Could the iconic sci-fi palm trees disappear?

English

It is hard to imagine Dolores Street or Embarcadero without palm trees. Somehow symbolic of glamour, relaxation, and the Californian lifestyle, these towering, leafy pillars are practically synonymous with the Golden State.

And yet, a recent report on the loss of an iconic palm population in Los Angeles and a tree-mageddon caused by two-week atmospheric rivers and bomb cyclones makes us wonder: could pests, changing weather patterns, and changes in public policy eventually lead to the extinction of palm trees? San Francisco?

Palm populations in Los Angeles are rapidly declining due to three major threats: weevils, fungi, and the city’s preference for native plants (the only type of palm native to California is the Southern California fan palm). Looking into how SF palms deal with these issues also begs the question: should they even be here?

Weevils

According to the Los Angeles Times, the South American palm weevil is the most destructive palm insect. Date palms of the Canary Islands are most susceptible to palm weevil, and we have 587 of them in San Francisco.

Those beautiful palm trees framing Dolores? These are the date palms of the Canary Islands, so beloved by the city that the city has officially recognized them as trees with landmark status. Yes, it’s a thing. According to Scott Wheeler, manager of The Urban Arborist, of the city’s 40 “legacy” trees, 25 are palms.

But despite their heritage status, palm trees are not native to San Francisco, and that creates its own problems.

“Introducing non-native plants like palms can be very problematic because they bring their own pathogens and pests with them,” said Eddie Bartley, president of the California Native Plant Society.

Luckily, we don’t see much palm weevil in San Francisco, and according to Wheeler, nurseries from Southern California are being quarantined before arriving in the city.

Fungus

Fusarium fungus poses a big threat to San Francisco palm trees. Once the palm is infected, it cannot be eradicated.

Complicating matters, Wheeler says, is the fact that Fusarium is released through spores, and the wind can carry the spores to nearby trees when an infected tree is cut down.

A Fusarium outbreak affected some of the Canary Islands date palms on the Embarcadero in 2013 and the dead trees were replaced with hardier palm species. This local outbreak has not yet spread to other palm trees in the city, but it is always possible.

Storms

Our palms may be (mostly) protected from fungus and weevils, but what about recent storms?

In January, heavy rains and strong winds caused over 300 trees to fall across the city – up from 27 trees in the whole of December – so you have nothing to worry about.

And yet palm trees have proven remarkably resilient. Despite their shallow roots and grass-like trunk (technically palms are not trees at all), they are difficult to topple.

“They handle storms well,” said Joe McBride, professor emeritus of landscape architecture and environmental planning at the University of California, Berkeley. “Palms have adapted to higher wind speeds.”

San Francisco’s iconic palm trees seem safe so far, and the city is doing its best to protect them. The historic palm trees on Dolores were surrounded by plastic mesh during recent street renovations to keep tools and equipment from being placed close enough to the ground to damage their root systems, Wheeler said.

Are there palm trees?

Palm trees aren’t native to San Francisco — they first arrived in the city in the 1700s when Spanish missionaries planted them to use in religious ceremonies, McBride says.

The palm trees lining the streets of San Francisco came into existence centuries later thanks to civic projects such as the one that planted them along the Embarcadero after one of the biggest disasters in the city’s history. “They were supposed to symbolize the rebirth of the city after the Lomo Prieta earthquake,” McBride said.

But such efforts have not been without criticism. “As mayor, [Gavin] Newsom has spent millions planting palm trees,” Bartley said. “It caused a long debate about what belongs here.”

According to Joshua Clipp, an urban forest advocate who has volunteered for 12 years with Friends of the Urban Forest, palm trees have little to offer in terms of climate resilience because they don’t store much carbon and don’t provide much shade.

“They look like a thin cotton swab,” Clipp said.

Given that San Francisco has the smallest urban canopy of any major city, Clipp says other trees might make more sense.

“Palms were removed from the approved list of street trees two or three years ago,” Clipp said. So when a non-legacy street palm dies, the city will not replace it with another palm, but that does not stop them from growing in parks or private property.

Meanwhile, San Francisco’s urban cover continues to shrink, despite planting 30,000 street trees by 2024 as part of the city’s climate action plan.

“We are not planting half as many trees to keep up with the rate of clearing,” Clipp said. “We are moving in the opposite direction from where we should be moving.”

English