By Charles C. Branas, Rose A. Cheney, John M. MacDonald, Vicky W. Tam, Tara D. Jackson and Thomas R. Ten Have
Philadelphia, PA (November 11, 2011)- Headed by researchers at the University of Pennsylvania’s Perelman School of Medicine, A Difference-in-Differences Analysis of Health, Safety, and Greening Vacant Urban Space pieced together an interesting picture of how cities with greenspace can improve the health of its residents.
The authors conducted a decade-long difference-in-differences analysis of the impact of a vacant lot greening program in Philadelphia, Pennsylvania, on health and safety outcomes. “Before” and “after” outcome differences among treated vacant lots were compared with matched groups of control vacant lots that were eligible but did not receive treatment.
Across 4 sections of Philadelphia, 4,436 vacant lots totaling over 7.8 million square feet were greened from 1999 to 2008. Estimates showed that vacant lot greening was associated with consistent reductions in gun assaults across all 4 sections of the city and consistent reductions in vandalism in 1 section of the city. Regression-adjusted estimates also showed that vacant lot greening was associated with residents’ reporting less stress and more exercise in select sections of the city.
These findings suggests that once greened, vacant lots may reduce certain crimes and promote some aspects of health. Limitations of the current study are discussed. Community-based trials are warranted to further test these findings.