Patty Guerra

Wildfires are growing more frequent and severe across the western United States, and California's Sierra Nevada is ground zero. Decades of fire suppression have left these forests overstocked and vulnerable to catastrophic fires, drought and pest outbreaks.

Beyond destroying homes and infrastructure, high-severity wildfires release massive amounts of carbon, degrade water quality, erode soils, reduce timber supply and fill the air with hazardous smoke that threatens public health.

Lightning from thunderstorms rolling through Central California on Sept. 2 ignited numerous wildfires, including several large fires in the Sierra Nevada foothills that had burned more than 19 square miles by Wednesday morning. The California Governor’s Office of Emergency Services recorded more than 9,000 lightning strikes in a single day.

Lightning is a major source of wildfire ignition in the western United States every summer.

Pictures accompanying Professor John Abatzoglou's presentation on the 2025 fire season were blurry. That was intentional, he said, because so much about wildfire is unpredictable.

"There's a lot that we know, and a lot we don't know," he said.

Recently, more than 150 students at 10 high schools in Los Angeles, New York City and Washington, D.C. completed Climate Justice, a UC Merced course , through a unique partnership between the University of California and the National Education Equity Lab.