What Is a Tree Worth? – The New Yorker

September 15, 2015

What Is a #Tree Worth?
http://www.newyorker.com/tech/elements/what-is-a-tree-worth Study on Toronto shows 10 more trees/block =+1% in wellness =$10k/person =being 7yrs younger


“That is the riddle that underlies a new study in the journal Scientific Reports by a team of researchers in the United States, Canada, and Australia, led by the University of Chicago psychology professor Marc Berman. The study compares two large data sets from the city of Toronto, both gathered on a block-by-block level; the first measures the distribution of green space, as determined from satellite imagery and a comprehensive list of all five hundred and thirty thousand trees planted on public land, and the second measures health, as assessed by a detailed survey of ninety-four thousand respondents. After controlling for income, education, and age, Berman and his colleagues showed that an additional ten trees on a given block corresponded to a one-per-cent increase in how healthy nearby residents felt. “To get an equivalent increase with money, you’d have to give each household in that neighborhood ten thousand dollars—or make people seven years younger,” Berman told me.

You can produce an attenuated version of the same effect simply by looking out a window, or (for experimental convenience) at a picture of a nature scene. Over the past few years, Berman and his colleagues have zeroed in on the “low-level” visual characteristics that distinguish natural from built environments. To do this, they broke down images into their visual components: the proportion of straight to curved edges, the hue and saturation of the colors, the entropy (a statistical measure of randomness in pixel intensity), and so on. The view of an arboretum, for instance, tends to have higher color saturation than that of a street corner, indicating that “the colors in nature are more of the ‘purer’ version of those colors,” Berman said. Even when images are scrambled so that there are no recognizable features, like trees or skyscrapers, to betray what they represent, their low-level visual characteristics still predict how much people will like them.”