Street Trees and Climate Change

Instructions and Suggestions
for using Space-for-Time Substitution to assess suitability of urban trees for a changing climate

1. The background and rationale for the method – space-for-time substitution (STS) – to assess suitability of urban trees for the changing climate is described in the 2018 McBride and Lacan article. DOI:10.1016/j.ufug.2018.07.020

2. A summary of this information is provided in the presentation for UC Master Gardeners, available on this website. Other options are discussed in the presentation.

3. The instructions assume that the user in on the West Coast of the United States.

4. Here is an overview of the required steps:
   1. Write down the tree species which you are interested in assessing, the “tree species of concern.” An example table for this is provided below.
   2. Determine the future projected climate for your city. A simple way to do this is to consult the Climate Explorer https://crt-climate-explorer.nemac.org/
      1. Enter your city
      2. Click on “Climate Graphs”
      3. In the top row, select “Monthly” graph type.
      4. Ensure that the box on the left shows “Average Daily Maximum Temperature” (or: select another metric, if you prefer. But the average max temp data are commonly available, so it makes for simple comparisons).
      5. Below the graph, select the desired time horizon (2010-2040, 2035-2065, or 2060-2090)
      6. Move the cursor over the graph, until you find the month with the highest projected temperature; read and record this value __________
   3. Next: consult a map to find a few cities south of your location; check climate information for those cities to find the city whose warmest month temperatures roughly match the temperature you recorded above.
      There is not a single “right” way to do this: you can start with a map (to find a few cities you may want to consider), then consulting any reasonable website (e.g., Wikipedia, NOAA National Weather Service, etc.) to find the data on average daily maximum temperatures in those cities.  You want to find a reasonably-close match with the warmest value you recorded (in step 4-vi).  There are a limited number of cities from which to choose, so an exact match is unlikely but also unnecessary.
      Record this city name here _____________.  This is your Comparison City 1.
   4. Then repeat step c, and find at least one additional city; record that name here __________. This is your Comparison City 2.
      You will want to assess your trees’ suitability using data from at least two cities (using additional cities is fine as well)
   5. You have three options to assess whether your tree species (from step a.) are likely to survive in the Comparison Cities: using the CalPoly Urban Tree Inventories, calling a tree manager in each of your Comparison Cities, or using the lists on this website.
      1. First, check the Cal Poly UFEI website Urban Tree Inventory: https://ufei.calpoly.edu/ If your Comparison City/cities tree inventory is present in the dataset (click on “Place” then enter the city name into the box), simply search for your trees of concern in each Comparison City (click on “Species,” then search). This is the recommended method.
      2. Second, if your Comparison City is NOT found in the Cal Poly dataset but is one of the 16 cities covered in our study, you can consult the tree lists on this website. You should then follow up with step iii (next).
      3. Call or email an urban tree manager (city arborist, consulting arborist, a tree non-profit) in your Comparison City.  Explain what you are trying to do, and then either discuss each tree of concern, or simply email them the list below.

5. Please report any ambiguities, errors or omissions to ilacan@ucanr.edu

6. Thank you, and best of luck with your trees! Last update: April 2023

Table to record the trees of interest and your consultations with the lists on this website, or the inventories on the Cal Poly UFEI website, or the phone call with tree managers in the Comparison City 1 and 2.  Note the name of comparison cities, and any information you obtained (e.g., “requires irrigation” or “only for parks, not for sidewalks” etc.)