Zoë Schlanger was a reporter covering climate change — a daily onslaught of floods, fires and other natural disasters — when she started wading into botany journals to relax.
There, she found something that surprised her: Researchers were debating whether plants might have an intelligence of their own.
Take corn, for example. It is one of several types of plants that can identify a caterpillar’s species by its saliva and send out plumes of chemical compounds into the air, summoning the insect’s predator. Alerted to the caterpillar’s presence by these compounds, a parasitic wasp arrives and destroys it, protecting the corn.
“One of the big debates is whether or not there’s any form of intention with plants and whether you need intention for something to have intelligence,” Schlanger said. “But one could argue that it doesn’t even matter if you can find intention in plants. What matters is watching what they actually do. And what they do is make decisions in real time and plan for the future.”
Schlanger spent the next several years exploring plant behavior for her book, “The Light Eaters,” which was published this month. On a recent walk through Central Park — past hydrangeas, hellebores, hyacinths and a Broadway softball league game between team “Hamilton” and team “The Lion King” — Schlanger described some of the astonishing things plants can do, and how learning more about them has informed her work reporting on climate change, which she now does for The Atlantic.
This interview has been edited and condensed for length and clarity.
What are some surprising things plants can do?
I am most drawn to the ways that plants manipulate animals to their benefit.
Yellow monkey flowers are able to lie to bees about how much pollen they have in their flowers to dupe them into showing up. Bees have this screening process where they’re sampling the volatile chemicals coming off the flowers, and those chemicals will indicate how much pollen is there for them. The monkey flowers have come up with a way to not have to go through the very expensive, energetic work of making all this pollen, but just emitting the volatile chemicals. The bee shows up and there is nothing there for it, but the flower gets pollinated anyway.
Or there’s the whole world of sexually deceptive orchids, which I think is so cool. There are some that grow one really unusual petal: this long strand, with a little bulb at the end of it. Male wasps will arrive and cling to it because it’s exuding almost the exact same pheromone as a female wasp.
I like it when they summon a predator. That’s just crazy.
Back in the ‘90s, researchers realized that corn and tomatoes were able to sample the saliva of the caterpillar eating them, and then synthesize chemicals that summon the exact parasitic wasp that would come and inject the caterpillars with their larva. So the wasp comes, puts loads of larvae inside of the caterpillars. The larvae hatch and eat the caterpillars from the inside out and then glue their cocoons to the outside of the caterpillar. So then you just have these husks of caterpillars, covered in wasp cocoons.
Ack!
Yeah, it’s a very creepy, bristly image. But the plant is trying to save itself. It’s eliminating a certain number of these caterpillars by summoning the exact predator to come destroy them. You can think of that as a plant using a tool. I mean, I don’t know about your feed, but mine is full of videos of things like crows using sticks as tools.
The algorithm has found you!
Absolutely. And obviously these crows are brilliant for doing that, but then what does it mean when plants are doing essentially the same thing, but to living organisms? They’re releasing chemicals that cause an animal to do something. Does that animal believe it’s doing this of its own free will? Is this a zombification of other animals, or is it more of a collaborative mutual exchange where the wasp gets something out of it? It’s hard to tell the difference between manipulation and collaboration in nature.
When scientists talk about “intelligence” in plants, what do they mean?
There are all of these calculations plants are constantly making by taking in every aspect of their environment and adjusting their lives accordingly, and it starts to look an awful lot like what we might consider intelligence — in a totally alien life form. That’s kind of how you have to treat it. Intelligence won’t show up in the way we expect ourselves to be intelligent. It’ll show up in ways that are evolutionarily appropriate for plants.
So no one is saying the plant is going to write a poem or do your math homework?
Not yet! Although researchers who study plant communication talk about syntax in plant communication and, in a way, sentence structure. But they’re talking about chemistry, chemical compounds floating in the air that have meaning.
What about the way plants sense the world? Do they interact with sound?
There’s some research happening now where scientists are playing tones for plants and realizing certain tones make plants produce more of certain compounds. There’s a tone that, if played for enough time, will make broccoli ramp up its antioxidants. In alfalfa sprouts, other tones will cause the plant to produce more vitamin C. One could see how — if they figured this out better — you could adjust the nutrition content of crops just by playing tones.
There’s also a whole world of playing tones to plants that causes them to produce more of their own pesticide, which is interesting when you think about how much pesticide we use to grow our food crops.
Have you changed your own behavior after spending so much time thinking about this? Do you have trouble eating salad now?
Obviously we’re animals that need to eat plants. There’s no way around that. But there is a way of imagining a future with agricultural practices and harvesting practices that are more tuned into the life style of the plant, the things it’s capable of and its proclivities.
This opens up the world of plant ethics. What does our world look like if we include plants in a moral imagination? There are lots of cultures that are already based on this. Robin Wall Kimmerer (author of “Braiding Sweetgrass”) writes a lot about this, how Indigenous science leaves a lot more room for questions about plants that are centered on respect and mutual interest.
What do you want people to take away from this book?
In thinking about plant intelligence, what we’re really thinking about is how much plants are active participants in their own life. They have some sense of agency, even if it doesn’t look anything like our own agency. I think that is really humbling. Everything wants to keep living. That has really helped me come back to climate reporting with more of a sense of what we stand to lose from climate change. Every single species is this ingenious biological feat that would be so foolish to extinguish.
