The Relationship Between City "Greenness" and Homicide in the US: Evidence Over a 30-Year Period

Residents in US cities are exposed to high levels of stress and violent crime. At the same time, a number of cities have put forward "greening" efforts which may promote nature's calming effects and reduce stressful stimuli. Previous research has shown that greening may lower aggressive behaviors and violent crime. In this study we examined, for the first time, the longitudinal effects over a 30-year period of average city greenness on homicide rates across 290 major cities in the US, using multilevel linear growth curve modeling. Overall, homicide rates in US cities decreased over this time-period (52.1-33.5 per 100,000 population) while the average greenness increased slightly (0.41-0.43 NDVI). Change in average city greenness was negatively associated with homicide, controlling for a range of variables (beta = -.30, p-value = .02). The results of this study suggest that efforts to increase urban greenness may have small but significant violence-reduction benefits.