A recently released report found that aging eucalyptus trees in Glen Canyon Park pose a wildfire risk in San Francisco.
Michael Short/Special to the Chronicle
While the risk of wildfires is low across cold and foggy San Francisco, a new report found that aging groves of eucalyptus trees clustered in Glen Canyon pose a potential danger.
The San Francisco Civil Grand Jury, a government oversight panel of volunteer residents, said in a report released Thursday that red flag warnings and Diablo winds create “perfect conditions” for wildfire several days or weeks each year in San Francisco’s urban wildland areas.
But the jury found city efforts to mitigate the risk are disjointed.
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After the Pacific Palisades fire devastated Los Angeles suburbs in early 2025, the grand jury evaluated wildfire risk in Glen Canyon, a recreation area with steep slopes and hundreds of eucalyptus trees.
The jury concluded the eucalyptus trees, an invasive species, are highly flammable and known to explode during wildfires due to their high oil content.
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The trees also shed large amounts of peeling bark and leaves, with the ground around them in Glen Park littered with debris “many inches deep in places,” the report said.
“Our research and interviews led the Jury to conclude that dense stands of unirrigated eucalyptus do present a wildfire risk,” the jury said.
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In particular, trees planted by commercial speculators in the early 20th century — now nearing the end of their lifespan — are “highly vulnerable to wildfire risk,” according to the report.
Mass removal of eucalyptus trees is “not feasible due to their wide dispersion, disposal costs, erosion risk and other factors,” the report said, but coordinated efforts to thin canopies, clear litter and remove diseased or dying trees “is the path of least resistance going forward.”
According to the jury, the city should also replace felled eucalyptus trees with less flammable trees and plant other native species beneath the tree canopy to increase biodiversity and stabilize steep hillsides.
But local agencies with jurisdiction over Glen Canyon “do not devote significant resources toward wildfire abatement,” according to the report, in part because Cal Fire rates the fire hazard severity as low in San Francisco.
Cal Fire previously said parts of the city had moderate wildfire risk, including Glen Canyon and other wooded neighborhoods such as Lake Merced, Stern Grove, the Presidio, Mt. Davidson and Sutro Heights.
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Vegetation management in Glen Canyon is inefficient and uncoordinated because efforts are splintered between four local government agencies, the report said.
The jury recommended that the San Francisco Recreation and Parks Department assume responsibilities from the other agencies to streamline efforts.
The report said city agencies should partner with Cal Fire by using Glen Canyon as an urban training site for removing low-hanging limbs from eucalyptus trees and clearing debris from the forest floor.
The report also recommended that city agencies with wildland properties develop wildfire mitigation plans, share technology and work more closely with the San Francisco Fire Department, which the jury said “takes wildfire risk seriously.”
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