It's Earth Month: Let's talk about – and listen to – trees (they speak!)

There is a growing body of evidence that trees "talk." April is Earth Month. Now's a good time to approach trees with open arms, heightened senses and new respect.
April 1, 2024
Ethan Gelber
Content Director
“I am the Lorax who speaks for the trees, which you seem to be chopping as fast as you please!”
– Dr. Seuss, The Lorax

Some of the greatest scientific breakthroughs – discoveries, but also theories – took a long time to find an appreciative public, let alone traction among other scholars. A few epic examples: heliocentric solar system, evolution, genetics, complex numbers, plate tectonics, radio waves, relativity, quantum mechanics.

Even today, some new innovative ideas are slow-moving revelations. In a time of incontestable and dramatic human-driven climate change, arguably the most remarkable ideas have to do with the environment. And one of them, though it seems to pull from the pages of fantasy fiction, could fill gaps in our understanding of nature that change our approach to, well, everything:

There is a growing body of evidence that trees "talk." 

Certainly they communicate with one another but may also, one day, be comprehensible to people. We just have to learn how to listen.

Tree speech champions

The two most outspoken, and somewhat controversial, advocates for this theory are Peter Wohlleben, a German forester and author of The Hidden Life of Trees: What They Feel, How They Communicate, and Suzanne Simard, a Canadian professor of forest ecology who has done extensive research into hyperlinked “hub trees,” as she calls them in scientific papers, or “mother trees."

The basic concept is that, as described by Wohlleben, all trees “in every forest that is not too damaged, are connected to each other through underground fungal networks. Trees share water and nutrients through the networks, and also use them to communicate. They send distress signals about drought and disease, for example, or insect attacks, and other trees alter their behavior when they receive these messages.”

Some people have labeled it the ‘wood-wide web,' but scientists call them mycorrhizal networks, a phenomenon extensively studied by Simard. She has reported that "One teaspoon of forest soil contains miles of fungal filaments.”

To communicate with one another, trees send signals through this network. And now these chemical, hormonal and slow-pulsing electrical signals are being deciphered by scientists like Edward Farmer at the University of Lausanne in Switzerland. What he has identified appears strikingly similar to animal nervous systems.

“Trees have long been trying to reach us. But they speak on frequencies too low for people to hear.”
– Richard Powers, The Overstory

Smart tree sense

It gets even better. Trees can also communicate through the air, using pheromones and other scent signals. A much-cited 1990 South African study revealed that acacia trees send an ‘alarm signal’ to other trees when antelope graze on their leaves. The leaves produce a tannin that is lethal in sufficient quantity, as well as emit an ethylene into the air that can travel up to 50 yards. Nearby acacias pick this up as warning of the threat and then start producing their own leaf tannin.

More recently, Monica Gagliano has gathered evidence at the University of Western Australia that some plants may also make and detect sounds, such as crackling noises in their roots. These have been registered at a frequency of 220 hertz, inaudible to humans, but perhaps some of us are more susceptible than others, as this Redditer reported. Similarly, researchers at the University of Missouri demonstrated that some trees reacted negatively to the sound vibrations of munching caterpillars.

Equally exciting, František Baluška a professor at the University of Bonn has been exploring plant intelligence, as evidenced by the ability to retain memories and relay them to offspring. This has been accomplished by temporarily sedating plants and watching their behavior as they reawaken, something that can only happen to things with consciousness. 

And then there’s András Zlinszky, a scientist at the Balaton Limnological Institute in Hungary, who initially believed to have identified sleep behavior in trees (cyclically rising and falling tree branches) but, upon closer examination, now sees it as a very, very slow “heartbeat” used to move water around, among other things. 

Tree your mind

April is Earth Month. It’s a time during which to increase our environmental awareness and think more intentionally about coexisting with nature. What better moment is there to talk and listen to trees? As Wohlleben says: “Plants ignore noises that pose no threat to them. These noises probably include human voices.” So rather than sneaking up with saws in hand, let’s approach them with open arms, heightened senses and new respect.

P.S. Today is April Fool’s Day! But, get this: All of the above is 100% true. It’s good to read like a skeptic, but much more fun to embrace the fantastic.