A new study published in the American Journal of Epidemiology analyzes a 10-year project in Philadelphia to turn abandoned lots into public parks. As it turns out, the project hasn’t just eliminated eyesores — it’s also reduced crime.

Gun-related assaults, vandalism ,and criminal mischief all dropped off significantly in the reclaimed spaces. The researchers theorize that this is because manicured parks suggest to would-be criminals that an area is being watched over by concerned citizens who might call the cops. Also, lawns aren't as good for storing guns and other contraband as lots overgrown with weeds and trash.

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.

Four thousand-plus lots might sound like a lot, but Philadelphia has at least 50,000 abandoned properties yet to go. Just imagine the effect on crime if we greened them all.

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