Trees — the Other Social Network
There have been some intriguing scientific breakthroughs lately in our understanding of the plant kingdom. I just finished reading a fascinating new book, The Hidden Life of Trees, by Peter Wohlleben, who was a forester in Germany for decades. He draws from research far and wide, mostly the pioneering work begun 30 years ago by Suzanne Simard at the University of British Columbia. Imagine you’re standing on the street in any city. Hidden beneath the pavement is a maze of cables carrying phone or electricity, gas lines, water and plumbing. It forms the city’s communication system.
The forest is the same way, and especially so for trees, whose root systems extend to about the size of the visible canopy of leaves and branches above. Connected to the root tips are tiny fungal threads called hyphae, about the size of sewing thread, which make up a larger nexus called mycelia (some of the world’s largest organisms have been found to be vast fields of mushrooms, interconnected underground). So what’s in it for the fungi? A piece of the action, in the form of sugar and carbohydrates. What service do they provide in turn? The creation of what Simard calls the “wood wide web.” Think fiber optics. (Ironically, a group of fiber optic cables bundled together is called a trunk line.)
Science evolves, too, as growing knowledge supplants old ideas with new ones. Decades ago we thought that young trees grow fastest and older ones more slowly. Now we know the opposite is the case. The key to long life for a tree is to grow slowly when young, building strength so as not to be vulnerable to storms or high winds. I’ve never liked the term “forest management,” though I understand the mindset of looking at trees as board feet of lumber. The forest can manage quite well without our help. Yes, trees compete with each other for sunlight and space, but there’s more cooperation than conflict. It’s all about what’s good for the whole, not the individual, which the Right calls communism, or at the least, socialism. I guarantee you won’t find many libertarian trees out there anywhere, outside of a stray seed the wind blew into a rocky crevasse. Another old idea is that of controlling pests with harmful chemicals. This kind of thinking is typical in a dysfunctional society where only short term gain is valued. A good example is the spruce budworm. Left alone it can decimate a large portion of a forest, clearing large new sunlit areas where flowers can thrive. Flowers attract insects, which attract birds, which feast on the spruce budworm. That’s forest management.
It turns out that trees are social beings. Because of their interconnectedness, not only can they identify other family members, but kin of the same species, as well as others. Trees can “see,” by way of the light sensors in the leaves. They can feel if not pain, at least discomfort. An insect bites into the bark. The tree analyses its saliva, and begins to produce a chemical making its flesh a little more disagreeable. It can also send chemical signals through the air to the others, as a warning. Trees are capable of producing up to 3000 different chemical compounds. That’s a pretty impressive laboratory. How much information is in those signals, I wonder. Are they a kind of language?
Young saplings get little sunlight, beneath the leaf canopies of the adults, so Mother trees furnish them with nutrients. Simard helped discover these maternal tendencies. Hub trees, usually the eldest, may be in contact with dozens of others. A sick tree may be fed by many other trees in the vicinity. If it dies it could open a gap for wind to break off branches of other trees, making them more vulnerable to insect or bacterial attack. Again, as with the Three Musketeers, it’s all for one and one for all. A tree is only as strong as the forest around it. We don’t think of them as being mobile, yet they can be immigrants. Right now, due to global warming, several Southern and tropical species are migrating North (better build that wall quickly, President Rump), as they did after the end of the last ice age. It may take hundreds of years, but remember they are operating with a different sense of time than ours. J.R.R. Tolkien had it right with his ents.
Conifers (evergreens with needles) create antifreeze so their needles don’t freeze and die. In summer they cover the needles with a waxy coating to conserve water. Notice that many conifers grow their branches a little downward. That’s so that heavy snowfall drops off, preventing the branches from breaking. Deciduous trees (lose their leaves in winter) grow their branches slightly upwards so that rain runs down them to the trunk and root system. All trees in temperate or polar regions, whether deciduous or evergreen, hibernate. After a rigorous growing season, they’re exhausted, so they go into a dormant period, saving their energy for spring, when it will be most needed (it’s why dormancy is usually a good time for pruning). Trees in cities with perpetual lighting actually suffer from sleep deprivation, so they’re more vulnerable to insects or diseased. After a heavy winter, deciduous trees will leaf out sooner. Trees can count. They are aware of the passage of time. They can “see” the days getting shorter or longer. And they remember. In fact, as with animals, it seems their memory is epigenetic, meaning it’s passed on to future offspring.
I want to inject a note here that all plants exhibit similar properties, to a greater or lesser extent. I chose trees because they are the oldest well-adapted beings in the plant kingdom, hence the most evolved. Conifers first appeared 300 million years ago, and deciduous trees about 150 million years ago (followed by the triumph of flowering plants — the most efficient means of propagation — about 125 million years ago). There are bristlecone pines in the Rocky Mountains that are 5000 years old. And because they live so long compared to other plants, I rather like the idea of wisdom coming with age. I’m grateful again for journalist Michael Pollan, who writes a lot about food and plants (The Omnivore’s Dilemma, The Botany of Desire). I recommend him highly, especially an article he wrote for The New Yorker (Dec. 23, 2013), called “The Intelligent Plant.” That’s where I learned about Mancuso’s work.
How are all these “decisions” getting made? Well, that’s a loaded word. I prefer “intent.” This is where we get into debates about intelligence, sentience, and self-awareness. That’s a problem, because the only examples we have of these things are ourselves, so we’re already biased. If intelligence is defined as being self-aware, then we can’t tell, yet. Mancuso sees it differently; he defines intelligence as the ability to solve problems. In one of his experiments he set up a time lapse camera on young bean plants with a metal cylinder about two feet away. The bean plants were “looking” for something to climb, and they moved toward the cylinders, time after time. How could they sense the presence of the cylinders? We know they have photoreceptors in their leaves, but those are thought to be for detecting light levels.
We tend to think creatures with brains are the most evolved. Plants don’t have brains, so they can’t have neurons or a nervous system. They do, however, have structures analogous to neurons, and even create the neurotransmitters serotonin, dopamine, and glutamate. Structures analogous to brains have been found near the root tips, or radicles, of plants. I was astounded to learn who first discovered them — Charles Darwin, who late in life became passionate about botany. In his 1880 book The Power of Movement in Plants, he wrote “it’s hardly an exaggeration to say the tip of the radicle, having the power of directing the movement of the adjacent parts, acts like the brain of one of the lower animals.”
Mancuso makes an interesting point that for a creature which is immobile for its entire life, a brain or vital organs can be a disadvantage. A plant can lose as much as 90% of its mass and still survive; not many animals can do that. Because they are immobile, they have to be more intensely tuned in to their immediate environment. Mancuso informs us that because plants are sensitive and intelligent beings, we are obliged to treat them with respect. To the American Indians, they were the tree people. They referred to themselves as human beings, but all the creatures were other people; that’s respect. These recent breakthroughs have also changed Peter Wohlleben’s perspective, as towards the end of his book he says, “When you know that trees experience pain and have memories and that tree parents live together with their children, then you can no longer just chop them down and disrupt their lives with large machines.”
Not yet become a Buddha,
This ancient pine tree,
— Kobayashi Issa (1763-1828)