Which neighborhoods in Berkeley are graced with the lushest tree canopy? And which neighborhoods suffer from relatively paltry tree coverings and all the attendant woes – aesthetically lacking streets, harsher air pollution and an unpleasant heat-island effect?
The answers are revealed in a series of maps produced by the national nonprofit American Forests, which assign neighborhoods “tree-equity scores” based on existing canopy cover, population density and socioeconomic factors like race and income. As one would expect, in Berkeley the richer areas in the hills and north enjoy high tree scores, while more diverse and lower-income communities to the west and south are still playing catch-up.
American Forests, the oldest national nonprofit conservation organization in the U.S., embarked on the project so “every advocate within cities can have access to this information and use it to help them make the case for improving their neighborhood and tree-equity score,” said Chris David, the organization’s director of technology. (In addition to the Bay Area, the group has mapped Seattle, Houston, Detroit and several other urban areas.)
“The general trend you see is that trees grow on money. In many cases, the wealthier parts of town are the most forested,” said David. “We think that is structurally unfair, and it’s important that cities are able to see where they’re not investing enough for their residents.”
The calculations underpinning the equity scores might appear mathematically knotty: for example, “Ni = (xi – xi,min) / (xi,max – xi,min), where, for each indicator, Ni, xi is the value for that neighborhood for that indicator.”
Basically, the scores are looking at where a neighborhood’s canopy should be compared to where it’s at today, with an emphasis on leveling the playing field for disadvantaged communities. For that reason, the calculations weigh demographic data on poverty rate, percentage of nonwhite people, the ratio of seniors and children to working adults, and urban heat-island severity. (Read more about how the tree equity score is calculated.)
Berkeley’s 100% and 90s scores – correlating to neighborhoods that have achieved tree equity – cluster north of the campus and in southeastern enclaves like the Elmwood. Places with scores in the 70s or even as low as 49 run along the waterfront, in light-industrial areas and near the Oakland/Berkeley border. By clicking on the neighborhood blocks you can see their demographics and average surface temperatures, which are based on summer highs.
“We look for the hottest summer temperatures because those are the days when we are most likely to see heat-related health impacts,” David explained. “We want to see the impact the urban form (read: impervious cover like roads, buildings, driveways, and parking lots) has on generating excess heat on hot summer days.”
As it happens, help may be on the way for Berkeley spots with poor tree equity, particularly those west of San Pablo Avenue and south of Ashby Avenue. The city of Berkeley plans to plant 1,000 new trees in these locations in the next two years and has secured funds for half of them from a California Natural Resources Agency grant worth $726,000.
“We’ve noticed there are certain sections of the city that have fewer trees than others. We wanted to address those, and that’s what this grant specifies,” said Dan Gallagher, a senior forestry supervisor with the city.
“The unique part of this grant is it not only allows us to plant trees, but we can make tree-planting locations. We can create the spaces for the trees to be planted by cutting concrete out of the sidewalk,” he said. “It also pays for watering. Historically, we’ve been somewhat limited because the watering is the most challenging part of having a tree planted. You need three summers’ worth of watering to have the tree survive.”
The city is applying for another grant to fund the remaining 500 trees, which in this case would require residents to water them for the first few years. But paying for 20 gallons of water a week to nurture a sidewalk tree might be something people are OK doing, hopes Gallagher.
“The point I want to make to any property owner is that it’s been proven that a tree will increase the value of the property significantly,” he said. “There are environmental benefits, health benefits, socioeconomic benefits, and you have cost savings because the tree shades your home so you’re not so hot in the summertime. There are a lot of benefits to having a tree in front of your house.”
The city of Berkeley currently has a “municipal forest” made up of 38,000 street, park and median trees. They are maintained by the urban forestry unit of the parks division.