A National Aeronautics and Space Administration earth resources reconnaissance plane flew high over the Santa Monica and San Gabriel mountains earlier this month to gather data for fire officials worried by the widespread death of wild brush.
Los Angeles County Fire Department officials have said they are worried by the unusual dieback of brush, which they estimate has created as much as 1 million tons of highly flammable dead wood to fuel fires in the mountains this summer. The plane's instruments scanned the mountains from 60,000 feet altitude with regular, infrared and heat-emissions-sensitive film to map the extent of the dieback.
The cause of the dieback is still under investigation, but U.S. Forest Service researchers suspect the shortage of rain this year, after several rainy winters that encouraged wild brush to grow beyond its ability to survive in a dry year.
The flight was made by an ER-2 aircraft from the NASA base at Moffet Field near San Jose.
Descendant of U-2
The ER-2 is the NASA "earth resources" model of the Air Force's Lockheed TR1-A, an advanced version of the U-2 spy plane.
The dieback is worse than was feared at first, County Fire Department Capt. Scott Franklin said.
Estimates of the extent of the dead vegetation run from 100,000 to more than 200,000 acres.
Franklin said that the problem has spread to mountain neighborhoods of Los Angeles and that patches are growing larger.
Most of the previously identified dieback zones were in the San Gabriel Mountains, where Angeles National Forest is situated, and in the large open spaces of the Santa Monica Mountains west of the San Diego Freeway.
"Now it's all through the Santa Monicas" in the heavily residential area east of the freeway, he said.
Coastal areas and canyons that receive a flow of moist air from the ocean show few signs of the dieback, he said. That fits with the theory that the dieback is associated with the shortage of rain.
Some researchers also say that the heaviest loss appears to be in areas where the vegetation is most exposed to polluted air, raising the possibility that drought-weakened brush has lost a resistance to smog that protected healthier brush in wetter years.
Officials are worried about the size and speed of brush fires in the coming season, Franklin said, and are concerned that fires fed by deadwood may burn at much higher temperatures, worsening the mud slide problem when heavy rains return.
"Hotter-intensity fires do more severe soil damage," Franklin said, particularly if the surface soil is heated to a temperature greater than 600 degrees Fahrenheit.
The seeds of some vegetation live unharmed through lower-temperature fires, and some wild vegetation, including wild lilac, has even evolved so that its seeds benefit from the usual brush fires. But higher-temperature fires not only "cook all the seeds in the soil" and prevent regrowth, he said, but also change the characteristics of the top layer of soil so that it becomes more likely to wash away in a river of mud in the next downpour.
The county Fire Department is planning controlled burns--deliberately set brush fires with firefighters in position to prevent them from spreading--to eliminate fuel for wildfires and to research the effect of fires in dieback zones. They will look particularly at the fires' maximum temperatures, he said.
One such experiment, dubbed "Project Eagle," involves burning about 200 acres near Eagle Springs in Topanga Canyon State Park at the head of Santa Ynez Canyon. The area is the site of heavy dieback and is surrounded by roads and fire roads to contain the blaze.
The burn could be carried out near the end of this month if the weather is favorable, Franklin said. About 100 firefighters will take part, he said, including some city firemen, to gain experience in battling fires in dieback zones.
Other experimental burns are planned on parts of a 250-acre parcel at the northern end of Palm Drive in La Canada and for Las Llajas Canyon on Oat Mountain, north of Chatsworth. No dates were set.