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Chatter

Silent Conversations: How Trees Talk to One Another

By Lily McCann

There are so many conversations that go on beyond our hearing. This column explores communication between trees and how it might change the way we perceive them.

Edited by Ethan Newnham, Irene Lee &  Niesha Baker

Issue 1: September 24, 2021

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Illustration by Rachel Ko 

It’s getting brighter. A long, long winter is receding and warm days are flooding in. I’m not one for sunbathing, but I love to lie in the backyard in the shade of the gums and gaze up into the branches. They seem to revel in the weather as much as I do, waving arms languidly in the light or holding still as if afraid to lose a single ray of sun. If there’s a breeze, you might just be able to hear them whispering to one another.

There’s a whole family of these gums in my backyard and each one is different. I can picture them as distinctly as the faces of people I love. One wears a thick, red coat of shaggy bark; another has pale, smooth skin; a third sheds its outer layer in long, stringy filaments that droop like scarves from its limbs. These different forms express distinct personalities. Gum trees make you feel there is more to them than just wood and leaves.

There’s a red gum in Central Victoria called the ‘Maternity Tree’. It’s incredible to look at. The huge trunk is hollowed out and forms a sort of alcove or belly, open to the sky. Generations of Dja Dja Wurrung women have sought shelter here when in labour. An arson attack recently blackened the trunk and lower branches, but the tree survived (1). 

Such trees have incredibly long, rich lives. Imagine all the things they would say, if they could only tell us their stories. 

Whilst the ‘whispering’ of foliage in the wind may not have significance beyond its symbolism, there are other kinds of communication trees can harness. All we see when a breeze blows are branches and leaves swaying before it, but all the time a plethora of tiny molecules are pouring out from trees into the air. These compounds act like tiny, encrypted messages riding the wind, to be decoded by neighbours. They can carry warnings about unwanted visitors, or even coordinate group projects like flowering, so that trees can bloom in synchrony. 

If we turn our gaze lower we can see that more dialogue spreads below ground. Trees have their own telephone cable system (7), linking up members of the same and even different species. This system takes the form of fungal networks, which transfer nutrients and signals between trees (3). Unfortunately, subscription to this network isn’t free: fungi demand a sugar supply for their services. Overall, though, the relationship is beneficial to both parties and allows for an effective form of underground communication in forests.  

These conversations are not restricted to deep-rooted, leaf-bearing beings: trees are multilingual. A whole web of inter-species dialogue murmurs amongst the branches beyond the grasp of our deaf ears. Through the language of scent, trees entice pollinators such as bees and birds to feed on their nectar and spread their pollen (4). They warn predators against attacking by releasing certain chemicals (5). They can even manipulate other species for their own defence: when attacked by wax scale insects, a Persimmon tree calls up its own personal army by alerting ladybugs, who feed on the scales, averting the threat to the tree (6). 

Such relationships demonstrate the crucial role trees play in local ecosystems and their essentially cooperative natures. Trees can be very altruistic, especially when it comes to family members. Mother trees foster the growth of young ones by providing nutrients, and descendants support their elderly relatives - even corpses of hewn-down trees - through their underground cable systems.

These intimate, extensive connections between trees are not so different from our own societal networks. Do trees, too, have communities, family loyalties, friends? Can they express the qualities of love and trust required, in the human world, for such relationships? This thought begs the question: Can trees feel?

They certainly have an emotional impact on us. I can sense it as I lie under the gums. Think about the last time you went hiking, sat in a tree’s shade, walked through a local park. There’s something about being amongst trees that calms and inspires. Science agrees: one study has shown that walking in forests is more beneficial to our health than walking through the city. How do trees manage to have such a strong effect on us?

Peter Wohlleben, German forester and author of The Hidden Life of Trees, suggests that happy trees may impart their mood to us (9). He compares the atmosphere around ‘unhappy’ trees in plantations where threats abound and stress signals fill the air to old forests where ecosystem relations are more stabilised and trees healthier. We feel more relaxed and content in these latter environments. 

The emotive capacity of trees is yet to be proven scientifically, but is it a reasonable claim? If we define happiness as the circulation of ‘good’ molecules such as growth hormones and sugars, and the absence of ‘bad’ ones like distress signals, then we may suggest that for trees an abundance of good cues and a lack of warnings could be associated with a positive state. And this positive state - allowing trees to fulfill day-to-day functions, grow and proliferate, live in harmony with their environment - could be termed a kind of happiness in its own right. 

