Some 102 million trees have died in California since 2010, and that number will likely grow. Dead trees in a forest are natural, but the extraordinary numbers we see in parts of the Sierra Nevada threaten many benefits of our forests. Some places that had 20 trees per acre a century ago now have 260 trees. Too many trees, dead or alive, produce too much fuel. Once a fire gets started, a continuous expanse of fuel makes it more likely the fire will become extreme. California’s wildfires affect the whole nation.