Dead tanoak trees near Little Sur River in 2007. One expert estimates that 1 million dead oak trees can be found in a 200,000-acre sweep of Big Sur forest. Flames can spread faster and toppling trees put firefighters in greater danger.
Firefighters battling to protect Big Sur are working in forests riddled with many thousands of flammable dead oak trees, making the savage Basin Complex fire burn hotter and and travel faster, forest experts said Sunday.
Hundreds of thousands of oak trees in the area have been killed in recent years by a disease known as sudden oak death, producing fuel that allows flames to spread more quickly through redwoods and other evergreens, they said.
Although the massive oak die-off has swept through forests lining California’s central and northern coasts, the Big Sur area is especially hard hit, said UC Davis plant pathology professor David Rizzo, an expert in the disease.
“It’s reached its apex in Big Sur,” Rizzo said Sunday. “The thing with Big Sur that’s making it so bad is that’s probably the worst place in the state for dead trees.”
He estimates that 1 million dead oak trees can be found in a 200,000-acre sweep of Big Sur forest that he has studied for the last three years in a federally funded study of sudden oak death. That number was confirmed Sunday by retired U.S. Forest Service forester John Kelly, who conducted aerial surveys of dead trees in area forests and is now advising Basin Complex fire managers.
Sudden oak death has been traced to a fungus-like organism, Phytophthora ramorum, that can attack tanoaks, coast live oaks and California black oaks. Tanoaks can grow 60 to 80 feet tall and are major components of the coast redwood and mixed evergreen forests common on the Big Sur coast. Trees can take several years to die, and there is no known cure.
“You look in some of these canyons, and you’ll see 70%, 80% of tanoaks are dead,” said Rizzo, who expressed concern about the Palo Colorado Canyon area that fire crews have been defending.
U.S. Forest Service forest ecologist Lloyd Williams said Sunday that the dead oaks were most prevalent on the fire’s western slope, representing about one-third of the 72,000-acre Basin Complex fire area.
“They’re added fuel to the fire,” said Williams, the botanist for Los Padres National Forest. “The intensity is much hotter. The fire burns hotter. It spreads faster.” Since many of the dead oaks are still standing, he said “The fire can go up the tree and burning embers can spread.”
The searing heat slows down crews.
“Because the fire is hotter, firefighters have to work farther away from the flames, making them harder to control,” said Kelly, who recently retired from the Los Padres National Forest. Adding to the hazards, standing trees can topple and put firefighters at risk. Their logs burn hot — some may smolder for the rest of the summer — and may kill redwoods by burning their root systems, Rizzo said.
The disease fares best in warm, moist weather, and the wet springs of 2005 and 2006 appear to have hastened its spread, he said, and the following dry springs may have killed off the trees.
During the last two summers, Rizzo and his colleagues set out 280 test plots in the Big Sur area forests, giving them a head start in studying the effects of fire on diseased forests.
“Even though our plots are burning up, from a research perspective, that’s something we can take advantage of,” he said. “Hopefully, we can use this as a learning experience, in a sad way.”