The Heartbeats and Songs of Trees

Biologist George David Haskell says that our unaided ears can hear how a maple tree “changes its voice as soft leaves of early spring change into the dying ones of autumn.”

I’m a tree hugger from way back; in fact, you could say I was hugging trees before tree hugging was cool. So when a book titled The Songs of Trees recently hit store shelves, I couldn’t help but notice. In it, author and biologist David George Haskell makes the case that trees are masters of connection and communication.

I know from firsthand experience, however, that anytime you mention or write that plants are sentient or that they have any sort of messaging system, you’ll get the kind of odd looks and outraged commenters that I do. But in recent years, biologists, ecologists, foresters, naturalists and researchers are increasingly proving that trees “speak” and—even, perhaps, more surprising—have a “heartbeat” much like ours.

Branches of the family

In his book, George David Haskell states that when most people look at a tree, it seems to appear as an individual, solitary plant. They have trouble perceiving trees as being interconnected, so they can’t comprehend that they communicate with each other.

A forester scraped away the surface of a 400-year-old stump and found that it was still green with chlorophyll. The surrounding beeches were keeping it alive.

But some people do hear trees talk. Haskell uses the example of the Waorani, who live in the Amazon rain forest in Ecuador. For them, the notion that all living things communicate seems obvious, and it’s reflected in their language. Anthropologists trying to translate Waorani words into English struggle because there are no terms for tree species: one ceibo tree could be “the ivy-wrapped tree” and another might be “the mossy tree with black mushrooms.” In the Waorani culture, it’s taken for granted that harming a tree could cause trouble for humans or that a tree might scream when cut.

A German forester, Peter Wohlleben, came to a realization that’s similar to Haskell’s, which he outlined in his 2016 book, The Hidden Life of Trees. He found evidence that trees had complex social lives after he came across a leafless, old stump that was still alive after 400 to 500 years. Since every living being needs nutrition, the only explanation he could come up with was that the stump was still being supported by a sugar solution that neighboring trees had to be providing via roots. His forestry education had taught him that trees are competitors that struggle against each other for light and space, but the living stump was proving the opposite. The trees were very interested in keeping every member of that community alive. He believes that they, like us, have family ties in addition to relationships with other species.

Beating, wooden hearts

‌In 2017, the same year that The Songs of Trees was published, a study in the journal Plant Signaling and Behavior concluded that trees have a “heartbeat” that works similarly to ours.

Roots converse with nearby bacteria. Leaves sniff the air to detect neighbors’ health and release alarm chemicals when insects attack. Trees are in constant communication.

Scientists once thought that water moved through trees by osmosis, in a somewhat continuous manner. But researcher Andras Zlinszky of Aarhus University in the Netherlands and his colleague Anders Barfod discovered that the trunks and branches of trees are actually contracting and expanding to “pump” water up from the roots to the leaves, resembling the way our hearts move blood through our bodies.

Zlinszky and Barfod used terrestrial laser scanning to monitor 22 tree species to see how the shape of their canopies changed. The measurements were taken in greenhouses at night to rule out sun and wind as factors in the trees’ movements. In several of the trees, branches shifted up and down by about a centimeter or so every couple of hours. Their theory is that this motion is an indication that trees are pumping water up from their roots.

While the researchers still don’t fully understand how this action works—they suggest that maybe the trunk gently squeezes the water, pushing it upwards through the xylem, the trunk tissue that transports water and nutrients from the roots to leaves and shoots—they say that the only difference between our pulse and that of a tree’s is that a tree’s pulse is much slower, “beating” about once every two hours. And instead of regulating blood pressure, the heartbeat of a tree regulates water pressure.

In nature, trees operate less like individuals and more as communal beings. By networking and sharing resources, they increase their resistance.

Trunk surround

Undoubtedly, we need trees. They are vital for our own survival. According to a recent report by the United Nations Food and Agriculture Organization, forests are critical for combating rural poverty, ensuring food security, providing livelihoods, maintaining biodiversity, mitigating climate change, and supplying clean air and water.

Perhaps, like the Waorani, we may have instinctively known about the similarity between trees’ and our communications all along, but we have learned to push away such seemingly “unscientific” knowledge. Throughout our cultural and literary history there are references to the songs of trees and the way that they speak: the cracking of hickories, the quaking of aspens, the sighing of oaks, the weeping of willows or the whispering of pines. Now, what was once only the province of art is becoming the realm of scholarship.

And if embracing a tree gets me closer to leaning in so that I can hear their heartbeats and learn their songs, I’ll keep on hugging trees.

Here’s to finding your true places and natural habitats,

Candy