Science Says: People stoking brew that makes California burn

If you want to build a fire, you need three things: Ignition, fuel and oxygen. But wildfire in California is a much more complex people-stoked witch’s brew.

The state burns regularly because of fierce autumn winds, invasive grasses that act as kindling, fire-happy native shrubs and trees, frequent drought punctuated by spurts of downpours, a century of fire suppression, people moving closer to the wild, homes that burn easily, people starting fires accidentally or on purpose — and most of all climate change.

“California has a really flammable ecosystem,” said University of Colorado fire scientist Jennifer Balch. “People are living in flammable places, providing ignition, starting the wildfires against a backdrop of a warming climate that is making wildfires worse.”

Trying to manage California’s wildfires is like trying to hold back a tidal wave, said Columbia University fire scientist A. Park Williams: “Big fires are kind of inevitable in California.”

And it’s getting worse, fast. Area burned by wildfire in California increased more than fivefold since 1972, from a five-year average of 236 square miles (611 square kilometers) a year to 1,394 square miles (3,610 square kilometers) a year according to a 2019 study by Williams, Balch and others.

Dozens of studies in recent years have linked bigger wildfires in America to global warming, especially because it dries plants and makes them more flammable.

“ Fuel moisture drives the fire business," said University of Alberta fire scientist Mike Flannigan. "Fuel moisture is being influenced by climate change.”

In California, a Mediterranean climate sets up ideal conditions for fire then is worsened by climate change, said University of California, Merced, fire scientist LeRoy Westerling, who has had...