A report by the nonpartisan Climate Central says that 11 million people in California are at risk of wildfire and that climate change is lengthening the wildfire season.
Previous reports by researchers have said wildfires in the western U.S. would become more intense, larger, and start earlier than usual as a result of climate change.
"This intense activity is indicative of a growing trend in Western wildfires linked to changes in climate," the report notes. "Spring and summer temperatures have been rising across the West, and mountain snowpack has been melting earlier. Taken together, these changes are creating more days where forests and grasslands are dried out and ready to burn."
A fire that started June 23 near Lake Isabella in Kern County, killed an elderly couple and has destroyed more than 200 homes. Last year, six people died in fast-moving California wildfires.
The Climate Central researchers analyzed 45 years of U.S. Forest Service records of large wildfires (fires more than 1,000 acres) from the western U.S. to produce their report, "Western Wildfires: A Fiery Future."
The report says the average number of large wildfires burning each year and the total area burning in the fires have both increased dramatically since the 1970s.
"California’s size, prevalence of wildlands, and large population make it one of the states most affected by wildfire," the report says.
According to the Climate Central analysis of large wildfires (more than than 1,000 acres) on U.S. Forest Service land in California:
- California has the largest population (11.3 million) living in the wildland-urban interface of any state. This is the area where development abuts and intersperses with wild lands like forests and grasslands and where homes are more at risk from wildfire than in urban areas.
- 30 percent of California’s population lives in the wildland-urban interface.
- Over the last five years, California has seen an average of 94,000 more acres burn in large wildfires on U.S. Forest Service land than was typical in the 1970s.
- Since 2010, there are now an average 3 more large wildfires in California burning each year than there were in the 1970s.
Conditions Will Worsen
"There are now three times more large wildfires burning across the West each year than in the 1970s," say researchers. "The annual area burned in these wildfires has increased six-fold. And wildfire season is now an average of 105 days longer than it was in the 1970s. During this time, the years with the hottest spring and summer temperatures were typically the years with the most large wildfires."
The report says "conditions that foster wildfires are likely to get worse in the next several decades."
"Projections based on 29 climate models suggest that the number of high wildfire potential days each year could increase by nearly 50 percent by 2050 if greenhouse gas emissions continue unabated," according to the report. "Southwestern states, including Arizona, California, New Mexico, and Utah, are expected to see the largest increases in high wildfire potential days by 2050."
The situation in some individual states is more extreme:
- The average number of large fires burning each year on Forest Service land has increased at least 10-fold in the Northern Rocky Mountain states of Wyoming, Idaho, and Montana.
- In the Pacific Northwest, there are now five times as many large fires burning in a typical year in Washington as there were in the 1970s; in Oregon there are nearly seven times as many.