Division of Agriculture and Natural Resources
Division of Agriculture and Natural Resources
Division of Agriculture and Natural Resources
University of California
Division of Agriculture and Natural Resources

Cities in California inland areas must make street tree changes to adapt to future climate

Many common street trees now growing in the interior of California are unlikely to persist in the warmer climate expected in 2099, according to research published in the July 2018 issue of the journal Urban Forestry & Urban Greening.

“Urban foresters in inland cities of California should begin reconsidering their palettes of common street trees to prepare for warmer conditions expected in 2099 due to climate change,” said the study's co-author, Igor Lacan, UC Cooperative Extension environmental horticulture advisor in the Bay Area.

Common trees in Coastal California cities appear to be better suited to withstand the 2099 climate.

Urban foresters in inland cities of California should begin reconsidering their palettes of common street trees to prepare for climate change.

“Our research shows that some trees now lining the streets of cities like Fresno, Stockton and Ukiah are likely to perform poorly in 2099,” Lacan said. “Those cities need to look at the conditions – and trees – now found in El Centro, Barstow and Fresno respectively.”

To reach these conclusions, Lacan and co-author, professor Joe McBride of UC Berkeley, used space-for-time substitution. They compared the most common street tree species in cities representing each of the 16 California climate zones with trees in cities that currently have climates that approximate the expected warmer conditions in the 16 cities 80 years from now.

For example, Eureka can expect a climate like Berkeley's today; Fresno's climate will resemble the climate of El Centro today. (Find the complete list of cities below.) The corresponding cities were determined with climate predictions from Cal-Adapt, which synthesizes California climate change scenarios to reach a consensus view of the magnitude of climatic warming.

Igor Lancan, UC Cooperative Extension urban horticulture advisor. (Photo: Evett Kilmartin)

“We used the mid-range models,” Lacan said. “It's very reasonable to say the warming predicted by the model we used is already ‘baked in,' regardless of any mitigation efforts. While we should take measures to prevent even greater warming – mostly by reducing the use of fossil fuels – this study aims to help adapt California urban forests to the warming that can be reasonably expected to occur.”

Lacan said he and McBride were surprised to find that coastal cities and their warm equivalents contain most of the same common urban tree species, while the warm equivalents of inland cities seemed to lack most and, in some cases, all of the common trees there today.

“It's really a sharp distinction,” Lacan said. “Perhaps they were lucky, but coastal cities are better positioned for the climate of 2099 than the inland cities.”

Climate zone

City

Corresponding city
(approximates climate
in 2099)

1

Eureka

Berkeley

2

Ukiah

Fresno

3

Berkeley

Santa Ana

4

King City

Stockton

5

Santa Maria

Santa Ana

6

Santa Monica

King City

7

San Diego

Santa Ana

8

Santa Ana

Burbank

9

Burbank

Fresno

10

Riverside

Barstow

11

Yuba City

El Centro

12

Stockton

Barstow

13

Fresno

El Centro

14

Barstow

El Centro

15

El Centro

Furnace Creek

16

Susanville

Barstow

For a copy of the complete research report email Igor Lacan, ilacan@ucanr.edu.

Posted on Friday, August 3, 2018 at 8:38 AM
Focus Area Tags: Environment

Comments:

1.
Many Central Valley communities, like Merced, have thousands of coast redwoods as street trees  
boundary or border trees, or just ornamentals. Their popularity is prolific as may be expected  
(state tree) Do you have ‘convincing’ advice for the public and for cities to mitigate this climate  
change-tree preference collision? Thanks. Stan

Posted by Stan Bunce on August 4, 2018 at 6:55 AM

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