Dry forests fuel wildfire risk
Die-off slows, but toll of 147 million trees since 2010 alarms state
years after California’s historic drought came to an end, the sweeping die-off of the state’s forests has slowed, yet vast tracts of dry, browning trees continue to amplify the threat of wildfire, federal officials reported Monday.
About 18.6 million trees died in 2018, mainly the result of dehydration and beetle infestation, according to new estimates from the U.S. Forest Service. That pushes the total number of dead since 2010, shortly before the five-year drought began, to 147 million. It’s a toll not seen in modern times.
With once-green mountainsides still basking in startling hues of rust and apricot, particularly in the Southern and Central Sierra, federal officials warned that weakened trees are apt to fall atop roads, power lines and homes while woodlands remain in such poor shape that they’re ripe for burning.
Even President Trump has taken shots at the grim condition of California’s wildlands lately, calling for more active forest management. Federal officials are working with state and local governments to try to restore the health of the forests, but they’re up against a die-off that’s become increasingly entrenched and only hasTwo
tened by a warming climate.
“If this continues, we’re going to have massive problems, particularly related to wildfire,” said Randy Moore, regional forester for the Pacific Southwest Region of the Forest Service. “It makes it complicated to do all the suppression we need to do to protect communities.”
Over the past two years, California has already experienced some of its most destructive wildfires. The November Camp Fire in Butte County killed 86 people and destroyed nearly 14,000 homes.
In addition to the risk of fire and falling trees, federal officials cautioned Monday that the sprawling stands of dead trees threaten to undermine such critical forest functions as providing clean water and absorbing heat-trapping carbon dioxide.
Fortunately, Moore said, the rate of tree mortality decreased last year. The number of dead trees was a third less than in 2017 and about two-thirds less than in 2016. That year, at the peak of the drought, 62 million trees perished.
Deciphering the exact cause of death is difficult, officials say, as trees can die from dehydration or pest infestation, or a combination of both. Native bark beetles take advantage of the tree’s drought-depleted defenses, often delivering the fatal blow.
While it’s unclear if mortality rates will continue to decline, most forest experts say a third year of improvement could signal that a recovery is under way.
“It is encouraging that the rate of mortality slowed,” Thom Porter, director of the California Department of Forestry and Fire Protection, or Cal Fire, said in a statement Monday. “However, 18 million trees are an indication that the forests of California are still under significant stress.”
California’s dead trees are mostly concentrated in the Sierra, south of Lake Tahoe, at low- to mid-level elevations. Ponderosa Pine, as well as cedar and oak trees, have been hardest hit. The epidemic, though, has spread to higher elevations, where sugar pine and fir are prevalent, as well as to the northern half of the state, including coastal areas.
Four years ago, the state convened a Tree Mortality Task Force, consisting of local, state and federal land management agencies, along with power companies and timber harvesters. The group has since helped coordinate the removal of more than 1.5 million dead trees.
While the program has made only a dent in the problem, its focus has been clearing the most hazardous of the lifeless trunks, like those imperiling communities in densely forested areas and along highways. State and federal officials have also opted to close some Sierra roads and recreational sites out of concern of tumbling trees.
Tree-removal efforts have recently been joined by broader initiatives by Cal Fire and the U.S. Forest Service to shore up the forest health. In the wake of recent wildfires, both agencies have pledged to restore native vegetation, thin overgrown woodlands and rejuvenate the landscape with controlled fire.
Gov. Gavin Newsom last month proposed an additional $305 million for such forest management activities in the state budget.
“I’m really optimistic that we’re going to begin to make a difference,” Moore said.
While the recent push by state and federal agencies has generally been met with applause, the past management of California’s wildlands has actually exacerbated the tree die-off, many forestry experts say.
A longtime policy of aggressively putting out fires that can be beneficial, because they clean and strengthen woodlands, has created a buildup of trees that’s left forests more crowded and vulnerable.
Chad Hanson, a research ecologist with the John Muir Project, said the tree die-off is simply nature restoring itself.
“We don’t want too many areas of live forest and we don’t want too many areas of dead forest,” said Hanson, who has written extensively about the need for new trees and plants to blossom from the loss. “We want a balance in the forest.”
Hanson estimates that about 9 percent of the Sierra is in a recovery phase, which he maintains is lower than the amount of forest that would be in this state naturally.
Some scientific studies also have shown that these recovering areas, with lots of dead trees, are at no more fire risk than areas with few dead trees. These studies note that lifeless trees have fewer needles and less foliage to burn.
Moore said this wasn’t his experience, however. But either way, he agreed that the forests are not in equilibrium and would be much better off in their natural state.
“We have to increase the pace and scale of restoration,” he said.