A Flammable Mix Of Man And Nature

FIRE--FED BY THE treacherous Santa Ana winds, sweeping through the canyons and roaring across the tindery flatlands--has been an essential part of nature's plan for southern California for millennia. Fire stimulates, cleanses and rejuvenates: it is nature's way of starting over again. And man, crowding by the millions into the narrow coastal strip between Santa Barbara and San Diego, has blundered into a danger zone whose risks he is only beginning to understand. Those risks are seasonal, and they are made much worse by human intrusions on the landscape and the ecosystem. If you tried to design "a really horrible fire environment," says Steve Pyne, a wildfire specialist at Arizona State University, "this would be it."

As Pyne and other experts see it, the suburban sprawl of southern California is one more example of inadvertently increasing the risk of natural disaster by trying to avoid it. "It's like the Midwest with flood control," Pyne says. "in the Midwest, the system of levees has controlled the smaller floods, which no longer spill out through the bottom lands. That saves up for bigger floods, and the big floods are much more devastating."

Nature contributes most of the raw material for the fires--chaparral thickets and coastal sage scrub that, through their normal life cycle, create vast heaps of highly flammable leaves and dry wood. Eight months of the year there is no rain, and many of these native plants have waxy leaves that form a tindery mass as they dry out and fall to the ground. Then come the Santa Ana winds, with their hot, dry air from the deserts to the east. The humidity drops drastically, and virtually any spark sets off a fire.

People compound these natural risks in several ways. One is by filling in the basins and gullies and reshaping the rolling hills for housing developments: fires, once started, spread more quickly and widely when they are exposed to the wind. Wooden houses with wooden shingle roofs--the norm for California builders until very recently--dot the canyons and hillsides with flammable targets. And when Californians fight smaller fires, they increase the risk of bigger ones. For years now, local fire departments in the region have stamped out brush fires before they get too big--after all, the remaining tracts of vacant land are surrounded by valuable real estate. But fire suppression only allows more natural tinder to accumulate in the chaparral thickets, coastal sage scrub and grasslands.

Southern California is still emerging from the six-year drought that ended in 1991. Yet paradoxically, the heavy rains of 1992 have only increased the threat of fire. That's because the rain stimulated wild new growth on the region's unbuilt acreage, adding still more dry leaves and deadwood to the underbrush. Now, as the fall winds begin to blow, fire experts look nervously at dropping "fuel moisture" and rising "bum index" data and know that the question is not if fires will break out, but when and how many. "Nature, in chaparral and coastal sage-scrub regions, is a lake of gasoline," says Richard Minnich, a fire researcher at the University of California, Riverside. "And you have to ask if it's proper to have people living in lakes of gasoline." Proper or not, Californians are going to do it--and that means southern California is once again playing with fire.