Pity the urban tree. Stuck in a parking lot or sidewalk, hardly ever given enough to drink—it’s no wonder, says May Reid-Marr, project manager at the nonprofit Urban Forest Institute, that city trees tend to look a bit bedraggled. “You can tell they’re a little withered, or they’re much smaller than you’re used to seeing them,” she says. But they’re not bad trees. They’re just the wrong trees for the spot—and, sometimes, for the climate that the city now has.
Trees are declining all over the Bay Area. Oakland, as of earlier this year, hadn’t planted a new sapling since 2008, and has been losing about 6,000 trees each year. San Francisco, despite outspending Oakland by a factor of eight, plants 1,000 fewer trees than it wants to and is one of the least-canopied cities in the nation. Across the Bay, “tree deserts” overlap with historically disadvantaged communities—lower-income neighborhoods with higher pollution scores and higher heat index. Tree health and neighborhood health go hand in hand: pollution, asthma rates, and even high blood pressure are lower in places with more urban trees. But the poor conditions for trees in hot spots are only getting worse as the climate warms. “A lot of trees can usually survive if they get enough water—but they’re not going to thrive.” says Reid-Marr. We’ve picked the wrong trees, she says.
A prime example is, unfortunately, the most popular street tree in the area and one of the most common in the nation: the London plane, which requires moist, well-drained soil to thrive. Poorly adapted trees are “more vulnerable to diseases, won’t create a good canopy, won’t reach their full size,” Reid-Marr says. They’ll need more upkeep just to live. “A lot of trees in California that are planted do not make it to the 10-year mark.”
Stitching up our patchy urban canopy is a national concern—and one Congress allocated $1.5 billion to in the 2022 Inflation Reduction Act (IRA). Thirteen Bay Area cities and local organizations are receiving a total of $42 million from the U.S. Forest Service, about half of the $104 million granted to California. This money gives cities the chance to replant much of what has been lost—hopefully with climate-resilient species. That’s where Reid-Marr’s organization comes in; the Urban Forest Institute, based in San Luis Obispo, was granted $3.8 million to help Californians zero in on the right trees for the job, whether for city plantings, commercial developments, or private backyards.
“We’re here to help them choose trees that are going to thrive in their region,” Reid-Marr says. Her team uses localized models of California’s climate future (current forecast: hotter, drier), and looks for trees with matching native climates in a huge, global database. More sun and less rain might make the Bay Area a good place for SoCal locals such as the Engelmann oak (Quercus engelmannii), with its leathery leaves and wide canopy, or Aussies like the swamp mallee (Eucalyptus spathulata) with its fragrant summer blooms. We might turn to the South American pepper tree (Schinus molle), which produces fruity pink peppercorns and attracts bees (and lines the street on which Bay Nature’s offices sit). From China, more pistache trees (Pistacia chinensis) could be planted to inject a bit of fall flavor to the Bay Area with their bright red-yellow gradient and clusters of reddish fruit.
But picking a city tree is complex, in part because the tree itself can be picky. How much salt spray it tolerates, what kind of soil it needs, and whether it mingles well with nearby fungi—all varies from tree to tree. We, too, are picky. How tall can it grow? How much shade will it give? Will birds nest in it? Is it toxic for our pets (or us)? Any chance it might become invasive?
This story is part of Wild Billions, a Bay Nature project exploring the impact of big federal money on Bay Area nature.
More on urban trees in this series:
• Oakland’s Urban Tree Dreams Get (Partially) Funded
• As Cities Heat Up, USDA Grants $42 Million for Urban Trees Around the Bay
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Previously, UFI and UFEI (the Urban Forest Ecosystems Institute, an initiative of California Polytechnic State University) partnered to make SelecTree, an online tool that helps people pick trees by desired attributes, including whether it’s climate-adapted for a particular zip code. Now, with the new grant funding, Reid-Marr plans to update the database, making sure the recommended trees are up to task. On the website, you can find specialized lists curated by ecologists, like this one for large climate-adapted trees for the Bay Area.
PLANT SOMETHING
Free Trees
Nonprofits and some city governments offer free or very cheap trees. Here are some places you can call (and email us at editorial@baynature.org if you know of others):
San Jose/South Bay: Our City Forest
Midpeninsula: Canopy
San Francisco: Friends of the Urban Forest
South and West Berkeley: Trees Make Life Better (City of Berkeley)
Oakland: Trees for Oakland (has a $150 donation request)
Whatever new trees we decide on, we still have to get them in the ground—another challenge, because plant nurseries are on the front lines of a native seed shortage, and have to plan years in advance to make some tree species available. Many oaks, for example, would make great trees in the Bay Area, Reid-Marr says—but must be grown in nurseries for several years before they can be planted and safely left to their own devices. So in addition to finding the right species, UFI will use part of its grant funding to coordinate the relationship between city planners and nearby nurseries.
In most places, Reid says, the urban canopy doesn’t need to be changed dramatically. “Trees that are doing OK, if they’re in place already and they’re surviving great—great, they can stay there,” she says. The hope, though, is to make future planting decisions easy for everyone to make.
Update Aug. 15, 2024: The Engelmann oak drawing has been updated; it previously noted that this tree is toxic. That is true, if eaten raw. But the acorns are yummy if processed properly, and have long been documented as a traditional food source for Indigenous groups in California.
Update Sept. 10, 2024: Added Canopy to the list of groups offering free trees.
