Shu Li, University of California, Irvine)

 

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