Map of Mt. Sutro and Interior Greenbelt. The darker shade of green is the Interior Greenbelt under the jurisdiction of the SF Recreation & Parks Department. The lighter shade of green is under the jurisdiction of the University of California at San Francisco.
By Thomas K. Pendergast
(Originally published in the October, 2016, issue of the Sunset Beacon newspaper, a community newspaper serving the Sunset District of San Francisco.)
There are two plans for dealing with the blue gum eucalyptus trees on Mount Sutro, and they appear to be going in opposite directions.
The San Francisco Planning Department and Recreation and Parks Department will be cutting 140 of the trees down in the Interior Greenbelt section of the forest they control on the east side of Mr. Sutro, near Stanyan Street.
Meanwhile, University of California at San Francisco (UCSF) officials recently announced a plan to plant more of the non-native trees on the land they have control over.
The 20-year plan for the 61-acre reserve behind UCSF’s inner Sunset campus will be executed in four phases, each taking about five years to complete.
Matt Greene, a consultant on the Mount Sutro Technical Advisory committee (TAC), said the forest density varies, with a range of 45 to 270 trees per acre.
“It was a pretty big range there. That’s why we actually separated out different vegetation types, so we could capture those different micro-climates and those different areas within the reserve,” Greene said. “Forest Type 1 has the most trees per acre. It’s also got the most dead trees per acre. It has 270 trees per acres (plus) over 100 dead trees per acre standing right now.”
Greene also said about a quarter of the trees on the reserve have less than 25 percent of their “life crowns,” indicating that they are not healthy.
“Those trees aren’t dead. We aren’t writing them off, but we’re really worried that they’re not going to make it through an extended drought, if that’s what we’re really heading into.”
So, the initial phase will focus on removing dead, dying, unhealthy and structurally unsound trees; controlling low-growing vines and shrubs that compete with more desired vegetation; and, planting new trees, including four acres that will be replanted with blue gum eucalyptus.
Six years later, they will begin phase 2, which will also remove dead or dying trees and replace them with blue gum and other species of eucalyptus trees.
Greene said a 2001 report estimated that 12 percent of the trees standing were dead. In 2016, they estimated 23 percent were dead.
“We’re seeing a higher mortality rate and that’s really frightening to see that mortality rate climb,” said Greene. “The stand is too dense. We have too many trees per acre right now. If you go to the Presidio, they’re running somewhere between 45 and 100 trees per acre…. There’s just too many trees to really have a healthy forest at this point in time.”
Furthermore, he said, they have found “no real evidence” that the forest is regenerating itself. The under-story vegetation of Blackberry and Ivy is restricting new trees from coming up through that dense layer and getting established. In forest type 2 and 3, for example, there is almost no regeneration; all the small trees have completely died off.
An inventory earlier this year estimated there are around 3,400 dead and 10,000 live trees within the reserve.
“Initially we’re going to start with blue gum because we have to try and regenerate blue gum on this site,” said Jim Clark, another TAC consultant. “There’s a very significant set of stakeholders who want Mt. Sutro to continue to be a canopy of blue gum eucalyptus. I think that’s why you’ll see, through our plan, that our first steps are trying to regenerate the species that we have and then later on expanding the species pallet to different tree species.”
One stakeholder who does not want to see more eucalyptus is Jish Brown, who lives in the neighborhood. She sees them as potentially giant Roman candles in the event of a fire.
“I would like to see the blue gum eucalyptus eliminated anywhere near houses because … it is my understanding that in a fire the flames from the eucalyptus are double the size of the tree,” she said. “They are dangerous.”
Richard Sampson of Cal Fire responded to her concern.
“In the right conditions you could see that happening, but the main thing is how often are you going to see those conditions? So, the question before the consultants is: What do you plan for? Do you plan for the worst-case scenario? Do you plan for what happens every day? And that’s what they have to decide,” Sampson said.
Denise Louie of the California Invasive Plant Council, which she described as a “state-wide, science-based group,” also criticized the replanting of eucalyptus.
“Our mission is to identify and educate people about plants that we should avoid and remove. And to be sure, eucalyptus is one of those plants we should remove and avoid,” she said. “So I’m quite surprised, and I’m incredulous that it appears to be a plant you want to put into the ground in San Francisco. I encourage you to rethink this.
“San Francisco is a very important part of the biodiversity hot spot that is California and we have native species of plants and wildlife that belong here, that are at risk of extinction, that are not found in the wild outside of California…. So I want to encourage you to rethink this idea of planting more eucalyptus on this hill.”
Another skeptic of the plan is Craig Dawson, the executive director of Sutro Stewards, a group now engaged in replanting parts of Mr. Sutro with native species.
Dawson said it is important to look at the history from the last 100 years to understand the present situation. The trees on the 909-foot-tall hill date back to 1886, when mining magnate and former SF Mayor Adolph Sutro planted the slopes with eucalyptus, Monterey pine, Monterey cypress and fruit trees. The eucalyptus appear to have been the most successful at taking root.
“We have a eucalyptus plantation. A plantation is a man-made entity,” Dawson said. “Adolph Sutro never envisioned a eucalyptus forest. He only planted the eucalyptus to screen the harsh winds coming off the Pacific Ocean to protect the other trees that he put into this forest. His plan was to remove the eucalyptus when the other trees could stand on their own.
“(It was a) failed plan to begin with and that’s why we ended up with the eucalyptus plantation we have today,” he said. “There is disease in this forest. There are pests in this forest.”
Dawson explained that he and others with the Sutro Stewards have dug down into the soil all over Mt. Sutro.
“And I can tell you we don’t get very far, maybe two inches on a good day, and we hit dust, and we hit rock. The water does not penetrate. Those are problems that are not going to go away whether you plant new eucalyptus or anything else out there. So I think we need to look and examine a little bit more what the causes are behind the existing conditions,” he said.
“When we think about diversifying a forest for its health, we really, truly have got to get beyond talking about planting a failed experiment that we have now,” Dawson elaborated. “And I’m sorry. I want to encourage you to do the right thing. I cannot support the planting of Blue Gum eucalyptus. I can only support a very strong and quick effort to diversify this area.
“We won’t be around to see the result of that because trees grow slowly but I want you to do it for my children’s children.”