What do you see when you look at a tree?
Perhaps you notice its age and wonder what events occurred in its lifetime. Maybe you think about the nesting birds it harbors or what value it would bring as lumber. You might admire the elegance of its branches and feel inspired by its beauty.
But did you ever think of a tree as a social being with the capacity to communicate with – and help – other trees?
Peter Wohlleben, author of the new book The Hidden Life of Trees, makes the case that trees are “unique individuals” that feel pain, learn from experience, make decisions, exchange information and nurse sick and injured brethren trees.
A German forester, Wohlleben studied research by scientists from around the world and concluded that humans are wrong in assuming trees lack intelligence because they don’t have brains.
Trees, he points out, live their lives “in the slow lane” … on a completely different time scale from humans. One of the world’s oldest trees is a spruce in Sweden believed to be more than 9,500 years old, or 115 times longer than the average human lifetime. Even relatively young trees 100 years old are older than most people!
In his book, Wohlleben uses human-friendly descriptions to explain the science of tree lives. He describes tree friendships, the “language” that trees use to communicate, and how being part of a community – a forest – helps trees live longer.
Wohlleben tells of stumbling upon a circular patch of “strange-looking mossy stones” in a preserve of beech trees. Upon investigation, he discovered that they weren’t stones at all, but the ancient remnants of a tree stump. When he scraped away some bark, he was amazed to find a greenish layer underneath, meaning the wood was still alive. But how could it survive without leaves?
“It must be getting assistance from neighboring trees, specifically from their roots,” he concluded. “Scientists investigating similar situations have discovered that assistance may either be delivered remotely by fungal networks around the root tips – which facilitate nutrient exchange between trees – or the roots themselves may be interconnected.”
One thing was clear to Wohlleben: the surrounding beeches were pumping sugar to the stump remains to keep it alive. He believes this is an example of trees helping each other through a social network, which he dubs the “wood wide web.” His research further found that trees not only share food with their own species, but sometimes nourish other species.
Why would trees help other trees, which are competitors for sunlight and water?
“The reasons are the same as for human communities: there are advantages to working together,” Wohlleben wrote. “On its own, a tree cannot establish a consistent local climate. It is at the mercy of wind and weather. But together, many trees create an ecosystem that moderates extremes of heat and cold, stores a great deal of water and generates a great deal of humidity. And in this protected environment, trees can live to be very old.”
If every tree were looking out only for itself, he notes, most would never reach old age. Regular fatalities would result in many large gaps in the tree canopy, making it easier for storms to penetrate the forest and uproot even more trees.
Unseen by humans, the author said, trees communicate information to each other, even warning about danger.
Wohlleben tells about umbrella thorn acacia trees in Africa favored by giraffes. Once giraffes start nibbling, the acacias pump a toxic substance into their leaves to repel the animals. But that’s not all: the trees also emit a “warning gas” that tells neighboring acacia trees to start producing the same toxins. The giraffes seem to know this, Wohlleben said, and don’t bother stopping at nearby trees; they proceed to acacias too far away to have been forewarned.
Trees don’t rely exclusively on airborne scent to communicate. Wohlleben cites a study showing that trees also warn each other by sending chemical signals through the fungal networks around the root tips. Electrical impulses transmitted through roots are yet another way trees send “news bulletins” to each other.
Trees also have a sense of taste and can tell what insect predators are munching their leaves. “The saliva of each (insect) species is different, and trees can match the saliva to the insect,” wrote Wohlleben. The tree then releases the precise pheromones needed to summon beneficial predators. For example, elms and pines can summon small parasitic wasps that lay their eggs inside caterpillars, killing them.
Read Wohlleben’s book, and you’ll never look at trees the same way again! It may even inspire you to become a tree hugger, an old phrase now with new meaning.
To learn more about the book, check out author interviews at the Yale Environment 360 website at http://e360.yale.edu/features/are_trees_sentient_peter_wohlleben and on YouTube at https://www.youtube.com/watch?v=1djibBPOfto.
Hug a tree today! And to learn about preserving New Jersey’s forests and open space, visit the New Jersey Conservation Foundation website at www.njconservation.org or contact me at firstname.lastname@example.org.
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