Is it ethical to eat plants? The argument against using animals for food has been gaining a lot of ground these days; veganism is becoming way more prominent, and there have been several bestselling books making the case against eating meat. But a few months ago I started wondering about about plants, and whether the logic could be extended to them.

The idea seems absurd on the surface. Anti-meat advocates point out that animals are conscious, have agency, and often have astonishingly high levels of awareness, intelligence and society. (Grey parrots and pigs are extremely smart; octopuses are almost alarmingly so.) But surely the same can’t be said of plants, can it?

Apparently it can. In a recent story in the New York Times, Natalie Angier — a science writer and (self-admittedly) irregular vegetarian — makes the case that plants “no more aspire to being stir-fried in a wok than a hog aspires to being peppercorn-studded in my Christmas clay pot … Plants are lively and seek to keep it that way.”

The most fascinating part for me was Angier’s description of the way plants recognize they’re being eaten, and fight back by calling for help:

Just because we humans can’t hear them doesn’t mean plants don’t howl. Some of the compounds that plants generate in response to insect mastication — their feedback, you might say — are volatile chemicals that serve as cries for help. Such airborne alarm calls have been shown to attract both large predatory insects like dragon flies, which delight in caterpillar meat, and tiny parasitic insects, which can infect a caterpillar and destroy it from within. [snip]

… certain plants can sense when insect eggs have been deposited on their leaves and will act immediately to rid themselves of the incubating menace. They may sprout carpets of tumorlike neoplasms to knock the eggs off, or secrete ovicides to kill them, or sound the S O S. Reporting in The Proceedings of the National Academy of Sciences, Dr. Hilker and her coworkers determined that when a female cabbage butterfly lays her eggs on a brussels sprout plant and attaches her treasures to the leaves with tiny dabs of glue, the vigilant vegetable detects the presence of a simple additive in the glue, benzyl cyanide. Cued by the additive, the plant swiftly alters the chemistry of its leaf surface to beckon female parasitic wasps. Spying the anchored bounty, the female wasps in turn inject their eggs inside, the gestating wasps feed on the gestating butterflies, and the plant’s problem is solved.

You could counterargue, of course, that the plants aren’t actually conscious or self-aware. But you could make the same argument about some animals. And of course, we have legal arguments all the time about the pulling the plug on mentally incapacitated humans. (Granted, we’re not pulling the plug on them for the purposes of farming and eating them, but some of the philosphical nut is there.) The point is, we’ve always drawn a very clear line between animals and plants; Angier thinks it ought to be much blurrier.

The funny thing is, in practice we do have many situations where people ascribe a lot of agency to plants, and get enormously upset when those plants come to harm. Trees are a good example: There are laws in many townships prohibiting you from cutting down older trees, and I’ve seen people weep when a favorite tree is felled by a storm. You can’t judge the moral status of a being based merely on whether its demise upsets somebody — but the emotions stirred here are interesting and suggestive, to say the least.

By the way, the comment thread for Angier’s article is sprawling and super interesting too.

(The picture of the brussels-sprout plant above is courtesy arnold | inuyaki’s Creative-Commons-licensed Flickr photostream!)