In Urban Neighborhoods, More Trees Equals Less Crime

By Lisa Raffensperger | April 5, 2013 1:40 pm

Say you live down the street from a small urban park—does that make you feel more safe, or less? Green space has been thought to work both ways. Shrubs, for instance, could conceal burglars, or a tree-lined sidewalk could obstruct a clear view of the street. On the other hand, green space encourages people to spend more time in public areas, which deters crime—and greenness might even be good for the soul.

A new study finds that, in Philadelphia at least, greener neighborhoods have significantly fewer crimes than non-vegetated areas. And this effect held true even after the researchers controlled for socioeconomic factors.

The researchers began with crime data for 2005 across the city, broken down by neighborhood (each containing a few thousand people) and type of crime: assault, robbery, burglary or theft. (The authors chose not to include rape and murder because they are relatively rare.) They combined this data with images taken the same year by NASA’s Landsat satellite. The satellite carries a sensor which can detect chlorophyll remotely, from which the researchers calculated an average “greenness” of each neighborhood.

When the data were matched up, the researchers found that greenness was a strong marker of safety. Rates of assault, robbery and burglary were all significantly higher in non-vegetated neighborhoods. This effect remained true even when the effects of population density, poverty and education were taken into account, the authors report in Landscape and Urban Planning.

The explanation, the authors say, is twofold: One, green spaces encourage people to spend more time socially outdoors, which discourages crime. It’s especially helpful for crime control when young and old people mix together in public places. And two, the presence of plants has a therapeutic effect. Vegetation decreases mental fatigue and its associated symptoms, such as irritability and decreased impulse control, both considered to be precursors to violence.

This “plant therapy” mechanism is bolstered by the Philadelphia findings. The most violent of the crimes studied, aggravated assault, was most strongly correlated with a neighborhood’s degree of greenness, while the least violent crime, theft, showed no association. This could indicate that it’s a violent mentality itself that green spaces are discouraging.

That hypothesis needs further study. This project didn’t differentiate between well-kept green areas and overgrown vacant lots, for example, which would likely have different effects on crime. And it only looked at one year in one American city. However it’s something for city planners to consider—and perhaps, in their zeal to make cities safe, to plant a tree.

Image courtesy Mihai Bojin / Flickr

CATEGORIZED UNDER: Environment, top posts
  • JonFrum

    “That hypothesis needs further study”

    Ya think? Repeat after me: correlation is not causation, correlation is not causation, correlation is not causation.

    “The explanation, the authors say, is twofold…”

    The explanation, the authors speculate, is twofold…

    There, fixed.

    • http://www.facebook.com/profile.php?id=1096206214 Aidan Skillings

      Correlation may not be causation but this is a pretty significant correlation. It would be unlikely if this was mere coincidence. Still, it would be wise to do the study on a much larger scale -other nations in particular- to see if the findings are consistent throughout.

  • de Broglie

    Green areas have higher property values and more affluent residents.

    • Kevin S.

      That’s what I was thinking. It looks like they didn’t control for socioeconomic status.

      • Thread Untangler

        “And this effect held true even after the researchers controlled for socioeconomic factors.”

  • http://new-movies-online.blogspot.com/ kyra bank

    10 box office 2013
    2013boxofficemovies.blogspot.com

  • Patriot

    That’s just a false assumption. The only certainty is More Guns in Law Abiding Citizens possession = Less Crime. FACT.
    What Trees have to do with it is beyond Me.

    • JWrenn

      Yup the wild west had no crime…oh wait.

    • http://profiles.google.com/hypatia08 Hypatia Hypatia

      You get A+ for quoting the NRA’s Bible textually.

  • Katie

    Much of this can probably be connected to Broken Windows Theory. If an area appears to be well cared for there will be less crime. Run down areas invite potential offenders who view the area as uncared for and an easy target. Such areas also have an increased fear of crime. I would imagine having more green space would give the impression of a vibrant area when matched with a well cared for area. The fact that they did not look at overgrown vacant lots versus well kept areas says it all. One year in one American city with poor methodology is not a news story. Replicate!!

  • http://www.facebook.com/InklingBooks Michael W. Perry

    Like others, I’m skeptical there’s a direct cause-effect relationship here. Controlling for the numeric factors social scientists like (such as income), isn’t controlling for all the differences between people.

