By Canopy Team on September 9, 2019
Megan Wheeler is a PhD candidate at Arizona State University and over the summer she worked with San Francisco Estuary Institute (SFEI) and Canopy to analyze data on Palo Alto’s tree removal permits. The information gleaned from Megan’s report will be used to guide Canopy’s work in the future. We asked Megan some questions about her research to better understand her methods and findings.
Megan: I grew up in the San Diego area, but am currently working on a PhD at Arizona State University in Phoenix, AZ. My work there focuses on urban ecology, and I’m particularly interested in how and why people manage and change their yards to get the things they want, which can have important implications both for people and for the environment.
Megan: I came to work with SFEI and Canopy this summer through a new National Science Foundation funding program supporting non-academic research internships for graduate students. I had previously met Robin Grossinger, the SFEI Resilient Landscapes program co-director, at a conference and learned about the urban ecology work going on at SFEI, and so on seeing this opportunity I got in touch. Once I heard about the possibility of thinking about motivations for tree removal with Canopy, it was set—the project fits perfectly into my dissertation work, and I was excited to get started!
Megan: The goal of my project was to understand why Palo Alto residents remove protected trees—coast redwoods, valley oaks, and coast live oaks over a certain size. I reviewed arborist reports submitted with tree removal permit applications between 2000 and 2018 and used thematic coding to understand the different reasons why people needed to remove these trees.
The process of thematic coding involves reading through documents, in this case the arborist reports, and noting each instance of a particular theme or idea. For example, trees were often removed if they were dead or dying, so I noted every time an arborist report recorded that a tree had evidence of decay, was infested with pests, had a declining crown density, or appeared to have a particular disease.
From the whole set of applications, we can learn about the most common reasons for tree removal and think about how we can continue to protect trees and promote their inclusion in cities while also accommodating the need to remove unhealthy or hazardous individuals.
Megan: One of the interesting things I learned was that the protected native oak trees are often removed for health reasons, as they show signs of disease, decay, or crown dieback. However, they usually aren’t very large or old, which makes their poor health somewhat surprising.
An important next step will be to understand why oaks might not be doing so well in residential spaces—maybe they get too much water from surrounding irrigation or their root systems don’t have enough space. This would help us think about making recommendations to tree caretakers about the most important things to do to keep their oaks healthy.
Megan: Gathering all of the documents together and getting them into the right format was surprisingly hard! The coding software I used needs to be able to recognize individual words in a document, but the permit applications were all scanned PDFs. There was a lengthy process of converting PDFs into Word documents before I could even get started with the thematic coding.
Megan: My findings show that most people remove protected trees when they become hazardous or are in declining health, rather than during construction projects. Given this result, I think important next steps are to consider how we can help trees stay healthy and how we can plant strategically to reduce future hazards.
Big trees inevitably present some risks, but can also be a beautiful, defining feature of a yard or neighborhood and can provide benefits like cooling shade and homes for birds and other wildlife. Understanding how to steward these trees for as long as possible and as safely as possible is an important goal, and it’s been great to work with Canopy to make a little bit of progress towards that goal.
Megan: Palo verde—the trunks are green! Plus they have beautiful yellow flowers in the spring and are visited by tons of bees.
Stay tuned for more information on Megan’s final report. Contact Elise Willis, Community Forestry Program Manager, at [email protected] for any questions about this project. This project is in partnership with with San Francisco Estuary Institute (SFEI) and partially funded by the National Science Foundation.