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In response to: 
“Plants are sentient and have feelings too!”

Article

This objection to animal rights and veganism is usually not from a concern for the well-being of plants but to illuminate a perceived inconsistency. If both plants and animals are sentient and have feelings, and if we abstain from eating animals for ethical reasons, then we must also abstain from eating plants.

Claims of plant sentience and intelligence make for provocative titles and seductive clickbait, but a closer consideration of the evidence renders these claims vacuous.

Plants differ from animals in ethically significant ways.

Plants cannot feel pain. Because plants lack a brain, a central nervous system, and pain receptors, they cannot feel pain. Plants may sense they are being eaten through mechanoreceptors, but they don’t care.1“We Asked a Biologist If Plants Can Feel Pain.” Vice. Accessed July 26, 2017. https://www.vice.com/en_us/article/xd74nd/we-asked-a-botanist-how-sure-science-is-that-plants-cant-feel-pain-302

Plants cannot experience emotions. Emotions are processed in the hippocampus and amygdala regions of the brain  neither of which are present in a plant.2Rand S. Swenson, M.D., Ph.D., “Review of Clinical and Functional Neuroscience.” Dartmouth Medical School, 2006. https://www.dartmouth.edu/~rswenson/NeuroSci/chapter_9.html

Plants have no self-awareness or sense of the future. Thinking requires a brain, and without thought, there can be no self-awareness or sense of the future.

Plants do not have desires, preferences, or interests. There is no evidence that plants have the cognitive ability to have these traits.

Eating animals kills more plants than eating plants.

If you actually believe plants are sentient and feel pain, then you will cause less plant pain by eating plants rather than animals. While this may seem counterintuitive, it is true, because animals are very inefficient at converting plant calories to animal calories. This inefficiency is in part because of the calories expended for metabolism as well as the calories and food that go into producing nonedible parts, such as bones, cartilage, feathers, fur, fins, skin, and organs.

As indicated by feed-conversion ratios, it takes twenty-five pounds of feed to produce one pound of beef, nine pounds of feed to produce one pound of pork, and five pounds of feed to produce one pound of chicken.3Professor Smil Vaclav. “Eating Meat: Evolution, Patterns, and Consequences.” Population and Development Review 28, no. 4 (2002): 599–639. http://home.cc.umanitoba.ca/~vsmil/pdf_pubs/PDR2003.pdf The total amount of plants consumed is far greater when you eat the animals that eat plants than when you eat plants directly.

There is no reason plants would experience pain.

Because pain is a response to avoid tissue damage by withdrawing or fleeing, and since plants have limited ability to withdraw or flee, there is no reason they would have evolved to feel pain.

Leonardo da Vinci realized this. In one of his notebooks, he said, “Though nature has given sensibility to pain to such living organisms as have the power of movement  in order thereby to preserve the members which in this movement are liable to diminish and be destroyed  the living organisms which have no power of movement do not have to encounter opposing objects, and plants consequently do not need to have a sensibility to pain, and so it comes about that if you break them they do not feel anguish in their members as do the animals.”4da Vinci, Leonardo. Leonardo Da Vinci’s Note-Books: Arranged and Rendered into English with Introductions. Empire State Book Company, 1908, 130

Some plants depend on being eaten for the survival of their species.

Some plants depend on being eaten to enhance the chances that their species will survive. The indigestible seeds of the plants will be spread over a wide geographical area as the plants are eaten by animals and then deposited in the animals’ excrement.

Visceral reactions differ with plants and animals.

At a less cerebral and more visceral level, I think we all sense the difference between pulling up a dandelion and slitting the throat of a chicken. Watching someone mow the lawn doesn’t evoke the same reaction as watching someone kick a dog.

Plants are sentient and intelligent only by the very broadest definitions.

Plants are sentient and intelligent only in a way similar to how bacteria and other single-cell organisms are sentient or intelligent. That is to say, plants generate and respond to chemical and electrical signals.

