Rot Spotter: Marin County arborist Ken Bovero inspects a tree in St. Francis Wood for Sudden Oak Death.
Life and Limb
What’s killing North Bay trees? Just about everything
By Tara Treasurefield
The majestic oak tree in Dub and Lyn Hay’s backyard is estimated to be more than 300 years old. Growing beside Sonoma Creek on the east side of Sonoma, the towering oak makes the yard a cool refuge on blistering summer days. Throughout the year, its sheltering presence offers a calm retreat from the world’s woes.
Some of the oak’s branches extend all the way to the property line and over the back fence. To prevent their elderly neighbor’s inheritors from lopping off the errant branches, the Hays hope to have the oak protected as a heritage tree.
This is one lucky oak. But it’s by no means safe. For trees of all ages and types, the world seems to be an increasingly dangerous place.
Sudden Oak Death has killed tens of thousands of oak trees from Monterey County to Mendocino County. But oaks aren’t the only ones at risk: This January, Marin County arborist Ken Bovero sent shock waves through Northern California when he announced that he had found SOD on two dying redwoods.
“University researchers informed me that they already knew it was in redwoods,” Bovero says. “I was surprised that they didn’t let people know.”
As it turns out, the fungus that Bovero found isn’t the same species as SOD. But now the public knows what university researchers knew before Bovero’s announcement: The SOD pathogen is sometimes present on redwood sprouts.
Bearer of bad tidings that he is, Bovero brought SOD to the attention of state and university scientists way back in 1991. “They disregarded it for a long time,” he says. “I was seeing it spreading throughout Marin, and they didn’t feel it was a problem.” Finally, in 1995, Bovero and his friend and colleague Ralph Zingaro went to the press.
Establishment scientists and Bovero still seem to be on different pages regarding the disease. “My feeling is that it will spread and that we’ll continue to see decline in redwoods,” Bovero says.
Susan Frankel, plant pathologist with the USDA Forest Service, says that overall, Muir Woods looks good. “We don’t see any real damage to redwoods,” she says. “We don’t have any indication that anything but the sprouts are affected.”
So far, redwoods have eluded the SOD quarantine that went into effect Feb. 13. But University of California scientists are still conducting tests, and may yet add redwoods to the SOD host list. If that happens, it could become illegal to ship the bark or mulch of redwoods, and each redwood may have to be inspected before it’s shipped.
“It will be a lot of work for regulators and the timber industry,” Frankel says. “The Forest Service is concerned about doing whatever it takes to protect the forests. But we don’t want to be unreasonable and create economic hardship.”
“The trees in the North Bay are really in trouble,” says Lynn Hamilton, a founding member of the Town Hall Coalition, a Sonoma County environmental organization. “I’m looking out the window at a redwood forest, and I’m worried about what I see. The forest is not healthy.”
Hamilton is also grieving for oaks. “In Marin County, I walked through the hills around Fairfax and saw that at least three-fourths of the oaks are dead,” she says. “Sudden Oak Death is everywhere. I have seen hundred-year oaks fall to the ground. The whole watershed in Marin County is beige. It’s devastating.”
Under a contract with the Forest Service, plant pathologist Ted Swiecki studied SOD in Glen Ellen’s Jack London State Historic Park. “The percent of trees affected by SOD is relatively low, but there are a lot of stands that aren’t exactly at the peak of health,” he explains. “There are a lot of other tree diseases out there.”
Insects also wreak havoc on North Bay trees. Codling moths, aphids, fire blight, apple scab, and powdery mildew gang up on apple trees. After nearly polishing off birches in Sonoma County, the voracious bronze birch borer is now sampling the cuisine in Marin. Between 1995 and 1996, Dutch elm disease tore through the elm population, and it’s still active. The long horn borer is feasting on eucalyptus trees.
Pine pitch canker has killed so many Monterey pines that this ill-fated tree may disappear altogether. In inland areas such as Santa Rosa and San Rafael, Monterey pines are doubly cursed, afflicted with both pine pitch canker and deadly bark beetles. If wishes were horses, the Monterey pines of the North Bay would probably be galloping back to Monterey, where their chances of survival are slightly better.
Root of the Problem
Which of these myriad threats pose the worst menace to trees? Soil health, global trade, and land use are at the top of the list, according to local experts.
Trees are what they eat, says arborist Ralph Zingaro. “Air pollution acts as a natural herbicide to trees,” he says. “It actually leaches valuable nutrients from trees and soil. The trees are starving to death.”
“We’ve done a lot of nutritional sampling on thousands of trees, mostly oaks,” says Zingaro, a member of Bioscape, a group of licensed “plant doctors on call” funded by a landowner with 500 acres in West Marin to look into SOD. “Now we’re beginning to test the redwood. Once the soil becomes acidic, which it is–we’re getting acid rain–the phosphorous is completely unavailable. Trees need phosphorous in order to grow and function.”
Zingaro says that injecting trees with phosphite fertilizer boosts their nutritional status and makes them healthier. “It’s not a treatment for SOD, but we all know that healthy trees don’t get sick,” he says.
That kind of talk irks some tree experts.
“It’s baloney to say that you can protect trees from Sudden Oak Death by keeping them healthy,” says Bruce Hagen, urban forester at the northern regional headquarters of the California Department of Forestry and Fire Protection. “Trees that are susceptible to SOD and are exposed to it get it, no matter how healthy they are. The best way to prevent SOD is chemically, with copper sulfate.” Hagen hastens to add, however, that keeping trees healthy does prevent other serious pest problems.
Like Zingaro, Elaine Ingham, associate professor of botany and plant pathology at Oregon State University, stresses soil health. “Our soils are under attack, and we are the enemy attacking them,” she says.
