From the Trust for Public Land - Lands & People Magazine - Fall 2004:

Excerpt from "Park Power!" by Paul M. Sherer

"...Residents of cities and towns across the country have learned that banding together to create a new park, garden, or playground can leave a community with a lot more than new swing sets, rows of vegetables and flowers, and green space. Neighbors become more willing to protect one another's families and properties from harm. They are more likely to accost or report teenagers spraying graffiti or harassing passersby and are more likely to mobilize to demand better schools and libraries.

To social scientists, what these residents are experiencing is the growth of "social capital" — the social ties, mutual trust, and standards of behavior that enable people to work together toward shared goals. Just as investment capital builds financial strength, social capital builds community strength. Researchers have found that, when compared to otherwise similar neighborhoods with weak social capital, neighborhoods with strong social capital enjoy fewer homicides and other violent crimes, fewer property crimes, reduced juvenile delinquency, better-performing governmental institutions, higher educational achievement, and lower rates of asthma and teen pregnancy. Where social capital is weak, neighborhoods fall into decline.

Some of the strongest evidence for the social benefits of parks comes from the Project on Human Development in Chicago Neighborhoods (PHDCN), a $50 million-plus interdisciplinary study on the roots of crime, substance abuse, and violence. The study is focused on a concept related to social capital called "collective efficacy"—social cohesion and trust among neighbors combined with their willingness to intervene for the common good. Collective efficacy can be built through activities such as working together on community gardens and holding community festivals in neighborhood parks.

As part of the study, researchers interviewed more than 8,000 residents of 343 Chicago neighborhoods. Questions were designed to measure collective efficacy, perceived levels of neighborhood violence, and actual violence experienced by an interviewee. Researchers also reviewed homicide reports for the neighborhoods. The project found that neighborhoods with higher collective efficacy experienced lower rates of crime and juvenile delinquency.

Simply having a park where neighbors can interact can increase social capital, says Professor Robert J. Sampson of Harvard University's Department of Sociology, a lead researcher on the Chicago study. "It's hard to develop trust and cohesion where you can't see people or interact with them," Sampson notes. And while isolation breeds cynicism and fear, neighborhoods with greater interaction enjoy "lower crime rates and a sense of social cohesion."