Tuesday, November 02, 2010

Could birdscaping attract or deter criminals?

A study about the effect of urban trees on crime rates poses the possibility that trees can reduce the incidence of certain crimes. Covering a three-year period, researchers looked at 431 crimes reported among a sample of 2,813 single-family homes in Portland, Ore.

The abstract for the study's article in Environment & Behavior says:
In general, the authors find that trees in the public right of way are associated with lower crime rates. The relationship between crime and trees on a house’s lot is mixed. Smaller, view-obstructing trees are associated with increased crime, whereas larger trees are associated with reduced crime.
Geoffrey Donovan of the U.S. Forest Service's Pacific Northwest Research Station and Jeffrey Prestemon with the Southern Research Station obtained crime data from the Portland Police Bureau from 2005 to 2007 and grouped the incidents into seven categories. They examined only crimes for which a physical address was given and paired this information: 394 property and 37 violent crimes.

The researchers examined the relationships among crime and more than two dozen variables they compiled, including the number and size of trees on a lot and the size of trees on surrounding areas. Large trees were associated with a reduction in crime, while numerous small trees were associated with an increase.


“We believe that large street trees can reduce crime by signaling to a potential criminal that a neighborhood is better cared for and, therefore, a criminal is more likely to be caught,” Donovan said. “Large yard trees also were associated with lower crime rates, most likely because they are less view-obstructing than smaller trees.”

In contrast, their analysis suggested that small yard trees might actually increase crime by blocking views and providing cover for criminals—an effect that homeowners can mitigate by keeping trees pruned and carefully choosing the location of new trees.

Photo courtesy of Geoffrey Donovan/US Forest Service

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1 Comments:

Blogger Rick said...

Large trees are also correlated with relative wealth, which is correlated negatively with crime. So I suspect that these neighborhoods have large trees for the same reason they have lower crime rates--not that the large trees result in lower crime rates.

November 12, 2010 8:04 PM  

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