Analysis of Health, Safety, and Greening Vacant Urban Space


Philadelphia Horticultural Society

As many U.S. cities have de-industrialized, urban acres previously used for commerce or factories have been cleared and left as vacant, often rundown, lots. In recent years, however, some of these have been reclaimed as “green” or open space for public use. Groups in Philadelphia, for instance, consistently improved lots by “removing trash and debris, grading the land, planting grass and trees to create a park-like setting, and installing low wooden post-and-rail fences around each lot’s perimeter to show that the lot was cared for and deter illegal dumping,” as scholars from the University of Pennsylvania note in a 2011 study.

The study, published in the American Journal of Epidemiology, “A Difference-in-Differences Analysis of Health, Safety and Greening Vacant Urban Space,” focused on Philadelphia’s greening initiative from 1999 to 2008 to assess its impact on both personal and community well-being. The researchers compared information on more than 50,000 vacant city lots (approximately 10% greened and 90% not greened), and correlated this data with bi-annual community health surveys of some 5,000 city residents and police department crime statistics.

The study’s findings include the following:

  • Lots converted into green space throughout the city were strongly correlated with a lower rate of gun assaults during the study period.
  • Rates of vandalism and criminal mischief declined in one section of greened city lots studied.
  • “Vacant lot greening was associated with residents reporting significantly less stress and more exercise in select sections of Philadelphia.” The authors suggested that the new greened lots were seen as safe recreational spaces by residents, and social differences in each neighborhood may have impacted green space use.
  • However, instances of disorderly conduct actually increased on average. Illegal dumping increased in one area of lots studied.

The authors suggest that two social science theories may help explain how greening can positively impact a community:  “The ‘broken windows’ theory suggests that vacant lots offer refuge to criminal and other illegal activity and visibly symbolize that a neighborhood has deteriorated, that no one is in control, and that unsafe or criminal behavior is welcome to proceed with little if any supervision…. A related theory, the ‘incivilities’ theory, suggests that physical incivilities, such as abandoned vacant lots, promote weak social ties among residents and encourage crimes, ranging from harassment to homicide.” However, the researchers caution that their “knowledge of how exactly the greening of vacant lots works to change health and safety remains limited.”  Writer: