In today's SB Sun:
Smog increases fire threat
Pollution stunts tree roots, alters soil
Mountain residents are all too familiar with the multiple-whammy that turned the San Bernardino National Forest into a tinder box earlier this decade.
One of those factors was drought, and with a bone-dry winter just past, another scary fire season is effectively here already.
On top of the well-documented villains, it turns out there's something else that drove the forest into its dangerous state - smog.
Air pollution scrambled the ways trees develop and how they react to drought, researchers have found.
And in one of those scientific ironies, smog killed some trees while at the same time dumping tons of nitrogen into the soil that nourished the tree overpopulation.
The pollutants retarded root development, like a short straw in a half empty glass.
The smaller root systems also force carbohydrates and amino acids to be stored in the lower trunks, making them even more attractive to bark beetles.
"It's like McDonald's," said Nancy Grulke, a plant physiologist at the U.S. Forest Service Fire Lab in Riverside who studies the effects of air pollution on the forest.
The situation had its start more than 100 years ago.
Miners, loggers and settlers cut down trees for cabins, mine shafts and timber in the San Bernardino Mountains.
When a punishing drought hit in 1899, water had to be hauled up the mountain from the valley.
Needing a reliable water supply, dams were built, creating Lake Arrowhead, Lake Gregory and Big Bear Lake.
Those glistening jewels drew tourists to the beautiful scenery and cooler temperatures beginning in the 1920s and 1930s. No longer were gold and timber the main attraction.
"With the recreational uses, they started building hotels and cabins, and didn't want to cut anything," Grulke said.
As the population of preservation-minded people increased in the mountains, so did the population of trees, competing for water and nutrients from the soil.
The logging that had reduced the number of trees ended, and fires that would naturally thin the forest were quickly extinguished, forcing the trees against each other ever more tightly.
A century later, another fierce drought hit, setting the table for millions of bark beetles that would decimate the forest and create one of the greatest fire dangers in the west.
Beginning in 2001 and 2002, swaths of dying orange-needled pine trees sprawled across the forest as the parched trees became easy prey for the small voracious bugs.
The whine of chainsaws became the unofficial songbirds of the mountain communities as public agencies and mountain residents began cutting the dead trees as fast as they could.
Everyone prepared for the worst.
The nightmare erupted into reality in October 2003 when the Grand Prix and Old fires, driven by Santa Ana winds, roared through the foothills and then raced back up the mountainside into the beetle- killed trees.
When the smoke cleared, nearly 1,000 homes had been destroyed and 91,000 acres torched.
Could we be ripe for another attack by bark beetles, which are a natural phenomenon much like fire, helping to correct an out-of-balance forest?
Rainfall totals this season are a fraction of normal, and similar to the dry season of 2001-2002.
It's possible, but the situation is much better now than it was in 2002 and 2003, Grulke and other experts said.
The fire plus more than 1 million trees cut down in recent years have the forest headed toward a healthier condition.
Research on drought and bark beetles indicates there were no infestations in the first half of the 20th century even during droughts. The first reported case of beetle infestation on the heels of a drought came in 1949, Grulke said.
That was a few decades after the logging stopped and about the time the forest would have been getting unnaturally dense.
"If we can keep the forest thin, we can reduce tree mortality," she said.
Richard Minnich, a professor at UC Riverside, agrees. He's studied forest health for years and worked with Grulke on her research.
"I don't see a big die-off," he said. "The trees aren't nearly as stressed as they were in 2002."
But neither did he want to downplay the risk. Though thousands of acres have been thinned, a daunting amount of work remains before the entire forest can be called safe.
"There's still a gigantic fire danger in the mountains," he said.
