What’s Behind California’s Surge of Large Fires?
If it seems like enormous wildfires have been constantly raging in California in recent summers, it’s because they have. Eight of the state’s ten largest fires on record—and twelve of the top twenty—have happened within the past five years, according to the California Department of Forestry and Fire Protection (Cal Fire). Together, those twelve fires have burned about 4 percent of California’s total area—a Connecticut-sized amount of land.
Two recent incidents—the Dixie fire (2021, above) and the August fire complex (2020)—stand out for their size. Each of these burned nearly 1 million acres—an area larger than Rhode Island—as they raged for months in forests in Northern California. Several other large fires, as well as many smaller ones in densely populated areas, have proven catastrophic in terms of structures destroyed and lives lost. Thirteen of California’s twenty most destructive wildfires have occurred in the past five years; they collectively destroyed 40,000 homes, businesses, and pieces of infrastructure.
The total area burned by fires each year and the average size of fires is up as well, according to Keith Weber, a remote sensing ecologist at Idaho State University and the principal investigator of the Historic Fires Database, a project of NASA’s Earth Science Applied Sciences program. The database shows that about 3 percent of the state’s land surfaces burned between 1970-1980; from 2010-2020 it was 11 percent. The shift toward larger fires is clear in the decadal maps (above) of fire perimeter data from the National Interagency Fire Center.
“The numbers are really worrisome, but they are not at all surprising to fire scientists,” said Jon Keeley, a U.S. Geological Survey scientist based in Sequoia National Park. He is among several experts who say a confluence of factors has driven the surge of large, destructive fires in California: unusual drought and heat exacerbated by climate change, overgrown forests caused by decades of fire suppression, and rapid population growth along the edges of forests.