Social Life Under Cover: Tree Canopy and Social Capital in Baltimore, Maryland

By Meghan T. Holtan, Susan L. Dieterlen, and William C. Sullivan

Baltimore, MD (January 27, 2014) – To what extent does the density of the tree cover in a city relate to the amount of social capital among neighbors?  A lot, it turns out.

Baltimore New Broadway park 4The relationships between several variables investigated suggest a complex interaction between social capital and the environment. In spite of this complexity, findings suggest that more street trees should be planted in neighborhood public spaces.

Researchers at the State University of New York linked social survey data (N = 361) from the Baltimore Ecosystem Study, a long-term study of human and  urban environment interactions, with data from three urban markers. These included socioeconomic data, urban form (the spaces, places, and boundaries that define city life), and green space data at the census block group level using a geographic information system.

As expected, researchers found that tree canopy was significantly and positively correlated with social capital. When accounting for possible confounding variables like socioeconomic status and urban form, neighborhood tree canopy cover explained an additional 1.5% of the variation in an individual’s social capital, an increase of 22.72%.

In the study, published in Environment and Behavior, researchers identified statistical relationships between green space characteristics, including neighborhood tree canopy, and an individual’s social capital, or the value inherent in neighborhood social connections.

The results show a systematically positive relationship between the density of urban tree canopy at the neighborhood block group level and the amount of social capital at the individual level (r = .241, p < .01). The mechanism by which tree canopy facilitates increased levels of social capital is likely through driving increased use of sidewalks and outdoor spaces with trees.

There are few drawbacks to planting trees in response to the desire for increased neighborhood interactions. Trees are a relatively simple and affordable public works intervention, provide the quickest access to the restorative benefits of green space needed by busy people, and have multiple additional human health and environmental benefits. Researchers and design professionals should continue to include neighborhood tree canopy in the network of green space that supports the social benefits of urban ecosystems.

This research adds a new variable–neighborhood tree canopy–to the typologies of green space that affect human social connection. Trees are a relatively inexpensive and easy intervention to enhance the strength of social ties among neighbors.

Source: Social Life Under Cover,” Environment and Behavior (January 27, 2014)