The effect of trees on crime in Portland, Oregon

Studies looking at the effect of trees on crime have shown mixed results with some suggesting that the presence of vegetation can increase the fear of crime and others showing that it can reduce the fear of crime or crime itself. This research builds on earlier work by studying different kinds of crime around single-family houses and considering different kinds of vegetation separately in Portland, OR. Crime data were collected from the Portland Police Bureau. Tree crown data were determined from aerial imagery and confirmed through site visits. At site visits, other data known to be related to crime were collected, e.g., presence of a dog, neighborhood watch sticker, house condition, fencing. The effect of trees was mixed. Small trees on the property were associated with higher levels of crime, whereas street trees and larger lot trees were correlated with reductions in crime. The authors hypothesize that the smaller trees may reduce visibility, thus making it easier for criminals to escape detection, while the larger trees signal that a house and neighborhood are better cared for.