Another violation of my self-imposed blog vacation to link to an LA Times article on chaparral. The story profiles Rick Halsey, a former high school science teacher, who is the founder of the California Chaparral Institute, a nonprofit environmental group. (What a nice switch of jobs. According to the article his wife makes the bulk of the money.)
The story frames a debate between Halsey and governmental forces about the merits of proscribed burns in the California back country. There's a lot of fear among San Diegans about fire, and one proposed solution is to burn the back country. Many people believe that fire is an essential renewing event in the California chaparral. This widespread opinion dates to a 1983 article in Science which is now believed not to be correct in some essential ways. Most importantly, the true role of fire is as a once per century event, rather than a once per 30 years event.
How often fire burned through Southern California before humans arrived is the subject of much scientific and public policy debate.
The only nonhuman source of fire is lightning.
But does lightning spark many brush fires in Malibu? And does lightning occur during blue-sky Santa Ana wind conditions?
The answers are no.
Fire prevention policy has centered on a much-disputed study published in 1983 in Science magazine, which suggested that modern fire suppression had caused too much fuel build-up. In the article, UC Riverside professor Richard Minnich concluded that, historically, fires were small and burned frequently -- leaving a patchwork mosaic of fuels of varying ages that prevented fires from scorching vast acreage. He believed chaparral less than 20 years old didn't have enough dead material to burn.
This encouraged land managers to conduct prescribed burns in the backcountry to get rid of the old, most volatile fuel.
But many scientists have since rejected the findings.
Hugh Safford, ecologist for the U.S. Forest Service Pacific Southwest region, said wind-driven fires roar through young chaparral and old chaparral alike. While older vegetation has more dead wood to intensify the flames, it matters only when the vegetation is adjacent to homes.
"Under Santa Ana wind conditions, it doesn't matter how old it is," he said. "Re-burns in 3-year-old chaparral are common, and some of these fires even burned through 1-year-old chaparral."
Jon Keeley, a fire ecologist for the U.S. Geological Survey, suspects the pre-human wildfires were huge -- but happened only once a century in any given area. The likely mechanism: Lightning during a monsoonal August storm started a fire in the high mountains that smoldered for months; the Santa Anas picked it up in October or November and drove it all the way to the coast.
Because native Americans didn't arrive in California until about 10,000 years ago, and evolution takes much more time than 10 millenniums to do anything worthwhile, this model is what the plants adapted to.
Strangely, the Times didn't provide a link to the Chaparral Institute.