Are trees conscious? Do they have feelings? I instantly answer my own question, of course not, confident that the world of vegetation as distinct from the world of animals and humans is devoid of any sort of awareness. Some people may become vegetarians on the grounds that animals suffer pain in the messy confines of an abattoir. With the notable exception of Descartes, most thinkers, indeed most people, take for granted that animals, particularly the more complex one most similar to humans in their makeup, share with us feelings of pain and pleasure, to say the least, and probably many other emotional states too. But we draw the line when it comes to plant life. Nobody refrains from eating fruit and vegetables to avoid cruelty to plants.
I must admit that I have never seriously questioned the view that flowers, vegetables, shrubs and trees are non-feeling entities. Does anyone believe that when an axe is embedded in its trunk, a tree feels pain? For this reason I was quite taken aback to read a review of a book in which this assumption was challenged. In The Hidden Life of trees: What They Feel, How They Communicate by Peter Wohlleben, translated by Jane Billinghurst (2016) the author tells us that his curiosity was first aroused when he investigated the stump of a very old beech tree. Why, he wondered, had it not decomposed and rotted away? Why was it still green? Studying the botanical literature he discovered that ‘the surrounding beeches were pumping sugar to keep it alive.’
I was immediately sceptical reading this. Wohlleben describes the situation in terms of purposeful action ‘to keep it alive.’ And a further cautious point, what advantage was gained, even if the other trees actually had such an aim, in keeping that stump alive? I have written other posts on a related subject, addressing the fact that there is clearly purposeful action in the non-human natural world. (See posts on this blog ‘Animal Architecture’ during January and February 2017). My favoured example has been the process of nest making among birds. But, if I have read the review correctly, Wohlleben is saying more than this. Not just purposeful action but conscious action.
Intrigued, I read on. Wohlleben thinks that trees work together to achieve certain ends, that they ‘experience pain’, even ‘make decisions’ and have characteristics like greediness and impatience. Furthermore, they ‘are aware’ of changes in temperature and can compare the lengths of days at different times of the year and ‘pass their knowledge on to the next generation’. To Wohlleben trees are conscious agents with some control over the manner of their growth.
A staple of philosophy of mind studies is Thomas Nagel’s article ‘What is it like to be a bat?’ (1974) in which the reader is invited to consider the proposition, first. that a bat is an experiencer of consciousness and then that the nature, the particular quality of that consciousness, is difficult if not impossible for humans to comprehend. Their method of echolation is surely not the same as our seeing but neither is it like our hearing. In the case of trees, which in terms of physical structure are far more remote from us than bats, without even the benefit of crude analogies with seeing and hearing, we cannot have the slightest inkling of their state of mind. Nevertheless, as Wohlleben argues (and to pick up Nagel’s phrase), there is ‘something it is like’ to be a tree. Can he say anything about tree consciousness? He offers ‘a diffuse, blind intelligence located in the sensitive, questing filaments of thousands of root-tips, or a networked language of chemical messages, fanning out through the forest floor via a “wood wide web” of symbiotic fungal mycelium.’ Make of that what you can.
To maintain the status quo, to uphold the received wisdom of the western philosophical tradition which places vegetation in all its forms outside the boundaries of consciousness, I am inclined to say that however complex the reactions of trees may be, they can be accounted for in terms of chemical processes and that, therefore, there is no need to invoke consciousness in a full description of what is taking place. But I am a little reluctant to lean on accepted wisdom without at least a pause for reflection.
According to Wohlleben trees can ‘taste’ which species of pest has bitten into their leaves and in response send out an appropriate chemical compound as a form of resistance. They even emit messages to other nearby trees which then release the same compounds as protection against likely attack: ‘When umbrella thorn acacias are nibbled by giraffes they release ethylene which deters them; but the chemical also drifts to nearby acacias, and “all the forewarned trees also [pump] toxins into their leaves to prepare themselves.” ’
I am sure that many readers will take the line that even these very subtle and sophisticated responses are evidence only of the operation of highly complex chemical systems, physical cause and effect in accordance with natural law without the accompaniment of any feeling.
But even if that explanation is accepted, it is not the end of the story. There is a link here to a deeply unsettling and difficult philosophical problem, namely that of other minds. It can be argued that all we witness in the behaviour of others, whether it is in the form of facial expressions, movements, cries, calls or, in the case of humans, speech is in one sense reducible to biological and chemical reactions. Lips move, fists clench, sound waves are emitted and so on. The only conscious states that are known are our own. Trees protect themselves against pests, animals fight against predators, humans talk to one another in a war cabinet. It’s chemistry, chemistry, chemistry? Or am I getting the wrong end of the stick?
So where does consciousness, what we know indubitably and at first-hand, come in?
(Wohlleben’s book was reviewed by Francis Gooding in the London Review of Books, 16th February 2017.)