Outline

 Talking Points OutlineKnowledge Base
  • Context
    • This objection is not presented out of a concern for plant happiness but instead:
      • As an accusation of inconsistency.
        • “You don’t really care about all sentient beings, only animals.”
      • Implicitly as a reductio ad absurdum.
        • “So we can’t eat plants or animals now? We must eat something. Since plants and animals are both sentient, it doesn’t make any difference which we eat.”
    • Provocative clickbait titles do not engender credibility.
    • The “Extra” node of this outline presents two weaker arguments often used by advocates and explains why they are weak.
  • Plants differ from animals in ethically significant ways.
    • Plants cannot feel pain.
      • Plants lack a brain, a central nervous system, and pain receptors.
      • Plants may know they are being eaten via mechanoreceptors, but they don’t care.
        • According to Daniel Chamovitz, Dean of Life Sciences at Tel Aviv University:
          • Plants have nerve-cell pressure receptors (mechanoreceptors), not pain receptors (nociceptors).
          • “Plants can feel themselves being eaten  they just don’t have the capacity to give a shit.”
          • Source5Biologist “We Asked a Biologist If Plants Can Feel Pain.” Vice. Accessed July 26, 2017. https://www.vice.com/en_us/article/xd74nd/we-asked-a-botanist-how-sure-science-is-that-plants-cant-feel-pain-302
    • Plants cannot experience emotions.
      • Emotions are processed in the hippocampus and amygdala regions of the brain  neither of which are present in a plant.6Rand S. Swenson, M.D., Ph.D., “Review of Clinical and Functional Neuroscience.” Dartmouth Medical School, 2006. https://www.dartmouth.edu/~rswenson/NeuroSci/chapter_9.html
    • Plants have no self-awareness or sense of the future.
      • Thinking requires a brain, and without thought, there can be no self-awareness or sense of the future.
    • Plants do not have desires, preferences, or interests.
      • There is no evidence that plants have the cognitive ability to have these traits.
  • You kill many more plants by eating animal products than by eating plants.
    • Animals are inefficient at converting plants to edible animal matter.
      • This inefficiency is in part because of the calories expended for metabolism as well as the calories and food that go into producing nonedible parts, such as bones, cartilage, feathers, fur, fins, skin, and organs.
    • As indicated by feed-conversion ratios, it takes twenty-five pounds of feed to produce one pound of beef, nine pounds of feed to produce one pound of pork, and five pounds of feed to produce one pound of chicken.
      • Edible-food conversion ratios:
        • Chicken: 4.5 to 1
        • Pork: 9.4 to 1
        • Beef: 25.0 to 1
        • Carp: 2.3 to 1
        • Source7Professor Smil Vaclav. “Eating Meat: Evolution, Patterns, and Consequences.” Population and Development Review 28, no. 4 (2002): 599–639, http://home.cc.umanitoba.ca/~vsmil/pdf_pubs/PDR2003.pdf
        • Extra
          • Calculating feed-conversion ratios is fraught with complexity. A good discussion of the difficulties of calculation and the various ways these calculations can be performed is on the A Well-Fed World website at awfw.org/feed-ratios/.8
            “Animals Are Inefficient Converters of Food.” A Well-Fed World, October 26, 2015. http://awfw.org/feed-ratios 
  • There is no reason plants would experience pain.
    • Because pain is a response to avoid tissue damage by withdrawing or fleeing, and since plants have limited ability to withdraw or flee, there is no reason they would have evolved to feel pain.
    • Leonard da Vinci realized this. In one of his notebooks, he said, “Though nature has given sensibility to pain to such living organisms as have the power of movement  in order thereby to preserve the members which in this movement are liable to diminish and be destroyed  the living organisms which have no power of movement do not have to encounter opposing objects, and plants consequently do not need to have a sensibility to pain, and so it comes about that if you break them they do not feel anguish in their members as do the animals.”9da Vinci, Leonardo. Leonardo Da Vinci’s Note-Books: Arranged and Rendered into English with Introductions. Empire State Book Company, 1908, 130
  • Some plants depend on being eaten for the survival of their species.
    • Some plants depend on being eaten to enhance the chances that their species will survive. The indigestible seeds of the plants will be spread over a wide geographical area as the plants are eaten by animals and then deposited in the animals’ excrement.
  • At a visceral level, you know plants and animals are different.
    • We all sense the difference between pulling up a dandelion and slitting the throat of a chicken.
    • Watching someone mow the lawn doesn’t evoke the same reaction as watching someone kick a dog.
  • Plants are sentient and intelligent only by the very broadest definitions.
    • Plants are sentient only in a way similar to how bacteria and other single-cell organisms are sentient or intelligent.
    • That is, plants generate and respond to chemical and electrical signals.
  • Meta
    • Purpose
      • The purpose of this post is to present the reasons why the objection is not valid.
    • Contributors
      • Greg Fuller   Author
      • Isaac Nickerson   Copy Editor
    • Revisions
      • 2017-02-17 First published   glf
      • 2017-03-25 Reworded for clarity and to fix broken links   glf
      • 2017-07-25 Revised to better comply with newly published guidelines   glf
      • 2017-07-31 Changed structure to place most important points first   glf
      • 2017-08-08  Edited Workflow with Isaac’s copy edits   glf
      • 2017-08-21 Minor changes   glf
      • 2017-08-23 Copy editor’s pass   isn
      • 2017-11-27 Edited Leonardo da Vinci quote   isn
      • 2018-01-29 Added two talking points and table of contents
      • 2018-02-10 Copy editor’s second pass   isn
      • 2018-03-10  glf
        • Added an extra node to the outline to provide additional information on the complexity of calculating feed conversion ratios
        • Added a sentence to explain why animals are inefficient food sources
      • 2018-06-24 Edited most recent changes   isn

