A 10-year effort to reclaim vacant lots in Philadelphia yields positive results

We all know about modern theories of policing that suggests signs of deterioration in a community – vacant lots, boarded-up buildings and, most famously, broken windows – communicate to would-be criminals, “No one cares about this place, so you don’t have to either.” A related theory suggests that the presence of all these same “physical incivilities” promotes weak social ties among residents, increasing crime and discouraging the kind of community self-policing that Jane Jacobs celebrated.

These theories seem sensible. You’re more likely to drop a candy wrapper on a sidewalk that’s already covered in trash. But there hasn’t been a lot of quality, hard data to back this up.

A new study, published online this week in the American Journal of Epidemiology, offers some of the more promising evidence. Researchers at the University of Pennsylvania studied a 10-year project in Philadelphia to convert vacant lots into park space. They found that gun-related assaults significantly declined in areas around the lots that had been greened. Vandalism and criminal mischief also significantly fell off.

Residents in some areas around these newly converted green spaces also reported feeling less stress and getting more exercise – presumably some of the byproducts of a neighborhood reclaiming its streets from crime.

The researchers, led by associate professor of epidemiology Charles C. Branas, conclude:

With respect to safety, both the broken windows and incivilities theories support our findings, and we can speculate that violent crime may have simply been discouraged in the presence of greened and tended vacant lots which signaled that someone in the community cared and was potentially watching over the space in question... However, the impact of greening may have also been more tangible, especially for gun assaults, where it could be speculated that vacant lots may be a haven, storage ground, or disposal point for illegal guns.

The researchers were studying a project launched in 1999 by the Pennsylvania Horticultural Society, which cleared debris and planted grass and trees on 4,436 lots, covering 7.8 million square feet of new green space, over the course of a decade in Philadelphia. Each lot was also surrounded with a low fence – just enough to communicate to passerby that the land was cared for.

In comparing these makeshift parks to a control group of vacant lots culled from the city’s database of more than 50,000 abandoned properties, the researchers did make one surprisingly discovery. Cases of disorderly conduct actually increased around the greened lots. This may, however, be a positive sign that communities are now gathering in these places (and having a disorderly good time) or that, feeling more protective of them, residents are more likely to call the police.

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