Weeping Willow?: The Question of Plant Sentience


The environmentalist Derrick Jensen and the philosopher John Sanbonmatsu have been sparring over Lierre Kieth’s Vegetarin Myth of late. Sanbonmatsu’s arguments are so deeply nuanced and thoughtful that, contrasted with the shaking hysteria of Jensen’s outbursts, they make this entire tete-a-tete a bit of an intellectual mismatch. That said, one thing to come out of the battle was the following comment from Sanbonmatsu about the overheated topic of plant sentience. I’ll quote it at length and then end with the link to the letter from which it was excerpted.


Let’s finally move on to the main bones of contention (pun intended).  As I took pains to show, Lierre Keith explicitly and repeatedly conflates animals and plants, and dying with killing, in her book.  In his reply, Jensen merely reiterates Keith’s ontological conflations, writing that “all eating requires death.”  Yes, it does, which is why I said so in my original essay.  However, what I also said was that the fact that everything dies, or even that in living we sometimes hurt others or inadvertently cause other beings to die, cannot be a moral defense for intentionally killing or causing suffering to conscious beings.  Examined closely, Jensen’s “all eating requires death” reduces to a tautology, something along the lines of “life is life,” which is true but philosophically uninteresting.  We might just as well say that human society also “requires” death, because if people didn’t die, there would be no place to put new human beings.  But to acknowledge that “for some to live some must die” would be no justification for killing them.  In any event, while I acknowledged in my essay that agriculture, even sustainable agriculture, does lead to “collateral” mortality in nonhuman beings, I also pointed out that the animal killing apparatus kills many, many times more of those beings, both directly and intentionally (billions of animals viciously confined and manipulated and then killed each year to meet the irrational and growing demand for flesh) and indirectly, through its monopolization of the land (since more than 75% of agricultural land today is used to grow crops for animals to eat so that we can kill and eat them).

But Jensen suffers from the same cognitive incapacity as Keith:  he is unable to distinguish between sentient and insentient life.  Neither author is willing to concede any morally significant or ontological distinction, between plants and animals—such a basic distinction that practically every human culture or civilization in the history of the world has acknowledged its fundamental importance.  Jensen indeed writes:  “The soil itself—alive, with over a million beings in one tablespoon of soil, and more than a thousand different species in just a square meter of soil, all of whom must eat—requires food. Life requires death.”  This reminds me of Heidegger’s contention that what happened in the Holocaust was no different than mechanized plant agriculture:  “Agriculture is now a motorized food-industry — in essence, the same as the manufacturing of corpses in gas chambers and the extermination camps” [3].  In point of fact, as bad as industrialized agriculture is, and it is bad—indeed, as presently constituted it is just as ruinous for the planet as Keith and Jensen maintain (which is why I granted the point)—it is not genocide.  Nor is cutting one’s grass on the front stoop equivalent to cutting the throats of chickens on an assembly line or beating cats and dogs to death for their meat (as happens in Korea).  But if Jensen cannot see the moral difference between killing a child or a pig, say, both of whom are intelligent beings with emotions, and consuming bacteria in the soil, he really is beyond all help.

Yet Jensen cannot be disabused of his fantasy that plants are sentient. In my article, I maintained that no reputable scientist believes that plants are sentient, by which I meant and mean thinking and feeling and having the sensuous capacity for consciousness.  I hold to that position, with one possible and partial exception (see below).  Jensen claims that plant sentience and even consciousness is an established and widely accepted fact, the common sense of our time.  And to demonstrate the point, he cites popular scientific accounts in mainstream media journals and refers his readers to the work of scientists at the International Laboratory of Plant Neurobiology.  I confess that I had never heard of the latter.  So after learning a little about the Laboratory I contacted Frantisek Baluska, one of the lead researchers there, and asked him whether he and his colleagues really believed that plants were sentient and conscious, experienced emotions like animals, and so forth.  Baluska wrote me that while someday it “might turn [out] that…plant-specific sentience and consciousness will be even more complex than the animal/human ones,” in fact, “Unfortunately we cannot say anything about emotional lives of plants as the current science is still not matured enough to pose these questions.”  In other words, they don’t know, and they wouldn’t make the claim. 

The director of the Lab, Stefano Mancuso (cited by Jensen), answered my similar query to him with the words, “Frantisek already answered you as I would have done.”  However, Mancuso did add that “I can not imagine a living organism [of any kind] being unconscious.”  Thus, Mancuso himself seems personally to believe that plants are conscious and sentient—so chalk one up for Jensen:  the one scientist in the world, apparently.  Nevertheless, as I have just indicated, even members of Mancuso’s own research staff, whom he says he agrees with, admit that ascribing internal psychological and emotional states to plants is simply not something that the existing science permits them to do.  In his email to me, moreover, Mancuso added, “At the end [of the day] it is [also] not possible even to be sure [of] the consciousness of our brother humans, of course you know the problem of ‘other mind[s]’….”  In other words, Mancuso cannot say anything more decisive about the existence of plant consciousness than he can say about human consciousness.  These are speculative matters.  The most he and his peers can do is theorize about plant “intelligence,” without however being able to prove that they are “intelligent” in the sense of having consciousness and feelings.

