Did community greening reduce crime? Evidence from New Haven, CT, 1996-2007

For some volunteers, neighborhood safety is one of the reasons for becoming involved in community greening. For example, many volunteers of the Community Greenspace program at the Urban Resources Initiative in New Haven, Connecticut believe that there is a potential reduction in crime from community greening activities, even though it is not an explicit goal of the program. These types of community-led interventions are distinct from both existing tree canopy and large-scale municipally led initiatives. These types of interventions remain understudied with respect to the potential for reducing crime. We therefore used a quasi-experimental difference-in-differences (DID) approach to test whether more than a decade of street tree planting (1996-2007) in New Haven had an effect on crime levels at planting sites (n = 300) compared to control sites that received no Community Greenspace-planted trees (n = 893). We examined violent, property, and misdemeanor crimes (comprised of vandalism, prostitution, and narcotics crimes) individually and jointly to test for crime-type specific effects, while controlling for sociodemographic factors and spatio-temporal trends. In general, we found a null relationship between trees planted and crime on block faces per year at the p < 0.05 level. Increases in crime were not observed on treatment sites. We discuss implications for tree inventories and monitoring, study design, and techniques to assess impacts of tree planting efforts.