In San Francisco, A Dying Forest Waits for Action

July 23, 2014

Walk a few feet into the jungle on the west side of San Francisco’s Mount Sutro Open Space Reserve, and you’ll come to an unusual three-headed eucalyptus tree. Its single trunk is firmly rooted, and three trees sprout tenuously from the base, limbs stretching out away from the prevailing west wind and into the tangle of brown-and-green that dominates this 61-acre open space area.

We’re standing to the left of the trunk as a group of four cyclists pauses to study the Cerberus and debate their route. The apparent quirk of nature is an unexpected gift during their workout—they glance at the tree, they glance at their phones, they glance at the tree, they glance at each other, they glance at the tree.

Craig Dawson, meanwhile, just gazes at the tree. He stands at its base and surveys it and its surrounding plant life, gently probing the bark like a doctor searching for a diagnosis. To Dawson, who knows this place as well as anyone, the tree isn’t some kind of poetic, natural rebellion — it’s a sign that the forest is sick. The extra stress of multiple “heads” drains the tree’s main trunk of its water supply, turning what is referred to by Dawson as a “moisture sweet spot” into a stilled heart that will eventually give way to deep splits. Splits lead to breakage; breakage leads to limbs that crash to the ground with a sound Dawson likens to a clap of thunder. Sutro Forest is quickly becoming a hazardous place for hikers and bikers who want to escape the city without leaving it.

“If you hear something crack above you, just move quick,” Dawson says. “They call these falling branches widow-makers for a reason.”

Craig Dawson, executive director at Sutro Stewards, says that the forest cannot remain in limbo much longer without posing a real threat to its visitors. Photo by Becca Andrews.
Craig Dawson, the executive director of Sutro Stewards, says that the forest cannot remain in limbo much longer without posing a real threat to its visitors. (Photo by Becca Andrews)

Sutro’s once-thriving blue gum eucalyptus trees are dying for a variety of reasons, including age and drought, both of which make the trees more susceptible to disease, pests, and fire. And there are likely other causes yet to be identified by the master arborists and biologists studying the forest. But the foresters generally agree that time is running out for this urban forest, which is owned and managed by the University of California, San Francisco. At the moment, though, the university does not have an approved environmental impact report for maintenance, and in the absence of major work conditions are deteriorating fast. Dawson’s eight-year-old nonprofit, Sutro Stewards, has built and maintained trails through the forest, and performs some small-scale tasks, but the Stewards’ resources are limited. Attempts to come up with an updated management plan have stalled, so for now the Sutro Forest remains in limbo.

Until the late 1800s, the centrally located prominence that would soon be named Mount Sutro was covered in native coastal shrubs, grasses and wildflowers. It was most definitely not a forest. But Adolf Sutro, at the time the mayor of San Francisco, owned the hill, and a forest was what he wanted on his hill. So in 1886 he planted imported blue-gum eucalyptus and other fast-growing non-native trees  in honor of Arbor Day. Sutro’s efforts 130 years ago birthed the modern forest, which is problem number one: The typical life span of a blue gum eucalyptus in California is about a century, Dawson says. But that’s not Sutro’s problem any more. In 1895, Sutro donated 13 of Mount Sutro’s acres to UCSF, and the university bought another 90 acres that included the rest of the hill in 1953. Since then, UCSF’s relationship with the area, and its attempts to come up with a plan for it, have been complicated by the passionate voices of community members who have become invested in their local open space but who don’t necessarily agree on how it should be cared for.

The Sutro Stewards, along with a handful of master arborists, thought they had a workable plan in January 2013, when UCSF released a draft EIR that announced intentions to reduce the fire risk by thinning the forest and removing the dying eucalyptus trees. That plan, however, was met with fierce opposition from people who considered the removal of trees—any trees—as destruction of their beloved forest. The draft document received more than 300 comments, many of which argued that nature should be allowed to take its course in Sutro Forest. The uproar effectively stymied further action: In November 2013, the university announced that it was planning for a new EIR taking an entirely different approach and managing the forest solely for fire danger (mainly by bulldozing particularly dangerous areas); in February 2014, a university spokesperson said that that EIR had been withdrawn, and that work on the original draft EIR was continuing. UCSF’s website states that the delay is due to an “unforeseen workload.”

