Utopia may look something like the Emerald City if we take a recent study by Camilo Ordóñez and colleagues and really run with it. The researchers set out to understand how Toronto residents’ satisfaction with urban trees and tree management is influenced by factors such as canopy cover and visual greenness. Amid a push from many world cities to increase the number of urban trees, the results might come as a surprise: our delight in urban trees increases at larger neighbourhood scales and is more dependent on canopy cover and visual greenness than previously thought.
Think about walking through your neighbourhood. You’re not just looking at trees from a birds-eye perspective, like how tree canopy cover is typically measured. Instead, you’re experiencing them through what Ordóñez and his team term the “Viewshed Greenness Visibility Index (VGVI),” a measure that better represents the trees you would encounter during your daily strolls. The researchers found that satisfaction with urban trees was more closely linked to VGVI than tree canopy cover, suggesting that it’s not only about the number of trees but also how visible they are in our everyday lives.
Interestingly, the larger the neighbourhood scale, the stronger the association between our satisfaction and the tree visibility was. This could be because, at larger scales, residents might interact more with trees during their daily activities, deepening their experience and satisfaction.
However, the study highlighted an interesting disconnection. The researchers found no correlation between these measures of greenery and people’s satisfaction with urban tree management. It appears that how we perceive local government decisions about urban trees might be influenced by more than just our daily experiences with trees. It’s likely a more complex balance of social, community, and governance dynamics.
Urban trees serve an essential role in maintaining the health of our city environment. Not only do they enhance the aesthetics of urban landscapes, but they also provide critical ecosystem services, like air purification, noise control, and heat mitigation. Yet, despite their numerous benefits, urban trees are under threat due to urban developments and climate change. Moreover, access to tree services is distributed unevenly, underscoring the importance of integrating public perspectives in urban forestry management to address these disparities.
Grappling with the complex web of factors that shape public perception, the researchers sought to understand how urban dwellers’ satisfaction correlates with the abundance and visibility of urban trees, particularly as they’re experienced at the neighbourhood level. This approach translates into asking relevant questions. Is a neighbourhood draped in a thick canopy of lush trees more pleasing to residents? Or do residents find a few trees scattered across their daily walk routes more satisfying? Can assessing residents’ satisfaction with urban trees and their management lead to any improvements in urban tree strategy? The hope is that addressing these questions could lead to better-informed urban tree management decisions that directly impact the quality of city life.
The team designed a survey for the residents of Toronto. The survey was then rolled out across the city, capturing diverse experiences and perspectives of residents regarding urban trees’ abundance in their neighbourhoods and management by authorities. The team also collected data about respondents’ level of nature connectedness, tree knowledge, and various demographic variables, ensuring a rich, multifaceted dataset for the study.
This crucial data was married with objective measures of greenness—the Normalized Difference Vegetation Index (NDVI), per cent tree canopy cover, and the Viewshed Greenness Visibility Index (VGVI). The team used satellite imagery and land cover data from the City of Toronto to calculate these measures at three neighbourhood distances. The distances selected were assumed to represent areas that residents would walk through during their day-to-day activities.
A critical difference between the NDVI and the VGVI is that NDVI is just a measure of vegetation. Trees could boost it, but it could also be high when there are few trees and banks of stinging nettles. It’s the VGVI that gives a better measure of the impact of trees. In their article, Ordóñez and colleagues write:
While many studies rely on canopy cover to represent urban forest presence, our results suggest that this measure does not adequately capture how people are experiencing urban trees. Particularly in urban environments with a varying density of buildings that may block views of trees, canopy cover may overestimate how people’s ability to see trees in their neighbourhood. The eye-level tree visibility analysis using VGVI might better capture what people see in their neighbourhood, therefore being more reflective of their experiences with trees that shape perceptions like satisfaction.Ordóñez et al. 2023
So for true satisfaction, it’s not whether a city is green, but whether it can be seen to be green, that matters.
READ THE ARTICLE
Ordóñez, C., Labib, S.M., Chung, L. and Conway, T.M. (2023) “Satisfaction with urban trees associates with tree canopy cover and tree visibility around the home,” npj Urban Sustainability, 3(1). Available at: https://doi.org/10.1038/s42949-023-00119-8.
Cover image: Trees in a Toronto Winter. Image: Canva.