Every other Friday on Morning Edition NHPR’s Sam Evans-Brown tracks down answers to questions about the environment and outdoors for our listeners in a segment we call “Ask Sam."
An anonymous listener in Vermont asks: “I walk everyday and there are lots of trees in Vermont and I’m a tree hugger and I mean literally a tree hugger. And so I hug them and I always feel a sense of calm and I’m wondering if there’s anything that makes that happen? Do the trees notice when I hug them?”
The first part of the question I think is fairly easy. Why might you feel calm while hugging a tree? It is likely for some of the same reasons that going outside generally make us feel calm. At this point there are heaps of studies about the mental benefits of being outside. A hypothesis for why that might be that has come into vogue in recent years is that attention is a limited resource and we’ve only got so much of it to expend each day.
So being outside means “your attention is able to drift much more naturally, in a much more relaxed way from moment to moment,” explains science journalist Ferris Jabr. “You might be looking at the surface of a lake, watching the ripples, the leaves are falling from a tree, a bird flies by — and that can replenish our mental resources.”
But on to the second part of the question, which is the real reason I reached out to Jabr.
This question came shortly after he wrote a feature-length article for the New York Times Magazine about the research of Dr. Suzanne Simard. You may have heard of her work because she discovered something that pop culturally we have come to call the Wood Wide Web. This is the idea that trees in forests share nutrients, water, even carbon — the physical, chemical building blocks of trees — between each other, through a symbiotic underground fungal network.
However, in Jabr’s profile, there’s a moment in which he and Doctor Simard are walking through a forest and she says, “I’m really interested in whether they perceive us.”
If your first response is to snort that this is new-age nonsense, that’s because you haven’t been keeping up in the latest in botany.
“In fact there is research showing that trees and other plants can pick up on things like the wing-beats of a visiting insect. Some flowering plants will sweeten their nectar when they pick up on the wing-beats of a bee,” Jabr told me. “There are some studies showing that the roots of plants can pick up on the sound of running water and will grow towards that sound.”
One of the more famous examples of this is the ways that trees defend themselves from insect attacks. When pests like caterpillars start munching on the leaves of a tree, there are now dozens of studies that have confirmed that nearby trees will start to ramp up their production of chemicals that defend them against insects. It’s thought that they are somehow perceiving the volatile compounds that the chewed up leaves release into the air.
There is also fairly robust evidence that plant cells can perceive and respond to pressure waves, like the kind that are generated by sound in the environment and touch — like, say someone walking up to a tree and hugging it.
I don’t know for sure if that tree knows you’re hugging it. The careful way of putting this is that it’s a very reasonable hypothesis that someone could test. We also could answer the question: “So for sure, you like hugging trees, but do the trees like being hugged?”
Sam Evans-Brown, is host of NHPR’s Outside/In which you can subscribe to wherever you get your podcasts. If you’d like to submit a question you can record it as a voice memo on your smartphone and send it to firstname.lastname@example.org, OR call the hotline, 1-844-GO-OTTER, OR submit it here.