When it comes to controlling crime, police tend to favor more policing, while social scientists see the symptom of deeper, social problems. Urban planners, on the other hand, focus on the trees.
There is a long-standing debate, apparently, over whether vegetation encourages or discourages crime. One school of thought holds that criminals will hide behind the bushes. A study of Philadelphia by researchers at Temple University situates itself squarely on the other side:
…this research provides strong evidence of the association between vegetation abundance and crime related to assaults, robberies, and burglaries. In Philadelphia, these crimes occur at higher rates in sparsely vegetated areas—a relationship that is not explained by poverty or the gradient between inner-city and more densely populated areas of the city.
In other words, the greener the neighborhood, the fewer the crimes (except for theft, which proved impervious to vegetation). But why? As Discover Magazine reports:
The explanation, the authors say, is twofold: One, green spaces encourage people to spend more time socially outdoors, which discourages crime. It’s especially helpful for crime control when young and old people mix together in public places. And two, the presence of plants has a therapeutic effect. Vegetation decreases mental fatigue and its associated symptoms, such as irritability and decreased impulse control, both considered to be precursors to violence.
The study has its limitations—it looked at only one year of crime data in Philadelphia, at a census tract level, using a very broad measure of vegetation—but it isn’t the only of its kind. A study six months earlier in the same journal found similar results, but in Baltimore.