Street tree removals are a last resort to protect public safety

By Mohammed Nuru and Carla Short

By Mohammed Nuru and Carla Short

Three years ago, San Francisco voters gave birth to StreetTreeSF, a program that transferred the care of all of San Francisco’s 124,000-plus street trees to the San Francisco Public Works Bureau of Urban Forestry and allocated $19 million annually in dedicated funding to get the job done. This is an enormous responsibility and one we take very seriously.

And as overseer of the street trees, there are times we must make hard decisions – the biggest of which is when it is best to remove a tree.

Taking out a street tree is always the last resort. But if a tree is deemed a risk to public safety, we’ll make the call to remove. We believe this is the responsible thing to do.

Unfortunately, we’re currently in a period where we’re removing more trees than we have in the past. The reason is simple: We finally have the detailed information we need to know which trees are in bad shape and pose a risk. For the first time ever, the Bureau of Urban Forestry has a comprehensive point-in-time census of each street tree in San Francisco. The database tells us the location and species of every street tree, as well as the condition, based on assessments made by professional arborists certified by the International Society of Arboriculture, or ISA.

We use that baseline information to develop a pruning schedule, giving preference to the trees most in need of maintenance right away – the “worst first.” These are trees that pose a safety risk in heavily traveled public rights of way due to such factors as disease or poor limb and/or root structure.

Since the condition of a tree can change between the time it was assessed during the census and when it is scheduled for pruning, each tree is evaluated again by a Bureau of Urban Forestry ISA-certified arborist prior to any work being done. If a determination is made that the tree should be removed, one more assessment is conducted to make sure removal is warranted, with public safety the No. 1 consideration.

Over the last two years, many of the recommendations for removal pertained to ficus trees. In some areas, such as Hayes Valley and 24th Street in the Mission District, there were many ficus trees deemed hazardous. Ficus trees, perhaps more than any other species in San Francisco, are vulnerable to large limb failures that pose safety hazards in public rights of way. We have had numerous incidents of whole ficus trees or large, heavy limbs falling and smashing cars. The two pedestrian injuries from street trees in recent years involved ficus trees. There have been 49 limb failures just on 24th Street between Mission Street and Potrero Avenue over the past decade.

Today, our tree inspectors are in the process of identifying specific trees that are vulnerable to failure near schools, senior centers and corridors with a lot of foot traffic.

Let’s be clear: Not every ficus tree in San Francisco should be removed. When they’re healthy and structurally sound, they provide beautiful canopy. Removal candidates are identified on a case-by-case basis. As our arborists reassess ficus trees citywide, we have found that they are upgrading a large percentage from “removal” status, as identified in the initial census, to “prune” status, which means the problems can be mitigated with pruning.

Our recommendations are methodical and transparent. Again, using 24th Street in the Mission District as an example, we hosted community meetings that were well attended by neighbors and business owners. We’ve connected with Supervisor Hillary Ronen and the neighborhood association, Calle 24. We conducted a community walk-along, going from tree to tree with interested community members to point out the concerns that we found, triggering our recommendations for removals, and we got out word via social media, mailed letters, e-mail and newsletters. We deployed a similar outreach strategy in Hayes Valley. Our webpage with detailed information on ficus trees can be found here:

We always look for alternatives before choosing tree removal or approving a property owner’s request for removal, as with the trees adjacent to the San Francisco Main Public Library. However, removals are sometimes necessary to protect public safety. With the responsibility of care for street trees comes the responsibility for the safety of residents and visitors. If a dying or structurally unsound tree threatens that safety, it is time to remove it.

At the end of the day, we understand the position of people advocating that these removals be stopped. But with responsibility comes hard choices. Our aim at Public Works is to prioritize public safety and grow a healthy and robust urban forest that thrives.

Mohammed Nuru is director of San Francisco Public Works. Carla Short, acting deputy for operations at San Francisco Public Works, is a certified arborist and certified tree-risk assessor.

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