Mystery Ailment : Fire Danger Up as Killer of Mountain Brush Shifts Into High Gear After Unseasonal Rains

The hills of Southern California are lush with greenery, nourished by unseasonal autumn rains, which should have been good news for firefighters and forest researchers worried by the mysterious “die-back” that has been killing brush on the mountainsides for the past three years.

Instead, it has turned into bad news. When the cavalry finally arrived, it ended up helping the enemy.

Because the die-back was blamed in part on four years of drought, the expectation was that the rain would ease the problem.

Researchers say it has made the problem even worse. The die-back, which appeared to have peaked more than a year ago, has unexpectedly gone into second gear, ravaging what remains of brushy areas depleted by the first round.

“In some areas of the Santa Monica Mountains, the die-back is approaching 50% or more” of the brush, Capt. Scott Franklin, the Los Angeles County Fire Department’s vegetation management coordinator, said last week.

“We don’t have a firm count, but a conservative estimate would be that it has already killed about 15% to 20%” of the brush in Southern California, he said.

Added Fuel for Fires

The dead, tinder-dry brush provides “tons of additional fuel per acre in a brush fire,” Capt. Ron Mathis, superintendent of a county firefighters camp in La Canada Flintridge, said as he surveyed a hillside in the nearby San Gabriel Mountains with Franklin and Philip J. Riggan, a U.S. Forest Service scientist who has been one of the leading researchers into the phenomenon.

“If these were trees instead of brush--things like redwoods that people get emotional about--the public would be going crazy,” Riggan said.

They may yet, he said, because there are some indications that the die-back is spreading to ornamental shrubs and trees in the yards of suburbanites in mountain brush areas. There is also the possibility that it could kill some of the venerable oak trees prized by conservationists, he said.

For the time being, however, attention is focused on the die-back because it has greatly increased the danger of brush fires, not because it threatens backyard pepper trees.

The Forest Service, state Department of Forestry and county fire authorities have been investigating the die-back since it was first noticed because it adds to the fire danger.

Dead brush burns more readily, as well as hotter and faster, than live brush. The swifter burning rate increases the danger that a blaze will flare into a populated area or that an eruption of flames will trap firefighters, injuring or killing them, said David R. Neff, regional resources program manager for the Department of Forestry.

Soil Hit 1,200 Degrees

Instruments placed in the path of fires in areas devastated by the die-back showed that soil temperatures reached levels as high as 1,200 degrees Fahrenheit, twice as hot as temperatures in burning areas with mostly live vegetation, Franklin said.

The higher temperatures do more damage to topsoil and chaparral seeds, worsening soil erosion and mud slide problems and making it more difficult for the burned-over area to recover.

Especially worrisome for firefighters is the loss of ceanothus , also called wild lilac, a widespread shrub that has been one of the chief victims of the die-back. Healthy wild lilac has a high moisture content and resists burning, forming a natural fire damper.

The die-back, first seen in the San Gabriel Mountains in 1984 and then in the Santa Monicas in 1985, is evident throughout Southern California, Neff said.

“Now we find it in Santa Barbara County--up around Lake Casitas is the northernmost reach--and south to Temecula in San Diego County and eastward into Riverside County,” Neff said.

In June, 1985, at the request of die-back researchers, the National Aeronautics and Space Administration flew an ER-2 reconnaissance plane--a civilian version of the U-2 spy aircraft--over Southern California at 60,000 feet, photographing the area with regular, infrared and heat-sensitive film in an attempt to map the extent of the blight.

Researchers say they still do not understand the origin of the die-back. It does not seem to have a single cause, but is the result of several interacting factors, perhaps including some that are not yet known, they say.

One of the factors appears to be a fungus-- botryosphaeria ribis --which was identified by state researchers in 1986 and has been found in wild lilac bushes in die-back areas.

Rain Theory

But the fungus alone does not seem to cause the die-back, Riggan said. It appears to be common throughout the chaparral area, but otherwise healthy plants usually resist it, he said. One theory is that the heavy rains of 1982 and even heavier storms of 1983--the year the El Nino condition in the Pacific Ocean sent a series of destructive downpours through Southern California--encouraged the chaparral to grow larger, or faster, than normal.

“They just grew like crazy after those storms in ‘83,” Franklin said.

But the overextended shrubs had trouble surviving in the drought that began in 1984 and has continued since then because their excessively large root systems could not find enough moisture in the soil.

The weakened shrubs were then finished off by the fungus, Riggan and others have theorized.

Riggan also suspects that air pollution is involved since shrubs in areas with high pollution levels are more susceptible to the blight, but he said he does not have enough data to prove the point.

‘Spreading Again’

If the lack of water was the trigger for the epidemic, however, the recent rains should have fortified the chaparral, easing the problem.

“But when we checked, we found it was spreading again, faster than ever before, which seems to fly in the face of the drought idea,” Franklin said.

It seems clear by now that the rain has been causing the die-back to spread, Riggan and Franklin agreed. “The die-back is appearing in large areas that resisted it before,” he said.

Why, they don’t know.

Franklin speculated that the rainfall was warmer than later winter rains, which may cause the fungus to spread.

Vexing Question

One of the most vexing questions for researchers is whether the blight is unprecedented or if it has happened before.

Neff said state researchers and consultants with more than 30 years of experience, “people who have spent all their lives observing the chaparral, have simply never seen anything like it.”

Riggan says he has found nothing like it in scientific literature, “but there are clues that maybe this has happened before, but the researchers didn’t recognize it.

“Years ago,” he said, “they used to believe that chaparral just had a short life span, which we know now isn’t necessarily true.”

Researchers have no idea what to do to combat the blight, he said.

“This is a whole natural ecosystem. Unlike the forests up north, which have been cut over by loggers, sometimes many times, this system is the way nature made it.

“And it’s just vanishing before our eyes.”