In cities across the United States, about 15 percent of land is considered vacant or abandoned. These areas can foster criminal activity, and urban residents, especially those in low-income neighborhoods, often view vacant land as a threat to their health and safety. A new study from the University of Pennsylvania , Columbia University, the University of California, Los Angeles, Rutgers University, and the U.S. Forest Service found that remediating these spaces can have a dramatic effect on both the perceptions of crime and vandalism and on the acts themselves.
The findings, published in the Proceedings of the National Academy of Sciences , revealed that neighborhoods where vacant lots were cleaned up experienced a 29 percent reduction in gun violence, 22 percent decrease in burglaries, and 30 percent drop in nuisances like noise complaints, public drunkenness, and illegal dumping.
Residents living near those same spaces also reported feeling much safer post-remediation, with 58 percent having fewer security concerns when leaving their homes and more than three-quarters saying they significantly increased use of their outside spaces for relaxing and socializing.
"Our analyses showed a substantial reduction in crime," says Penn criminologist John MacDonald , senior paper author, "particularly, a large reduction in gun assaults in neighborhoods that were in the lower 50 percent of income distribution in Philadelphia."
In addition, says Columbia epidemiologist Charles Branas , the lead author, the results show that greening blighted land "represents a pragmatic upstream infrastructural investment strategy to address complex social issues in cities. We found that police reports accurately reflected residents’ perceptions and revealed significant reductions in overall crime, gun violence, and nuisances."
The study, conducted in Philadelphia, is believed to be the first randomized controlled trial of its type.
To analyze the relationship between restoring vacant plots and crime in the city, the researchers randomly selected 541 vacant lots and then randomly assigned each to receive extensive, minimal, or no restoration: 201 were fully remediated, 174 received basic interventions like trash clean up and some weeding, and 166 were left alone, acting as the control. At the experiment’s end, every plot received the full treatment, which included removing trash and debris, grading the land, planting new grass via a rapid hydroseeding method, and maintaining the lot throughout the post-intervention period. á
Through police reports filed the 18 months leading to and following the restoration, the researchers then looked at applicable crime data. To understand what residents were experiencing and the effect of the restorations on these places, the team conducted repeated interviews with 445 randomly sampled residents living near the lots and also placed anthropologists in two neighborhoods.
"There is a lot of descriptive and theoretical research in criminology suggesting you can substantially affect crime by changing conditions of the built environment and making places less attractive to crime," MacDonald says. "But we have very few scientific studies that have experiments on a scale like this."
The results hold promise that quick, inexpensive restoration tactics such as the one MacDonald and colleagues employed can substantially improve neighborhoods. This strategy, chosen specifically to improveálocal neighborhood conditions block by block, yields a high return on investment and doesn’t displace long-term residents, like some other costlier methods unintentionally do.
It also has the potential to improve the health and well-being of the people in these places, says Eugenia South , an emergency-medicine physician at Penn Medicine.
"Feeling unsafe when you leave your home contributes to the experience of chronic stress in low-resource neighborhoods, which ultimately contributes to poor health and persistent health disparities," she says. "The fact that participants felt safer after cleaning and greening of vacant lots is an important and exciting result of this trial and demonstrates the wide-ranging impact this simple intervention could have on community health."
The intervention, MacDonald adds, could be scalable across the United States.
"What we’re seeing in Philadelphia is just a microcosm of what you see in legacy cities around the country, from Milwaukee to Youngtown, Ohio, to Scranton, former industrial cities with a lot of vacant land in need of remediation," he says. "This suggests that one additional benefit of improving land could be to reduce crime."á
Future work includes conducting a longer-term data analysis of the vacant lot cleanup and running a similar trial that focuses on bringing vacant houses to code.
The study was funded by the National Institutes of Health (Grant R01DA037820) and the Centers for Disease Control and Prevention (Grant R49CE002474). Researchers include Penn’s John MacDonald, professor of criminology and sociology in the School of Arts and Sciences ; Eugenia South, assistant professor of emergency medicine in the Perelman School of Medicine ; Douglas Wiebe , associate professor of biostatistics and epidemiology in Perelman; Charles Branas, chair and professor of epidemiology, Columbia University’s Mailman School of Public Health; Philippe Bourgois, professor-in-residence, University of California, Los Angeles; Michelle Kondo, research social scientist, U.S. Forest Service; and Bernadette Hohl, assistant professor, Rutgers University School of Public Health.