This may seem like a stretch - after all, how can you feel happiness without a brain? But Baluska et al. suggest that trees have those too, or something like them: command centres, integrative hubs in roots functioning somewhat like our own brains (10). Others compare a tree to an axon, a single nerve, conducting electrical signals along its length (11). Perhaps we could say that a forest, the aggregate of all these nerve connections, is a brain.

Whilst we can draw endless analogies between the two, trees and animals parted ways 1.5 billion years ago in their evolutionary paths (12). Each developed their own ways of listening and responding to their environments. Who’s to say whether they haven’t both developed their own kinds of consciousness?

If we take the time to contemplate trees, we can see that they are infinitely more complex and sensitive than we could have imagined. They have their own modes of communicating with and reacting to their environment.

The fact is, trees are storytellers. They send out a constant flow of information into the air, the soil, and the root and fungal systems that join them to their community. 

Even if we can’t converse with trees in the same way that we converse with each other, it’s worth listening in on their chatter. They could tell us about changes in climate, threats to their environment, and how we can best help these graceful beings and the world around them. 

References:


1. Schubert, Shannon. “700yo Aboriginal Maternity Tree Set Alight in Victoria.” www.abc.net.au, August 8, 2021. https://www.abc.net.au/news/2021-08-08/dja-dja-wurrung-birthing-tree-set-on-fire/100359690.

2. Pichersky, Eran, and Jonathan Gershenzon. “The Formation and Function of Plant Volatiles: Perfumes for Pollinator Attraction and Defense.” Current Opinion in Plant Biology 5, no. 3 (June 2002): 237–43. https://doi.org/10.1016/s1369-5266(02)00251-0.; Falik, Omer, Ishay Hoffmann, and Ariel Novoplansky. “Say It with Flowers.” Plant Signaling & Behavior 9, no. 4 (March 5, 2014): e28258. https://doi.org/10.4161/psb.28258.

3. Simard, Suzanne W., David A. Perry, Melanie D. Jones, David D. Myrold, Daniel M. Durall, and Randy Molina. “Net Transfer of Carbon between Ectomycorrhizal Tree Species in the Field.” Nature 388, no. 6642 (August 1997): 579–82. https://doi.org/10.1038/41557.

4. Buchmann, Stephen L, and Gary Paul Nabhan. The Forgotten Pollinators. Editorial: Washington, D.C.: Island Press/Shearwater Books, 1997.

5. De Moraes, Consuelo M., Mark C. Mescher, and James H. Tumlinson. “Caterpillar-Induced Nocturnal Plant Volatiles Repel Conspecific Females.” Nature 410, no. 6828 (March 2001): 577–80. https://doi.org/10.1038/35069058.

6. Zhang, Yanfeng, Yingping Xie, Jiaoliang Xue, Guoliang Peng, and Xu Wang. “Effect of Volatile Emissions, Especially -Pinene, from Persimmon Trees Infested by Japanese Wax Scales or Treated with Methyl Jasmonate on Recruitment of Ladybeetle Predators.” Environmental Entomology 38, no. 5 (October 1, 2009): 1439–45. https://doi.org/10.1603/022.038.0512.

7, 9. Wohlleben, Peter, Jane Billinghurst, Tim F Flannery, Suzanne W Simard, and David Suzuki Institute. The Hidden Life of Trees : The Illustrated Edition. Vancouver ; Berkeley: David Suzuki Institute, 2018.

10. Baluška, František, Stefano Mancuso, Dieter Volkmann, and Peter Barlow. “The ‘Root-Brain’ Hypothesis of Charles and Francis Darwin.” Plant Signaling & Behavior 4, no. 12 (December 2009): 1121–27. https://doi.org/10.4161/psb.4.12.10574.

11. Hedrich, Rainer, Vicenta Salvador-Recatalà, and Ingo Dreyer. “Electrical Wiring and Long-Distance Plant Communication.” Trends in Plant Science 21, no. 5 (May 2016): 376–87. https://doi.org/10.1016/j.tplants.2016.01.016.

12. Wang, Daniel Y.-C., Sudhir Kumar, and S. Blair Hedges. “Divergence Time Estimates for the Early History of Animal Phyla and the Origin of Plants, Animals and Fungi.” Proceedings of the Royal Society of London. Series B: Biological Sciences 266, no. 1415 (January 22, 1999): 163–71. https://doi.org/10.1098/rspb.1999.0617.

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