    Keep in mind that people make choices about where they live. Some like to live around greenery, with parks, tree-lined streets and even small wooded areas. Others either don’t like such areas or don’t value them much. And it’s the latter that, I suspect, might tilt toward crime. If you like being angry and violent, you don’t want greenery calming you down.

    • rednip

      Your theory still makes the claim that ‘greenery’ is primary cause for the change. However, in your estimation additional new green space will only have a positive effect when the thugs look around their new brighter neighborhood with disgust and exclaim ‘I’m outta here!’.

  • http://www.facebook.com/people/Chunkie-Jones/100001932013087 Chunkie Jones

    Black people don’t plant trees.

    • SinclairZ

      Back people planted a whole lot of trees and plenty of other crops and all they got for it was the whip across their backs.

      • http://www.facebook.com/people/Chunkie-Jones/100001932013087 Chunkie Jones

        Blacks were brought here as slaves and because of this their descendents enjoy living in a developed nation. Where on Earth do Black people have a better standard of living than the USA? They got a lot more than a whip across their back. They got to enjoy living off of the largess of Western civilization.

        • http://www.facebook.com/profile.php?id=1096206214 Aidan Skillings

          ‘Canada’

          • http://www.facebook.com/people/Chunkie-Jones/100001932013087 Chunkie Jones

            You make an excellent point. Canada enjoys an excellent standard of living, largely due to the fact that they are not presently burdened by an enormous underclass, like we have in the USA. Of course you realize that Canada is more a mere economic satellite of the American empire and less a real country. Nonetheless, in Canada there too is a tiny black population living off of the accomplishments and hard work of White people.

        • http://profiles.google.com/hypatia08 Hypatia Hypatia

          Especially the slave women who got to enjoy the visits of the whiskey-swilling plantation owner who topped the evening’s entertainment by suggesting his friends put down their cigars and all “go down to the quarters”.

    • Marcus Harvey

      Back people planted a whole lot of trees and other crops and all they got for it was the whip across their backs.

  • thedude

    communites that are mindful of their enviroment are more likely to be mindful of the people within. Pretty easy to understand.

    • JonFrum

      That’s what is known as an assertion. I have no idea what ‘mindful of their environment’ means in this case. Are gentrifying white yuppies who organize park cleanup days more ‘mindful of people’ than black inner city residents who don’t?

      • nurture nature

        Yes, but not because of their race. This assertion is based on what’s known as “common sense”.

  • polistra24

    No good examining ‘static’ differences. You can’t possibly pry out one cause from all the other stuff.

    You could use ‘natural experiments’ to get meaningful data: Find cities that planted a bunch of full-grown trees with no other change, and find cities that removed a bunch of trees because of disease or insect damage. If crime changed in those neighborhoods after the addition or removal of trees, you could adduce causation.

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  • organicroseski2

    My comment might not have to do with this; but trees release oxygen while they are taking in carbon dioxide. Tree improve the air quality. Maybe, people think more clear in a tree area; therefore, less crime? I am really stretching it.

    • http://www.facebook.com/profile.php?id=1096206214 Aidan Skillings

      Air tends to balance itself pretty quickly so I don’t know about this one. But excessive car pollution might have some effect. I know it’s not good for health, but whether it alters your mindset is something none of us know, far as I’ve been informed.

      • organicroseski2

        If another reply comes thru–lst from iPhone– kept on buffering. Anyway, trees, settle, trap and hold particle pollutants. They absorb carbon dioxide (I believe other toxic gases too), and release oxygen. Particle pollutants that can harm lungs are trapped on the leaves and with rainwater, fall to the ground. Maybe it does alter the mindset, just feeling better might be the “plus.”

  • trpiclprincss13@gmail.com

    Every weekend of my childhood was spent in one or more of those parks. I shared that with my child. My grandfather taught us the names of different sizes of wood for fires, we tabogganned, we sledded, we went to plays and learned how to swim. Watched hundreds of Canadian geese squadron and fly.
    We rode our bikes and swung til dark. We grew many plots in community gardens as adults. Why would you take that away? Such a basic cultural requirement. Like a library built of slate in the cool mansion bequested for that purpose.

    • http://profiles.google.com/hypatia08 Hypatia Hypatia

      BEQUEATHED

  • armor bear

    it’s very comprehensive and exciting about Some kinds of crime ! it’s so helpful to me, and your weblog is very good. I am definitely going to share this URL with my friends. and says about don’t Crime like this type.

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