What is a tree worth?

Hutchinson-Trees-690

Our thanks to Perle Besserman, who alerted us to “How Trees Calm Us Down,” a New Yorker article by Alex Hutchinson. Here is how the article begins:

In 1984, a researcher named Roger Ulrich noticed a curious pattern among patients who were recovering from gallbladder surgery at a suburban hospital in Pennsylvania. Those who had been given rooms overlooking a small stand of deciduous trees were being discharged almost a day sooner, on average, than those in otherwise identical rooms whose windows faced a wall. The results seemed at once obvious—of course a leafy tableau is more therapeutic than a drab brick wall—and puzzling. Whatever curative property the trees possessed, how were they casting it through a pane of glass?

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.

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