Previously, I thought this common “argument” against veganism was a joke. A throwaway, tongue-in-cheek comment made to trivialise the concept of veganism. However, on closer inspection it appears that some people are genuinely arguing that plants and non-human animals have a similar moral standing when it comes to killing them for food.
Every now and then, a newspaper or magazine article does the rounds on social media, gleefully shared by people who have a strange obsession in portraying vegans and vegetarians as hypocrites. These articles often cherry-pick findings from actual scientific studies which show certain capabilities of plants, in order to argue that avoiding eating animals in favour of plants for ethical reasons is pointless.
As a scientist, I find the studies themselves fascinating, some of the adaptations plants have evolved are really quite amazing. Unfortunately, the way these studies are reported in the media can be quite biased, drawing conclusions from the research that the original authors never mentioned.
“Plant can hear themselves being eaten”
An oft referenced study is one that was undertaken at the University of Missouri (Appel and Cocroft, 2014 ). This study found that a certain species of plant released defence chemicals (which made it less attractive to herbivores) in response to the sound of caterpillars munching on it (in order to deter them from munching further!).
The Sun article claimed that plants “know” when they are about to be eaten, and are “not happy” about it. Business Insider news website also published an article on this study, opening “vegetarians and vegans pay heed”, before going onto say that plants “don’t like it” when they are eaten. The scientific study which these assumptions have been drawn from, predictably, makes no such claims suggesting plant consciousness or sentience.
One of the researchers who conducted the study, Dr Heidi Appel, summarised their findings as follows; “We found that feeding vibrations signal changes in the plant cells’ metabolism, creating more defensive chemicals that can repel attacks from caterpillars”.
Can plants feel pain?
Our current understanding of pain involves sensory and emotional, subjective components. Analogous neurological structures (for example, specialised pain receptors, also called nociceptors) are found in both human and non-human animals .
Studies have also shown that animals are likely to experience the emotional, subjective components of pain (see my previous article on this topic). Plants, however, do not have such analogous structures, and there is no scientific evidence to show that they can “feel” in the same way as humans and other animals can.
Professor Daniel Chamovitz, Dean of the Faculty of Life Sciences at Tel Aviv University, is a plant scientist who had conducted extensive research into how plants experience the world, and has even written a popular book on the topic. Although Chamovitz often talks about plant feelings, he acknowledges that “a plant can’t suffer subjective pain in the absence of a brain, I also don’t think that it thinks” .
Science is always evolving and advancing (that’s part of what makes it so great!), so it may be the case that in years to come we find out that plants are sentient in their own way, and if that day comes we will seriously have to think about how we treat them.
However, in terms of our current scientific understanding, there are clear differences between plants and animals. When it comes down to it, almost no one truly believes that harming plants and animals is the same, this cartoon from Vegan Sidekick demonstrates this quite well:
Even if, in an unlikely future scenario, plants are found to have “feelings” similar to animals, veganism would probably still be the most compassionate diet: It is estimated that “for every 1 kg of high-quality animal protein produced, livestock are fed about 6 kg of plant protein” . If this is the case then many more plants are killed to feed an animal up to slaughter weight, and then kill and eat the animal, than to just kill and eat the plants ourselves.
 Appel, H.M. & Cocroft, R.B. (2014) Plants respond to leaf vibrations caused by insect herbivore chewing. Oecologia 175: 1257. doi:10.1007/s00442-014-2995-6
 National Research Council (US) Committee on Recognition and Alleviation of Pain in Laboratory Animals. National Academies Press 2009 (link)
 Interview with Professor Chamovitz, Published on The Scientific American website (accessed 19/06/2017) (link).
 Pimentel, D. & Pimentel, M. (2003) Sustainability of meat-based and plant-based diets and the environment. The American Journal of Clinical Nutrition 78 (3): 660-663. (link)