Douglas fir tree. Photo by Dog Walking Girl, Wikimedia Commons
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Peter Wohlleben is a German forester. He published an extremely popular book three years ago entitled The Hidden Life of Trees: What They Feel, How They Communicate- Discoveries From a Secret World. Wohlleben described the natural community of trees in a forest and explored many ecological details of a number of common tree species. Instead of speaking in a careful, calculated scientific “voice,” though, he used a simple and very vivid anthropomorphic syntax to describe the trees’ “needs,” “feelings” and “desires.”
He described parental trees “loving” their offspring. He described healthy trees “pitying” their fallen or sickened companion trees (and also sending on some of their precious photosynthetic sugar production to keep them alive). He talked about trees being “friends” with each other and warning each other of dangers. He condensed the ecological matrices of several types of trees into descriptions of the trees being “sociable but sometimes bullies” (beeches), or “cold and unfeeling” (birches) or “loners” (willows).
Wohllenben states that he does not talk to trees, but the flow of his book suggests that he does listen to them very closely. He also states that in spite of their “feelings” and “emotions” trees should be cut down and their wood should be used for construction, for furniture and for fuel (not to mention for paper for his books!). The scientific foundations behind his anthropomorphisms are extensive, but this science gets overshadowed by the emotionality of his tree-creature images.
Giant Sequoia. Photo by D. Sillman
Wohllenben has been roundly criticized by ecologists and foresters for his imaginative but simplistic descriptions and discussions of trees and forest ecology. An online petition circulated by University of Gottingen scientists protesting Wohllenben’s appearance at a German literary festival called for “facts not fairy tales.” The petition stated: “It is very unfortunate … that, through this book, so many people obtain a very unrealistic understanding of forest ecosystems because the statements made here are a conglomerate of half-truths, biased judgments, and wishful thinking derived from very selective and unrepresentative sources of information.”
Wohllenben shrugs off these criticisms and claims, with some accuracy, that all of his summary descriptions of trees are based on published science. Many admirers of Wohllenben’s book have in turn heaped derision on his scientist critics. They referred to science or at least writing in science as “grey, dull and soulless” and praise books like Hidden Life of Trees as an antidote to the turgidity and lifelessness of scientific writing.
Since I have in my career as a teacher and, in retirement, as a writer always tried to express and explain scientific ideas not only clearly but with all of the energy and life they so richly deserve, I was really put off by the “grey, dull, soulless” description. I read Wohllenben’s book from the perspective that his sometimes fairy tale-like descriptions of the trees were ways to open the door into deeper discussions, and I trusted that he had a sound enough knowledge of forest ecology not to lose his way in his anthropomorphisms. I am afraid, though, that many readers come away from his chapters with the ideas that forests are social clubs of sentient trees rife with emotionally charged friendships and enmities. There are incredibly elegant and much more interesting pictures of the living realities of these trees hidden beneath the simplified surface of his book. These would make a much richer story for scientists and non-scientists alike!
Douglas firs. Photo by Born 1945, Flickr
For example, Suzanne Simard is a professor of forest ecology at the University of British Columbia, and her work has been frequently cited by or alluded to by Wohllenben. Specifically, Dr. Simard uses organic molecules into which radioactive carbon atoms have been inserted to track the flow of nutrient molecules (like sugars) and communication molecules (like growth factors and hormones) between trees. Simard has shown that in a mixed forest of Douglas fir and paper-bark birch all of the trees are interconnected at their roots by a network of mycorrhizal fungi (a system that Wohllenben refers to as the “Wood Wide Web”), and that sugars are exchanged between firs and birches along this root/fungi network.
Most interestingly, this exchange occurs both from birch to fir and also from fir to birch depending on the season and on specific site conditions. In the fall, when the birches lose their leaves and stop photosynthesizing, sugars from the evergreen and, thus, still photosynthesizing fir trees are transferred to the birches. During the summer, though, sugars are transferred from the leafed out and more robustly photosynthesizing birches to the firs. This transfer of sugars especially goes to those firs that are photosynthetically inhibited because they are growing in the shade of other trees.
This is a coevolutionary association in which two different species of trees via their root interconnections are able to reduce seasonal or environmental stress! The sugars are probably moving under diffusion gradients from high concentration tissues into lower ones, and there is no “intention” involved on the part of either tree. The resulting reduction in stress, though, allows higher rates of survival and growth and increased rates of reproduction in both the firs and the birches.
Wohllenben would say, however, that these two tree species are “friends” and that they are “taking care of each other.” His descriptions leave out the incredible elegance of the ecology, physiology and evolution of this association and drapes a cover of human emotions over a fascinating interspecific symbiosis!
Douglas fir with saplings. Photo by BLM
Dr. Simard has also described “hub trees” in the Douglas fir forest. These trees are mature, older trees that are producing seed (and seedlings) and that have a dense extension of their roots and root -associated mycorrhizal fungi that radiate out through the surrounding soil. These roots and fungi make contact with almost all of the other trees growing in the forest, but in particular, they make extensive and quite robust interconnections with seedlings that are genetically similar to the hub tree. In other words, the “mother tree” makes contact with its “offspring” probably through recognition of similarities in cellular surface proteins!
A “mother” Douglas fir, then, is able to transfer significant amounts of its own photosynthetically generated sugar preferentially to its progeny seedlings via these root/mycorrhizal connections. The “mother” tree is thus able to assist the growth and survival of its offspring and accomplish a very fundamental step in Darwinian selection! Trees that are able to make these connections and “recognize” their offspring will be able to more efficiently pass along their own DNA to future generations and have their offspring and genes make up an increasingly large proportion of the future population of Douglas firs!
Douglas fir. Photo by Wildcat Dunny, Flickr
The elegance and intricate (and immensely logical) mechanisms by which this evolutionary hegemony is accomplished is quite lost when Wohllenben simply states that these fir trees “suckle” their young.
Wohllenben tells children stories about some very complex realities, but, I am afraid that he leaves too much out! We have to read his book as a collection of hints about the true wonder of tree existence out in Nature. And besides, I could never think of beeches as “bullies” nor of birches as “cold and unfeeling.” They are trees! We should try to understand them for what they really are!
I haven’t yet read this book — but now I will need to read it.
Right now I agree strongly with Jennifer that we shouldn’t try to analogize any sort of anthropomorphism to trees (or to any vegetation). Any such analogy is so remote as to be worth ignoring. Instead, I think the focus should be on how plant and animal behavior *differs.* That would be more instructive.
On the other hand, let’s not make a remote analogy, if any, to the understanding of anthropomorphic similarities of communication between humans and other high-order animals (including birds). As recently as the early 1990s (I think it was around then), Donald Griffin prompted nothing but laughter in reaction to his classic book Animal Minds. It required a couple decades of exhaustive research for us to realize how correct he was.
Again, I agree that there’s nothing but a vague and perhaps meaningless analogy between plants and animals in this regard. But I hate to reject categorically any analogy, no matter how remote, between plant and animal behavior. After all, who but Leonardo was certain in his time that humans would someday find a way to fly.
I happen to be in a philosophical mood today, eh Bill?
I was enchanted by The Hidden Life of Trees (and more recently The Overstory by Richard Powers–very much a novel). Your points are very well taken, though, dear Bill: trees aren’t humans in tree form. There’s a certain amount of hubris in force-fitting the lives of trees into our limited range of perception and feeling. Thanks for all you do to convey the wonders of science so elegantly, intricately and logically!