The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth

“Plants, after all, are their own clade of life, with an evolutionary history that swerved away from our own long ago. Painting them with our concepts of intelligence and consciousness does a disservice to their essential plantness.”

Schlanger continuously wrestles with is whether it is right to draw comparisons between human and plant life. Here, she suggests that doing so does a disservice to plants and prevents scientists from considering the full breadth of what plants can do. By imposing human qualities on plants, scientists run the risk of overlooking how plant experiences and behaviors diverge from that of humans.

“The experience of flashes of the eternal, the real, the gestalt, runs like a threat throughout naturalist literature.”

This quotation exemplifies how Schlanger blends philosophy, science, and spiritualism in her study of plants. She suggests that plants have much to reveal to humans—both rationally through science and mystically through an emphasis on the collective whole and the interconnectedness of all beings.

“Aristotle stripped plants of even the earlier ability to desire or sense; they existed wholly as instruments of man.”

In Chapter 2, Schlanger questions how the field of botany might be different if Aristotle’s Ladder of Life was not so prominent in scientific classification. She suggests that if Western thinkers embraced The Complexity of Ecology over human centrism, then many of the challenges humans face with climate change might have radically different outcomes.

“Right now, one camp of botanists is arguing that it’s absolutely time to expand our notions of consciousness and intelligence to include plants, while another argues that’s an illogical road to go down. Many more botanists are sitting in the middle, quietly doing remarkable work…I’ve been sitting with them.”

Schlanger’s work highlights the controversial arguments for and against plant intelligence. In this passage, Schlanger suggests she is taking an unbiased approach to the topic, exploring what both camps have to offer. However, Schlanger repeatedly uses language that polarizes the scientific community—words like “communication” and “awareness”—to describe plant behavior.

“Communication implies a recognition of self and what lies beyond it—the existence of other selves. Communication is the forming of threads between individuals.”

This quotation emphasizes the controversy surrounding the language used in Schlanger’s work. The term “communication” suggests plants make intentional decisions about the types of information they spread and with whom they share it. Some used this theory about intentional decision-making in plants as an argument for Plant Consciousness.

“The answer, Rhoades discovered, was improbable, remarkable, and dangerous: the trees were communicating with each other. Trees the caterpillars hadn’t yet reached were ready; they’d turned their leaves into weapons.”

In Chapter 3, Schlanger points to a specific piece of scientific research that revealed that trees spread sensiochemical messages about predators. In response to caterpillars, trees on Rhoades’s campus altered their chemical makeup by increasing the tannins in their leaves. This act exemplifies The Constant Motion of Biological Creativity and the swiftness with which plants can adapt to their environments.

“Intention poses the hardest of problems, because it cannot be directly discovered.”

While communication implies intention, it is difficult to measure exactly what is behind the decision-making of plants. Some scientists argue that plants’ ability to alter their chemical compounds indicates an evolutionarily ingrained system of defense. Others argue it reveals that plants are sensing, remembering, and making intentional choices.

“Electricity is entangled in every aspect of our living. It is behind our ability to move, think, breathe. It doesn’t have a pulse, but a pulse has it; or, rather, electricity is the reason for the pulse at all.”

In another argument for Plant Consciousness, electrical waves in plants are said to mirror the electrical waves in human brains. Here, Schlanger correlates humans and plants once more, indicating that electricity is the force behind human consciousness.

“Plants are fully aware of our contact with them, and will rearrange their lives to respond to such treatment.”

Schlanger’s use of the word “aware” in this passage contributes to her thesis for plant consciousness. This sentence emphasizes intentionality and the recognition of both the self and others, indicators that philosophy often uses to make sense of human intelligence and conscious experience.

“Plants have designed the world around them to suit their needs. Why don’t we get that? We couldn’t be here were it not for them. The idea that they lack agency is absurd, once you have that awareness.”

Schlanger cites a conversation with researcher Simon Gilroy, who advocates for plant agency. The term “agency” emerges throughout the work as scientists wrestle with plant decision-making. The term connects two themes: Plant Consciousness and The Constant Motion of Biological Creativity. By asserting that plants have agency, researchers like Gilroy suggest plants have both awareness and the ability to make decisions that impact their lives and environments.

