California primed for severe fire season, but just how bad is anybody’s guess
LOS ANGELES — At this point, it seems like almost a given that California will see another historic fire season.
A meager rainy season is in the rearview mirror. Snowpack is depleted. Vegetation and soils are parched.
“All the indications are that we are heading into another really bad fire year,” said Safeeq Khan, assistant cooperative extension specialist of water and watershed sciences at the University of California Division of Agriculture and Natural Resources.
But there are still some key variables that haven’t yet taken shape. Weather events, human behavior and even luck will dictate whether 2021 goes down in the record books like 2020, when California wildfires burned an area larger than the state of Connecticut.
“We like to cite the Swiss cheese model,” said Nick Nauslar, fire meteorologist at the National Interagency Fire Center in Boise, Idaho. “You have to have enough holes in the cheese line up for us to get a season like we did last year.”
Dryness typically predicts a very active summer fire season in Western U.S. forests, said Park Williams, bioclimatologist and professor at UCLA.
“But in order to have fire you need more than just drought. You also need fuel to burn,” he said. “And so in grassland areas, the fire season might not actually be so bad because there’s not a lot of whole new grass to burn.”
Counterintuitively, an extremely dry year can actually mean Southern California will see fewer fires, as flames often spread from a human source into nearby shrublands or forests, said James Randerson, professor of earth system science at UC Irvine.
“If you think of a road and a car with a muffler that’s dragging, if it’s a year with a lot of moisture, then the fine fuels and all the grasses along the roads will be connected more to that chaparral area nearby,” he said.
“It’s my sense — and it’s supported by our analysis of some of the data from Cal Fire — that there’s a lower risk for having a large number of fires when you have a drought like this, because it’s cutting into the connectivity of the fine fuels and the herbaceous fuels, all the grasses.”
But Randerson’s research with Yufang Jin of UC Davis has also indicated that once fires do start under these conditions, they tend to grow larger and escape human control more quickly.
“When there’s drought there may be fewer fires, but when they do ignite they tend to move faster, can get bigger and be more destructive,” Randerson said. “The fuel is drier so they move more rapidly out of containment.”
The number of hot days is also key, he said.