Trees and Crime

A little while ago, we posted about a research project in Portland, Oregon that was developing heat island maps to identify and display trouble spots in the city. Now we have yet another piece of interesting research coming from Portland. A 2012 study conducted by Geoffrey H. Donovan and Jeffrey P. Prestemon examined whether the presence of trees on a house’s front lot has an effect on crime in the city.

Donovan and Prestemon used reports from the Portland Police Bureau from 2005 to 2007, looking at the occurrences of seven different types of crime. A total of 2813 family homes were studied, with 431 having experienced some sort of crime.

It was found that trees on the road allowance of a property are associated with a decrease in crime. Donovan and Prestemon suggest multiple possible explanations for this. For example trees can signal to criminals that a neighbourhood is well taken care of, so a criminal would be more likely to be caught.

It was also found that the further away a tree is from the house, the more likely it is to decrease crime. This is a point in favour of street trees, which are planted on the road allowance close to the sidewalk.

However, there was also some evidence to suggest that a greater number of smaller trees on a property increase crime. This could be because they provide cover for criminals and block neighbours’ views of the house. However, homeowners can alleviate this risk by keeping trees pruned and being careful about the location of trees.

Since this is an observational study, we can’t be sure that the trees were the cause of the crime occurrences. In addition, the correlations found were relatively small. However, it’s an interesting prospect, and worth looking at in Hamilton.

Check out the full study at http://eab.sagepub.com/content/33/3/343.short for more information!