Clipboard

Quotes

As for stories that plants make sounds or ‘scream’ when cut, or can ‘sense’ when leaves are burned, they are 100 percent garbage. Lots of really bad research exists trying to ‘prove’ that plants can feel or think or communicate with humans or extraterrestrials. Such tales are pseudoscience, or even science fiction or urban legends. Lots of research on Plant perception (paranormal) has been done, including ideas that plants can sense when other creatures feel pain using ESP, but nothing in any peer-reviewed journals. Plant ESP was disproved by authors of a Science paper (and by the Mythbusters for what it’s worth). These are all moot points since, without nerves, nothing can feel pain. Plants are cool enough as they are: anthropomorphizing them is not necessary.   Matan Shelomi, Harvard Biologist10Matan Shelomi, Biologist. “Do Plants Feel Pain? – Quora.” Quora, March 22, 2016. https://www.quora.com/Do-plants-feel-pain

Explore

James McWilliams’s article “When Will We Stop Suggesting That Plants Have Feelings?”11James McWilliams. “When Will We Stop Suggesting That Plants Have Feelings?,” November 5, 2014. https://psmag.com/social-justice/will-stop-suggesting-plants-feelings-93768/ explores the topic as well as the motivations for such claims.

Footnotes   [ + ]

1.“We Asked a Biologist If Plants Can Feel Pain.” Vice. Accessed July 26, 2017. https://www.vice.com/en_us/article/xd74nd/we-asked-a-botanist-how-sure-science-is-that-plants-cant-feel-pain-302
2.Rand S. Swenson, M.D., Ph.D., “Review of Clinical and Functional Neuroscience.” Dartmouth Medical School, 2006. https://www.dartmouth.edu/~rswenson/NeuroSci/chapter_9.html
3.Professor Smil Vaclav. “Eating Meat: Evolution, Patterns, and Consequences.” Population and Development Review 28, no. 4 (2002): 599–639. http://home.cc.umanitoba.ca/~vsmil/pdf_pubs/PDR2003.pdf
4.da Vinci, Leonardo. Leonardo Da Vinci’s Note-Books: Arranged and Rendered into English with Introductions. Empire State Book Company, 1908, 130
5.Biologist “We Asked a Biologist If Plants Can Feel Pain.” Vice. Accessed July 26, 2017. https://www.vice.com/en_us/article/xd74nd/we-asked-a-botanist-how-sure-science-is-that-plants-cant-feel-pain-302
6.Rand S. Swenson, M.D., Ph.D., “Review of Clinical and Functional Neuroscience.” Dartmouth Medical School, 2006. https://www.dartmouth.edu/~rswenson/NeuroSci/chapter_9.html
7.Professor Smil Vaclav. “Eating Meat: Evolution, Patterns, and Consequences.” Population and Development Review 28, no. 4 (2002): 599–639, http://home.cc.umanitoba.ca/~vsmil/pdf_pubs/PDR2003.pdf
8.
“Animals Are Inefficient Converters of Food.” A Well-Fed World, October 26, 2015. http://awfw.org/feed-ratios 
9.da Vinci, Leonardo. Leonardo Da Vinci’s Note-Books: Arranged and Rendered into English with Introductions. Empire State Book Company, 1908, 130
10.Matan Shelomi, Biologist. “Do Plants Feel Pain? – Quora.” Quora, March 22, 2016. https://www.quora.com/Do-plants-feel-pain
11.James McWilliams. “When Will We Stop Suggesting That Plants Have Feelings?,” November 5, 2014. https://psmag.com/social-justice/will-stop-suggesting-plants-feelings-93768/