My exchange with Mancuso and Frantisek led me to delve a bit further into this emerging discourse about plant sentience and “intelligence.”  Why are Jensen and Keith so intent to blur the distinction between plants and animals, a primordial ontological distinction acknowledged by most if not all human civilizations throughout history?  And why was Jensen, a back to the land primitivist, now coming out as a technoscience junkie (he cites Wired magazine and even the TED Conference, where the corporate literati now go to get their draughts of good technologic cheer)?  I found this key clue on the International Laboratory of Plant Neurobiology’s website:  the Laboratory, it says, embraces the “view [that] sees plants as information processing organisms with complex communication throughout the individual plant.”  In other words, if some of the researchers at the laboratory are comfortable speaking of plant intelligence it is because they are setting out from an essentially mechanistic way of understanding life and consciousness—as information processing.

One of the most fateful mistakes of our age has in fact been to depict consciousness and sentience as nothing more than “information processing,” and to suggest that interior mental states and experiences can be represented as algorithms and reduced to external behaviors.  This view of biology is of extremely recent vintage, the outcome of half a century of reified technological thinking about the nature of life.  More and more in the scientific literature we are seeing a reified discourse in which biological processes are being conflated with mind and feelings.  In his brief email to me, for example, Dr. Mancuso wrote of his belief that plants must experience their world sensuously because “plants are able to sense continuously and concurrently at least 20 different chemical and physical parameters; much more than any animal.”  In other words, because researchers can identify “20 different chemical and physical parameters” of information processing in plants, it seems logical to attribute sensuous experiences to them.




About James McWilliams
I'm a historian and writer based in Austin, Texas. This blog is dedicated to exploring the ethics of eating animals and animal-based products.

8 Responses to Weeping Willow?: The Question of Plant Sentience

  1. Pingback: New for September 28, 2011 : From A to Vegan

  2. William says:

    Hormonal sentience, first described by Robert A. Freitas Jr., describes the information processing rate in plants, which are mostly based on hormones instead of neurons like in all major animals (except sponges). Plants can to some degree communicate with each other and there are even examples of one-way-communication with animals.
    Acacia trees produce tannin to defend themselves when they are grazed upon by animals. The airborne scent of the tannin is picked up by other acacia trees, which then start to produce tannin themselves as a protection from the nearby animals. When attacked by caterpillars, some plants can release chemical signals to attract parasitic wasps that attack the caterpillars.
    A similar phenomenon can be found not only between plants and animals, but also between fungus and animals. There exists some sort of communication between a fungus garden and workers of the leaf-cutting ant Atta sexdens rubropilosa. If the garden is fed with plants that are poisonous for the fungus, it signals this to the ants, which then will avoid fertilizing the fungus garden with any more of the poisonous plant.
    The Venus flytrap, during a 1- to 20-second sensitivity interval, counts two stimuli before snapping shut on its insect prey, a processing peak of 1 bit/s. Mass is 10-100 grams, so the flytrap’s SQ is about +1. Plants generally take hours to respond to stimuli though, so vegetative SQs (Sentience Quotient) tend to cluster around -2.
    In theory even an organism with a hormonal system instead of a nervous system could be intelligent in some degree, but it would be an extremely slow brain, to say the least.
    And yet, at least higher plants are able to produce electrical signals, even if they do not use them in the same way animals do. František Baluška from the University of Bonn in Germany is one of the authorities on plant neurobiology.

  3. William says:

    From Wikipedia, the free encyclopedia

  4. William says:

    Plants Display Sentience and Social Behavior
    Posted by Murielle in Science & Technology, 1 Dec 2009

    Plants are sentient beings, capable of thought, communication and understanding kinship. Don’t believe me? Well, maybe some ongoing studies will convince you.

    Biologist Susan Dudley studied a group of Pale Jewelweed (Impatiens pallida) plants. Her findings—published in the American Journal of Botany—show that these flowering plants use less energy to grow roots when they are surrounded by relatives (plants that share similar genes). However, when they are amongst plants that are unrelated, their roots will grow as fast as possible. This discovery shows that plants are capable of kin recognition; meaning they are able to tell the difference between related and unrelated plants, and adjust their social behavior accordingly.

    Photo by SB_Johnny (Image source: Wikimedia Commons)
    “When I was in school, researchers assumed that some plants were better or worse than others at getting resources, but they were blind to the whole social situation. I went looking for it, and to my shock, found it. And we’ve found more of it since,” said Dudley.

    Even though the idea of a plant social structure wasn’t widely accepted, further research into plant communication happened. A lot of the focus was on plant defensive actions, such as creating toxins or how to focus resources on their immune systems. This kind of behavior led to the conclusion that plants were, indeed, able to recognize themselves. The next step in these series of studies would be to find out if and how they might respond to relatives.

