Trees on streets and boulevards reduce crime. Do we know the how or why of this particular correlation, nope. But we do know that trees on private lots also tend to reduce criminal activity, with the proviso that they are over 42 feet high. The studies linked are quite fascinating and most definitely worth a read.
But recent research suggests the opposite: trees don’t give burglars and highwaymen a place to hide, rather they may reduce crime in a neighbourhood.
One piece of research from 2001 focused on a public housing project in Chicago, where some buildings had trees out front, others did not. The research found that buildings with fewer trees or barren yards had more crime reports, while buildings with trees had fewer crimes. Because residents of the project were randomly assigned to various apartments, the differences in crime couldn’t be attributed to factors like income.
A more recently published article in the journal Landscape and Urban Planning focused on Cincinnati. The city’s trees were being killed by the Emerald Ash Borer beetle. Researchers took advantage of the spread of the beetle to study the relationship between trees and crime. They found that when a tree is killed and removed, crime in the area tends to go up.
bleatmop
Mystro
Dead Wild Roses 
8 comments
September 19, 2016 at 6:05 am
roughseasinthemed
Trees on streets or in gardens? Difference. We have trees in our streets in Gib (orange) and Spain (palm but used to be orange). But they are decorative.
Neighbours in Spain have trees in their gardens, short, usually lemons, but everyone has rejas – metal bars/grilles – over their windows. They deter crims too. We all also have locked gates.
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September 19, 2016 at 8:07 am
The Arbourist
@RSitM
The crime reducing effect for trees happens when there are trees in public boulevards and public thoroughfares.
With private dwellings the tree height makes the difference, 42 feet according to the study. :)
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September 19, 2016 at 10:22 am
roughseasinthemed
@Arb because I know you like me to type four extra characters … I did read the linkies. I got the bit about the houses with trees in gardens, that was nicely clear. The sort of general trees around reduces crime was less specific I thought. But I live in areas of low crime (touch wood) anyway but I doubt trees are the reason. More likely in Spain people still remember the civil war and chivatos everywhere, and in Gib, you either have to cross a frontier or escape by sea. Or escape by boat, to be more accurate.
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September 19, 2016 at 11:20 am
john zande
More proof ents are real!
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September 19, 2016 at 1:47 pm
The Arbourist
@RSitM
The studies were from NA, and the urbanscapes associated with them.
What struck me while reading the studies was the potential for confounding variables. The correlation seems to be there, but causation – as you mentioned – doesn’t seem quite as solid proposition. :)
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September 19, 2016 at 1:48 pm
The Arbourist
@JZ
And more weight to the general proposition that more trees are a good thing. :)
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September 19, 2016 at 4:34 pm
john zande
More magic trees, sure ;)
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September 19, 2016 at 8:39 pm
bleatmop
My suspicion is that this has more to do with the change in the socioeconomic makeup of a neighbourhood rather than the greenery itself. Green spaces take both time and money to build and maintain. Also, many things can change the makeup of a neighbourhood, such as the flight of those of a more affluent socioeconomic status for a variety of reason, including a disaster such as beatles destroying all the trees or poorer people moving in.
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