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Can a Tree Make You Happy?

Green spaces aren't just an aesthetic part of urban environments. They can play a role in human health, as well.
Q&A with social scientist Kathleen Wolf

Kathleen Wolf, a social scientist at both the University of Washington’s School of Forest Resources and at the U.S. Forest Service, studies how trees and green spaces can make urban dwellers healthier and happier. Wolf is working on a certification system for the outdoor built environment (similar to the U.S. Building Council’s Leadership in Energy and Environmental Design, or LEED, certification) and on a website that will aggregate more than 40 years of research about the effects of metropolitan nature on people.

Can you talk about the Sustainable Sites Initiative, or SITES, certification system and your role in putting it together?

I was part of a technical team that brought human health and well-being into the question of how to design outdoor built environments to optimize the benefits people gain from being in nature in cities. We worked from research that shows people heal faster when they have visual contact with nature, and that social cohesion is more likely if you have quality outdoor spaces where people can congregate. Studies show that people are more productive in the office if they have a view of green; so we considered how to optimize visual contact with green from everyone’s workspace within a business. And we attempted to put metrics on that.

How can you measure how happy a tree makes someone feel? And how do you optimize that in the form of a certification?

Kathleen WolfYou can do it in a variety of ways. First, by attaching physiological measurement devices, such as blood-pressure or heart-rate monitors. You can do it by self-report: As people enter and leave green spaces, you can ask them how they feel and measure their responses to certain things.  And then there's a second tier: So someone has spent a great half hour in this space; what are the consequences for their work, their studies, the behavior in their households? If you're more calm and connected to people who are also experiencing this space, might that have some consequences for community dynamics and positive social capital? All of those things are measurable, and based on that data, you can recommend the amount of time and type of activity or experience that people should have.

An example of this -- it’s called "Park Prescriptions" -- is starting to emerge in places like San Francisco, Albuquerque, and Chicago. If we understand that being in these green spaces involves activity, and the activity leads to reduced weight, which then leads to reduced chronic diseases, such as diabetes and heart disease, then doctors could prescribe that you spend so much time per day or per week on certain outdoor activities in these types of spaces. You can also describe the attributes of the places that people should spend time in. Studies reveal that certain characteristics of spaces lead to more positive experiences. One, for instance, is large trees. Another is that you don't want huge open spaces. For restorative experiences, it seems that more enclosed spaces -- think of them as outdoor rooms -- provide greater benefit.

How do you take into account a project's location within the community?

SITES acknowledges the connectivity of landscape, recreation systems, and transit. It acknowledges social connection, a sense of community, and bringing people into the site and welcoming them. It encourages the redevelopment of existing sites, rather than the continued pressing out to green fields at the city’s edge.

Describe Green Cities: Good Health, the U.S. Forest Service–funded project that will aggregate more than 40 years of science documenting the intersection of urban green spaces and community wellness.

We wanted to collect information about the social and economic benefits of trees and urban greening and present it in a public way. The website Green Cities: Good Health is the result. I did a rapid assessment of academic articles spread across disciplines like sociology, psychology, landscape architecture, and urban planning, and our team is writing up summaries along each of those themes. We have everything from healing, to work productivity, to school performance. We’re starting to see studies that demonstrate that kids who have green in their campus environment do better at standardized testing.

What message would you ultimately like to get across?

So often we run into this idea that plants in cities are about beautification or that green is an aesthetic amenity. What we've seen in this research is that, yes, it is an amenity, but it's also profoundly important for the health and functioning of people. We want to share those messages in a way that pushes urban greening beyond just things that look nice in our cities.

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Ashley Braun is a Seattle-based writer specializing in environmental news, food politics, and science. She currently covers U.S. climate politics at and previously worked as a writer and social media coordinator at Browse he... READ MORE >