As Jack C. Schultz puts it, plants “are just very slow animals.” Schultz is a professor in the Division of Plant Sciences at the University of Missouri in Columbia, and he has spent four decades investigating the interactions between plants and insects. “Plants fight for territory, seek out food, evade predators and trap prey. They are as alive as any animal, and – like animals – they exhibit behaviour,” says Schultz.
“To see this, you just need to make a fast movie of a growing plant – then it will behave like an animal,” adds Olivier Hamant, a plant scientist at the University of Lyon, France. Time-lapse camera reveals much of this, “as anyone who has seen the famous woodland sequence from David Attenborough’s Life series,” can attest.
So what is plant sense? Daniel Chamovitz of Tel Aviv University in Israel found that it isn’t all that different from our own. Chamovitz is the author of the 2012 book, What a Plant Knows, which “explores how plants experience the world by way of the most rigorous and up-to-date scientific research …” He distinguishes his book from earlier works like, The Secret Life of Plants, “a popular book published in 1973 that appealed to a generation raised on flower power, but contained little in the way of facts.” That work is now noted for supporting “the thoroughly discredited idea that plants respond positively to the sound of classical music.” But Chamovitz wasn’t trying to demonstrate that plants had feelings, instead, he was using contemporary scientific methods to ask “why, and indeed how, a plant senses its surroundings.”
And other researchers like Heidi Appel and Rex Cocroft are investigating plant hearing. They want to know why plants are affected by sound—not by classical music but by a predator’s approach. “In their experiments, Appel and Cocroft found that recordings of the munching noises produced by caterpillars caused plants to flood their leaves with chemical defenses designed to ward off attackers.” Plants respond to some sound with an ecologically relevant response.
Moreover Consuelo De Moraes, of the Swiss Federal Institute of Technology in Zürich, “has shown that as well as being able to hear approaching insects, some plants can either smell them, or else smell volatile signals released by neighboring plants in response to them.” Like us plants “smell or hear something and then act accordingly …” Of course, plants don’t have easily identifiable sense organs like human beings, and more research is needed to learn how they sense. Still, “the photoreceptors that plants use to “see” … are fairly well-studied.
The nutritional and environmental arguments for vegetarianism are quite strong. Vegetarians are healthier than meat-eaters, and the negative environmental impact of eating meat boggles the mind. (These claims are so uncontroversial that I won’t even footnote them, but they can be verified by a small amount of conscientious research.) If you want to be healthier don’t take vitamins, but forego animal products; if you want to help the environment, better to not eat meat than drive a Prius. (Driving a Prius will help too.)
But the moral argument traditionally rests on tremendous suffering animals experience when held captive under appalling conditions ameliorated only by their eventual slaughter, which itself we can assume is unpleasant. Animals suffer. But if plants also suffer what are we to eat? Must vegetarianism be rejected like meat-eating?
The first thing we might say is that if the choice is either plants or animals we still maintain that plants are less developed or organized forms of being and consciousness compared to what we usually call animals. Most importantly, plants don’t have brains, and their sensory experiences are more rudimentary—thus they probably suffer less. So, given the choice between eating either plants and animals, we should choose plants.
We also have the choice of eating food substitutes. Eventually, science should be able to mimic the nutritional benefits of so-called natural foods. Theoretically, we should be able to make even more nutritious food than was available in previous eras, or we may be able to redesign our bodies to run best on some nutritional goo! In fact, if we had robotic bodies, perhaps we could power them with our own solar panels.
For now, though I don’t think the fact that plants have sensory experiences changes that we should strongly prefer eating them to eating animal products. Eating plants is healthier, causes exponentially less environmental damage, and the sensory experiences of plants are not as rich as those of animals and thus plants suffer less. The argument for moral vegetarianism, therefore, remains intact.