Damon Lew, UCSF’s assistant director of community relations, says master arborist Kent Julin is helping the university draft a new EIR, tentatively slated for release this fall, that will address all 300 comments. Julin says he can’t discuss the new report’s progress, but says that the state of Sutro Forest is grim. Invasive species like blackberry and English ivy are overwhelming the ecosystem and choking the previous inhabitants—and, more importantly, creating a severe fire hazard by collecting “fine fuel” like twigs and leaves. Typically, in a forest like this, a disturbance of some sort—like a fire—would clear the thick understory and allow new trees to grow. But fire isn’t an acceptable management option in a densely populated city where local firefighters have more experience with burning buildings than  forest fires,

But some now argue that never mind an intentional, controlled burn: the entire area could go up in an uncontrolled blaze. Longtime San Francisco city gardener, native plant advocate, and Sutro Steward volunteer Jake Sigg sees fire as a distinct possibility in the city’s drought-stressed, sick eucalyptus groves.

“People find it hard to credit the possibility of a fire in these areas,” Sigg wrote in his Nature News email newsletter on June 10. But he describes stumbling into a chest-high pit of dry fuel five years ago and having an “epiphany” about the alarming level of fuel accumulation in the forest. “The long strips of annually-shedding blue gum bark have been known to carry fire 12 miles, enough to carry glowing embers from San Francisco to the East Bay hills,” he wrote. “At the risk of sounding alarmist, it is not unrealistic to portray a scenario of a rare General Alarm fire.”

Julin says he agrees, especially given this year’s drought. “On any given day in the summertime, if there’s no fog, there’s a potential for a fire.”

Although UCSF does basic fire prevention maintenance—last summer, workers cleared vegetation away from the roads through the grove and this year cut back growth from campus housing and other UCSF structures— Dawson and Julin say they worry it’s not enough. “The issue that we have been talking about for 16 years has suddenly come to a boil,” Dawson said. “There’s no question these trees are sick, there’s no question whether these trees are going to survive—they are not—and this [current state of the forest] is a game changer.”

As he walks through the forest Dawson gestures at thick ivy and blackberry vines that  snake their way up pale tree trunks. Among other impacts, the brambly mess makes it difficult for birds of prey, such as the great horned owl, to hunt rodents, forcing the birds to  the forest’s outer edges. A dead tree catches Dawson’s eye. The trunk, barely visible through the thick green net of ivy, is huge, but as it stretches into the sky, the branches are smaller and bare. The only green is the emerald of the ivy, and the only sign of the former canopy is the skeletal remains of dead eucalyptus.

“Look at that, that’s all ivy, the tree is being supported just by ivy,” Dawson says.

The problems have become so great, the tangle in the forest so dense, that there is no easy solution. Bulldozers can temporarily clear away blackberry and ivy, but that also spreads  the seeds, ensuring the invasive plants will come back just as strong. Eucalyptus themselves are notoriously difficult to remove: cut the trunk off and they will resprout if not treated. Bag the trunk to prevent regrowth and the tree can resprout in multiple places, all along its roots. Poison the tree and it will suck up the poison and send it out into its roots, killing everything around it. To remove a single tree can cost thousands of dollars; multiply that by the 45,000 (or so) trees in the reserve.

Back at the foot of the three-headed tree, the cyclists decide to take a trail that veers off in the opposite direction of the unnatural phenomenon. They zip off through the trees, calling back and forth to each other. A few joggers also pass by, earbuds in, enjoying the breeze filtering through the forest. Dawson and I pick our way back through the dense understory, listening carefully for the slightest hint of a cracking branch.

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