Do trees have brains?

“THUS, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows.” So wrote Charles Darwin in the last paragraph of On the Origin of Species. The sense one gets is that all species below the ‘higher animals’ are in some inferior products of evolution by natural selection. But is there more to the lower forms of life, even to plant life than this? Well, according to Peter Wohlleben in The Hidden Life of TREES, there most certainly is.

Indeed, the titles of his chapters tell their own stories. Titles like ‘Friendships’, ‘The Language of Trees’ and ‘Social Society’ sound more like a sociological thesis than a book on trees. Writing about the culture of trees, he writes: “It appears that nutrient exchange and helping neighbours in times of need is the rule, and this leads to the conclusion that forests are super organisms with interconnection much like ant colonies.” Not only that, trees are able to recognise their own roots from those of others and ‘even from the roots of related individuals’. On the other hand, the delinquents of the tree world are planted coniferous forests, which cannot network with each other because their ‘roots are irreparably damaged when they are planted’.

When Wohlleben started writing the book he managed the forest in the Eifel mountains in Germany and it began to change his experience of the forest. “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.”

We believe that language can only take place via human and some other ‘higher’ species using words, symbols or signs. However, there are different ways of communicating and trees in particular communicate using scent. For example, it was noticed in the African savannah that acacia trees can give off a warning gas to signal to others that they are under attack.

Beeches, spruce and oaks ‘all register pain as soon as some creature starts nibbling them.’ In fact, writes Wohlleben, trees communicate through smell, vision and electrical impulses. And if trees can demonstrate something akin to friendship, then it seems that they also have something resembling a social security system. In undisturbed beech forests, trees share resources by synchronising their photosynthesis levels so that they are all ‘equally successful’. “The trees, it seems, are equalizing differences between the strong and the weak.”, writes Wohlleben.

Now, perhaps the most controversial claim made by Wohlleben is his contention that trees have brains. He argues that since studies show that trees can learn, they must be able to store their knowledge. Nevertheless, the idea that trees have a brain may sound to some like a bit of a stretch. Wohlleben writes: “For there to be something we would recognise as a brain, neurobiological processes must be involved, and for these, in addition to chemical messages, you need electrical impulses.

“And these are precisely what we can measure in trees, and we’ve been able to do so since as far back as the nineteenth century.” Brain-like structures can be identified at root tips, and a powerful analogy can be found in the use of the word ‘dendron’ (from the Greek meaning ‘tree’) for certain processes in the human brain.

An interesting question is whether all of this has any resonance with the concept of human consciousness. Of course, we have to be cautious here because it has not yet been established whether or not trees do actually have a brain. But we can get round that by using the conditional if/then. So, we can say, if trees have brains, then does that help in our understanding of consciousness?

Well, one of the markers of consciousness is intensionality or aboutness. That is, for an organism to have consciousness it must be able to be aware of stuff outside of itself. One of the claims by those who are opposed to the idea that the material brain has consciousness is that intensionality has no place in pure matter. But if organisms like trees can be said to have inensionality, then this strut of the anti-materialists is knocked away. This is not the end of the matter, however, because there more struts for the anti-materialists to cling to.