“We have killed the beneficial organisms almost everywhere,” Ingham says, including along roadsides, in agricultural fields, and even in national parks. “Fumigated fields have only disease and pest organisms growing in them.”
Repair is possible. Worm castings restore soil health, according to Ingham. “It doesn’t solve global warming or air pollution or loss of the water table,” she says. “But it will save the trees.” Apparently, insects and fungi know when the jig is up. Studies show that they avoid worm castings.
But reaching for the nearest pesticide is a common reflex, according to Pavel Svihra, horticulture advisor at UC Cooperative Extension in Marin. “When people call for help with their trees, we always give alternatives of chemical and nonchemical solutions,” he says. “Most people choose the chemical option.”
“I don’t want to start some rant about global trade, but based on the evidence we have right now, SOD probably came from another part of the world,” says Steven Swain, Sudden Oak Death Project Coordinator at UC Cooperative Extension. He explains that a large proportion of the trees attacked by a new pest have almost no resistance.
The good news is that genetic resistance develops naturally, since it’s resistant trees that survive and restock. But in a world where impatient humans call the shots, there’s also bad news: Nature works her magic at the speed of a snail with its brakes on.
“Our global economy has been introducing serious new pests every year,” says Swiecki. “With people moving material around, you have the constant threat of new diseases and insects being introduced.” Worse yet, invasive species like broom and star thistle tend to take over and crowd out native species.
To support native trees, says Hagen, “Take your cues from what is growing naturally around you. Plant native trees in the same percentages, on a random basis.”
If Swain had his way, all new materials coming into the country would be monitored, as he says, “to make sure that people don’t bring in nasty pathogens.”
Not Exactly Natural
Of course forests are dying. Of course trees are dying.
“People tend to think of forests as a static thing, but all along, forests have died and moved and shifted,” Swain says. “However, we have complicated things.”
Examples of this interplay between disease and human behavior abound.
Along with root rot and other insults, Sudden Oak Death clobbered China Camp in Marin, which was probably clear-cut around 1890. Jack London State Historic Park was logged several times over, and it has also been hard hit by SOD and other diseases.
When a whole stand is cut down, the trees that sprout up to replace it are all in the same state at the same time, Swiecki says. That lack of diversity can prove deadly: In such cases, disease can kill an unusual number of trees.
Also, trees that grow out of stumps are more susceptible to root decay and may have a shorter life than trees that grow from seeds. “No one was thinking about this 150 years ago when they were looking for gold,” Swiecki says.
Modern-day prospectors are equally clueless. Since 1945, 1.5 million acres of oak woodlands have been converted to other land uses or fragmented by development. In 1996, the Forest Service reported that between 1984 and 1994, Sonoma County lost 38,000 acres of timberland to urban conversions and agriculture. Today, Sonoma County vineyards alone occupy 56,000 acres, most of which were originally forest or woodlands.
“Developers are bulldozing large areas of the mixed forests of the Mayacamas Mountains,” says Marilyn Goode, a member of the Sonoma Mountain Preservation Group.
Similarly, Swiecki points to urban expansion in Marin County. “Where [development] goes into existing woodlands, carves them up, takes out trees, puts in invasives, you’re causing more problems,” he says.
Conserving existing resources is always better than trying to re-create them, Swiecki argues. “Leaving things alone is a large part of helping out,” he says. “The first thing is to do no harm. There are many more ways to damage forests and trees than to help them.”
Ye Gods & Little Salamanders
Of course, it’s not just trees at stake in the battle to save California’s forests. “We haven’t seen many tent caterpillars for more than 10 years, and they’re a food source for many birds,” Goode says. “There’s been a reduction of everything, including birds, snakes, the California newt and other salamanders, and even the lowly banana slug.” This is partly due to lost habitat, according to Goode.
It works both ways. When protected species lose their protection, so does the land they occupy. “We’ve got an administration hoping to turn back the Endangered Species Act,” says Hagen–and that’s bad news for forests and woodlands.
Forests also face threats in the California legislature. Assembly bills 985 and 1561 propose to de-list 37 species protected by the state’s Fully Protected Species Act. Nine of these species depend on oak woodland habitat for their survival. “They were listed in the first place because they had lost critical habitat,” says Janet Cobb, president of the California Oaks Foundation.
The legislation sprang out of obstacles posed to developers and state officials by an endangered lizard, according to David Bunn, deputy director of legislative affairs for the California Department of Fish and Game.
“AB 985 came about during the development of a Habitat Conservation Plan for the blunt-nosed leopard lizard, a fully protected species,” Bunn says. “We could not issue a permit for the incidental [killing] of a fully protected species.”
A kind of tit for tat, a Habitat Conservation Plan allows Fish and Game to sacrifice endangered species and habitat for a specific development project. In exchange, developers contribute to “regional or area-wide protection of plants, animals, and their habitats.” An HCP isn’t possible with fully protected species, which cannot be sacrificed.
Whether or not HCPs serve the greater good is hotly debated by environmentalists and developers.
But two recent government actions are clearly harmful to trees: the Environmental Protection Agency’s decision in December to exempt the agriculture and dairy industries from the Clean Air Act; and the Bush administration’s plan to allow parts of the nation to ignore the “roadless rule” in national forests.
“As a person who understands science and limited resources, I don’t think that politicians can make wise decisions about biology and ecology. They only know compromise,” Hagen says. “High-school teachers would do a better job of managing our resources than our politicians do.”
“It really relates back to people,” Lynn Hamilton says. “It’s not just about trees. It’s about life. Preservation of life.”
From the February 21-27, 2002 issue of the North Bay Bohemian.