It is the forgotten killer when compared to our increasingly frequent climate calamities, but the virulent pathogen known as sudden oak death remains active and is spreading death so fast it could destroy California’s coastal forest ecosystem, UC Berkeley scientists reported Thursday.
The deadly microbe has now established itself throughout the Bay Area and has spread along the coast from Monterey to Humboldt County, according to a study of 16,227 trees in 16 counties in Northern California.
Millions of coast live oak and tan oak trees have withered and died over the past quarter century, leaving acres of kindling for wildfires, but the outbreak this year was one of the worst. Oak trees have historically been abundant in California and southwestern Oregon, with hundreds of millions of them stretching all the way to Baja California.
The rate of trees infected almost doubled in 2019 — from 3.5% to 5.9% — and was 10 times higher in some places compared with the 2018 survey, said Matteo Garbelotto, the director of the UC Berkeley Forest Pathology and Mycology Laboratory, which tested leaf samples taken by 422 volunteers.
A dry winter curtailed the presence of a deadly forest pathogen this year in Sonoma County and 13 other Northern and Central California counties, but experts still expect the oak-killing disease to spread and warned landowners to be vigilant.
Since the mid-1990s, sudden oak death has killed up to 50 million trees from Big Sur to southwest Oregon and is entrenched in the woodlands, spreading rapidly after wet winters and slower during dry years.
“It’s constant, it’s emerging,” said Richard Cobb, an assistant professor of forest health at Cal Poly San Luis Obispo. “It’s probably going to get a lot worse.”
Cobb said Monday he’s about to publish his estimate of tree mortality, 90 percent of which are tanoaks and most of the rest coast live oaks. Another 100 million trees may be infected by the insidious pathogen that typically takes one or two years to produce symptoms in the infected trees, he said.
The pathogen can be spread by human footprints and nursery plants, but in nature it rides on water droplets blown from the leaves of bay laurel trees, a host species that abounds among the oak and tanoak trees susceptible to the disease.
Wildlife officials say the northern spotted owl has been listed under the California Endangered Species Act.
The state’s Fish and Game Commission voted unanimously on Friday to add the threatened bird to the list, ending a four-year process by the Environmental Protection Information Center, or EPIC.
EPIC Program Director Tom Wheeler called it a “small step toward recovery.”
Scientists say that owl numbers are now dropping at an annual rate of 3.8 percent. Five years ago, the rate was 2.8 percent.The northern spotted owl was labeled as a “threatened species” under the Federal Species Act in 1990 but the owls’ population has continued to decline. Experts say changing the owl’s status from threatened to endangered could lead to efforts to increase owl habitat on federal lands.
Source: Northern Spotted Owl Added To Endangered Species List – capradio.org