While combing through science journals on her lunch break, climate journalist Zoë Schlanger came across a quiet revolution happening in the field of botany.
"When you hear scientists fighting with each other, you know that there's something going on in their field that's worth paying attention to," Schlanger said.
Those scientists were discussing whether plants could be considered intelligent — or possibly even conscious.
The contentious debate was stoked by recent scientific findings suggesting plants may have individual personalities, make complex decisions, and draw upon memories.
"These are all not things we think of as being part of the world of a brainless organism, and yet, plants were doing them all the same," Schlanger said.
Schlanger was enchanted, both by this group of botanists divided by the biggest philosophical questions of their field and by plants themselves. She spent the last five years in a deep love affair with plants, which she describes in her new book "The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth."
The book chronicles the latest revelations in plant intelligence and serves as an invitation for readers to reconsider the "invisible drama" of the green world around them.
Schlanger spoke with HPR's Savannah Harriman-Pote about the book. Schlanger is giving a talk at the University of Hawaiʻi on Sept. 15, as part of the Hawaiʻi Book & Music Festival.
Interview Highlights
On plants' ability to sense the world around them
ZOË SCHLANGER: Plants have this additional sense that we have, virtually none of which is the capacity to synthesize complex chemical compounds. Plants can sort of assess their environment with incredible attention to detail, things like moisture gradient and who their neighbors are according to the quality of light that passes through their neighbor's leaves and whatever the chemical composition of is of their world. And then, in their bodies, synthesize the exact chemical compound they need to get whatever they need to get done.
For example, plants will often lure insects to do their bidding. We see this in something as common as a tomato that might be in your garden. A tomato is able to sample the saliva that is coming off of the caterpillar eating it and use that chemical information to understand what species the caterpillar is, or at least what parasitic wasp they need to come pick off that caterpillar for them. And then they will make this compound, this combination of molecules, and release them through their pores, and that will float out on the air and reach the wasp. The wasp will know, "Okay, this is where I can come find the exact caterpillar I need in order to lay my eggs."
On research into whether plants have personalities
SCHLANGER: I went to a field site in Mammoth Lakes, California, where there's these beautiful fields of sagebrush, and I went there to meet a researcher named Richard Karban at UC Davis, and he's studying the possibility that plants might have consistent personalities that maintain themselves throughout their lifetimes and he's using animal behavior research to ask these questions of plants. Normally, when we think about animal personalities, it's tested on a sort of shyness-to-boldness continuum. You have kind of your scaredy-cat animals and your very brave animals. And Richard Karban wanted to apply this to his sagebrush because he knew exactly the chemical composition and frequency of their alarm calls.
So plants are able to emit these compounds, these chemical compounds that are that alert plants nearby to the presence of danger. And he had noticed that some sagebrush would let out alarm calls, at the slightest disturbance. They'd constantly pump out these compounds that say, "We're in danger over here." Other plants would only pump these compounds out when the danger was truly very high, when there was truly a lot of pests eating them, and he found that actually, it's true that these plants maintain that sort of personality trait throughout their lifetimes, and other plants appear to be able to tell who's who.
He saw that sagebrush were more likely to activate their own defense systems when they got a signal from the bolder sagebrush and would sort of ignore the more scaredy-cat sagebrush, who occupied this "Boy Who Cried Wolf" place in their little plant society.
On the Kauaʻi botanist who taught her how to feel for plants
SCHLANGER: Steve Perlman was one of the people that first brought me into this world of incredible reverence for plants. I was able to meet him while he was doing fieldwork on the Nāpali cliffs where he had previously single-handedly saved multiple species there. Steve had spent his career doing things like hopping out of helicopters and rappelling down these cliffs to reach plants that had as few as five individuals left. They were the most extremely endangered plants, and he would lovingly hand-pollinate these plants. And he had such a profound relationship to some of these plants.
He described to me the experience of sitting with the last individual of its species and watching it die. He had not been successful in saving it, which is the case for a lot of plants. And he described writing poetry for plants, bringing the last specimen of a species to a bar and toasting its life. To him, you don't save species just because they're useful to humans. You save species because they themselves have a right to exist. He really introduced me to what it meant to really feel for a plant.
On how people can overcome 'plant blindness'
SCHLANGER: The National Tropical Botanical Garden is an incredible place on Hawaiʻi that has a presence in all the islands, and I learned so much from them while I was there. One way to sort of regain this intimacy and start to see plants as individuals and understand their individual lifestyles is just to start learning their names.
Once you start to learn the individual names of the plants that you live with every day, that are all around you, and then you can go one step further. What are their lifestyles? But really, I think starting with naming, getting an identification book, taking a class at your local botanical garden, finding your nearest naturalist. This does not have to be a hyper-professional pursuit. There are so many people in all of our communities that have deep knowledge of plants, maybe just by having a garden, and spending time with people like that can be a wonderful gateway into relieving some of that plant blindness.
On her favorite plant fact to share at parties
SCHLANGER: I love thinking about the fact that primrose flowers, which are these perfect cup-shaped, lemon-yellow flowers that grow close to the ground, a researcher recently discovered that those plants will sweeten their nectar by three times just in response to the sound of a bee buzzing.
Just when they can "hear" their pollinator nearby, they will sweeten their nectar. And that researcher plucked off a few petals to see if the effect would change, and found that the bee-buzzing sound no longer had that effect, which suggests that those plants' bowl-shaped flowers are that shape specifically to take on the vibration of the bee-buzzing, much the same way as a satellite dish is concave. And that researcher says that now when she sees a flat field of flowers, she sees a field of ears, which I love.