    According to Plant Ecologist, Hans de Kroon, of the Radboud University in the Netherlands:

    “We know that in the animal world, kin recognition and selection plays a very important role for family structure, altruistic behavior and those kinds of things. It’s so prominent in the animal literature. Once we start to discover that plants can recognize their kin, there’s a whole set of hypotheses we can apply to studying plants that nobody ever thought to.”

    Another paper—based on further studies conducted by Dudley—revealed that American searocket plants (Cakile edentula) increased the speed of their root growth when planted amongst strangers (unrelated plants), but the speed would slow down if they were replanted with relatives. This would be the equivalent of animals of the same family or herd distributing food and water amongst themselves and keeping it away from strangers.

    Susan Dudley was not the only one interested in these plant experiments, however. Biologists Harsh Bais and Meredith Biedrzycki from the University of Delaware also ran some tests, which involved the use of Thale Cress (Arabiodpsis thaliana) seeds. The seeds were isolated in separate pots, and each pot was exposed to root secretions from other Arabidopsis plants. The results confirmed Dudley’s previous findings: how the seeds reacted depended entirely on whether the root secretions came from genetically related or unrelated plants.

    Photo by Peemus (Image source: Wikimedia Commons)
    Even more research is currently underway to find out if the roots are the only source of such communication. In Dudley’s most recent study, the possibility of plants also communicating via chemical signals emitted by their leaves also came into play. A study from earlier this year, conducted by ecologist Richard Karban, adds to this possibility. Apparently, Sagebrush will boost its immune system when exposed to clippings of a related plant. Could these plants be sending alarms or warning signals to each other? Possibly, but more research is needed to confirm anything.

    I find it absolutely fascinating that scientists are finally starting to consider plant sentience a serious possibility. The idea of plant communication is not entirely new, and has been an integral part of some spiritual practices. So, if plants are capable of communicating with each other, and understanding whether those around them are family or not, can they also feel pain? And if they can feel pain, do their relatives hear their screams when they are cooked or eaten? I think the idea of plant sentience may put a whole new perspective on things for some people. It would seem that if plants are capable of the same things as animals (realization and communication), that eating a carrot would be no different than eating a chicken leg, as both come from beings that display awareness. It certainly gives you something to think about.

    By Heidi Marshall
    Tags: plant awareness, plant communication, plant sentience, plant social behavior

  5. A very interesting topic, plant sentience. I have to side with Derrick on this one, I do think plants have a consciousness, one much different than our own, one more chemically linked, but conscious all the same.
    I think we would all be better off working towards stopping a culture that causes the useles destruction, killing and pain, rather than talking about reasons to be vegan vs non-vegan and whether plants are conscious or not, and especially before we are going to argue among ourselves. Shouldn’t we work together against the entity responsible for all the deaths, civilization? See http://deepgreenresistance.org/ for new ideas on how we can do this.
    All life requires death, but life does not require the large amount of useless deaths caused by modern culture. If no living beings ate animals, then animals would crowd out the planet and living conditions would be horrible. There needs to be a balance, and I do believe that balance includes eating both plants and animals for us humans (maybe not all of us, it is a personal choice, I mean for humans in general).
    An interesting article…I think I’m going to do more studying on plant sentience. Thank you.

  6. Greenrevolutionary says:

    There are six kingdoms of life, of which the animal kingdom is only one. Animal kingdom supremacy is no different than human supremacy.

    In fact, arguing that plants are not sentient based on their lack of similarity to animals is anthropocentric, with the unstated premise being that organisms must be able to feel or think in an anatomically similar way to the way humans (or animals) do – which is to say that the more humanlike a life-form is, the more consideration of it sentience is warranted.

    I disagree, and have to side with Lierre, Derrick and the other commenters before me – plants and all organisms are sentient, feeling, emotive. All living beings are capable of thought and of experiencing pain.

  7. BlessUsAll says:

    Derrick Jensen beautifully articulates and closely identifies with the misery of zoo animals in his book, “Thought to Exist in the Wild.” It mystifies me that he doesn’t empathize with equally the intelligent and emotional animals who he believes he has the right to kill for his dinner.

    I will never understand why people who can see and hear the violence of killing a fellow creature have the gall to defend the sentience of plants as a way of justifying their role in the obvious infliction of pain and terror on their innocent animal brethren.

  8. deveryminou says:

    Even if plants were found to be sentient, a vegan diet causes FAR less suffering than a carnivorous diet, since plants are fed to the animals who are then killed and eaten. So I call bullshit on Jensen and Keith. If they cared so much about plant sentience they would want as few plants murdered as possible: and I don’t think they really care THAT much since they have no problem eating animals and justifying their consumption with a bunch of rhetorical nonsense.

    As Konrad Lorenz said: “To any man who finds it equally easy to chop up a live dog and a live lettuce I would recommend suicide at his earliest convenience!”

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