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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Study says homes with big trees experience less crime than others

Jeff Barnard Associated Press

GRANTS PASS, Ore. – The U.S. Forest Service has found a new branch of crime-fighting.

A study by the agency found less crime occurs in neighborhoods with big trees in the yards and on the streets, and more crime at homes with smaller trees.

Researchers from the Pacific Northwest Research Station took crime data from the Portland Police Bureau and compared it to information from Google and onsite visits showing neighborhoods’ tree coverage.

Forest economist Geoffrey Donovan said large trees may be a signal to crooks that a neighborhood is well cared for, making it more likely criminals will be caught if they commit a crime. He added that small trees may aid criminals by providing hiding places and obstructing views.

Researchers looked at an area with 2,813 single-family homes where 394 property crimes and 37 violent crimes occurred from 2005 to 2007. They used images from Google Earth to measure the canopy of the trees at each house, and visited each house to measure the height and numbers of trees.

“This isn’t just a correlation of nice neighborhoods have nice trees,” Donovan said. “We controlled for two dozen other variables – whether a house had a burglar alarm, the condition of the house, fences and so forth, whether there were street lights outside the house, whether there was evidence they had a dog.”

“If a house had no trees, but window bars, a burglar alarm and street lights, you would probably experience less crime,” he added. “But all else equal, a house with less trees would have more crime than a house with more trees. Both number and size is what we recorded.”

The tipping point came when trees reached 42 feet tall, Donovan said. Looking closer, researchers found that those trees had canopies starting 9 feet off the ground, the same height as the top of first-story windows on most homes.

The height determined whether a tree obstructs the view from inside a house.

Donovan said the study is far from frivolous, and can help cities make decisions about their trees.

“Urban forestry is just one of the things local government can spend its money on,” he said. “The problem is we don’t fully understand those benefits. This would help us understand those benefits. The better we understand the benefits of things we spend money on, the more effective the things we spend money on.”

The study will appear in the journal Environment and Behavior.