“The words scientists use are important, because what they’re working with is complex; using mushy words like thinking or communicating just confuses things.”

This quotation offers another example of scientific contradiction and Schlanger’s exploration of the rift in the botanical community. While acknowledging that words like “thinking” draw a correlation between humans and plants, she also titles chapters with and utilizes these terms in her own argumentation.

“As we have seen, some plants will pump out bitter tannins in a bid to taste disgusting. Others will manufacture their own insect repellant.”

Sensiochemicals provide a striking example of The Constant Motion of Biological Creativity. Research suggests that plants can chemically respond to predators and environmental factors within milliseconds, which reveals their quick and creative problem-solving abilities.

“What would it mean if a plant could remember? Not the genetic sort of memory, of birds returning to the same migratory grounds each year, but individual memory. Elastic memory. Memories that change when circumstances do.”

Chapter 6 explores another argument for Plant Consciousness: plant memory. Traditional views of plant memory position it in the context of evolutionary processes. Plants have circadian memory because of their own internal mechanisms, which are devoid of decision-making. However, Schlanger points to research that suggests plants have more complex memories that allow them to make decisions based on complex systems of communication.

“Memory has long been tangled up with how we think of our own consciousness. Our ‘sense of pastness,’ as it is sometimes called, fills out the awareness of ourselves as beings who move through time.”

Once again, Schlanger correlates plant consciousness with human consciousness, suggesting that the ability to hold memory and make informed decisions based on memories is evidence of a plant’s intelligence. By asserting that plants are conscious, Schlanger establishes a framework for the theme The Complexity of Ecology. If plants can remember and make choices based on what they remember, they hold a greater awareness of their own position in a larger network.

“Dodders are wonderfully fun for watching a plant make a choice: they prefer tomatoes to wheat, for example.”

Schlanger describes a parasitic plant with no leaves that probes the air for a host. Her language in this passage—“choice” and “prefer”—emphasizes the dodder’s intention and agency to make decisions through sensory experience and intelligence.

“Interspecies chatter of this sort is constant and entirely invisible to human perception. The communication is sophisticated, dynamic, multilayered, and quick—all of this happens in a matter of mere moments.”

Schlanger widens the scope of her research into The Complexity of Ecology, looking at how plants interact with other species. She describes how walking through the woods refines ecological understanding because it allows her to see how different species interact to form a complex and collective whole.

“He knew that certain orchids only attracted certain species of wasps, so the chemistry must be rather specific. He figured they had to be using some combination of the more than 1,700 floral scent compounds already known.”

Schlanger points to research into orchids as an example of The Constant Motion of Biological Creativity. Orchid flowers are designed to mimic the bodies of female wasps and entice male wasps to roll around in their pollen. However, orchids do more than visually mimic female wasps: They also release extraordinarily complex and precise chemical compounds designed to trick male wasps into thinking the bud is a female wasp.

“A Peruvian ecologist named Ernesto Gianoli had discovered that a common vine in this rain forest was capable of something no other plant was known to do. It could, quite spontaneously, morph into the shape of almost any plant it grew beside.”

The boquila vine mimics other plants to keep predators from munching on its leaves. Scientists have yet to discover exactly how the vine alters its leaves to match a variety of species, including ferns and the spiky leaves of some plants. For Schlanger, the boquila vine embodies Plant Consciousness and plants’ ability to make informed decisions about their surroundings.

“As we learn more about the integration between our health and our microbes, they begin to seem more indistinguishable from what we conceive of as ourselves. We are not our microbiomes, but we certainly aren’t ourselves without them.”

Schlanger emphasizes the complexity of ecology by revealing how microbiomes interact with plants and humans. The line between the individual and the collective becomes blurred; one cannot exist without the other. This argument connects Schlanger’s work as a climate reporter to her exploration into botany. By championing the collective over the individual, humans may be able to reverse the effects of climate change, a consequence of humanity positioning itself above ecological systems.

“Research has found that teams of people perform better when their brain waves are synchronized, that copilots’ brains tend to synchronize during takeoff and landing when collaboration is crucial, and that people are cognitively in sync report higher feelings of cooperativeness and affinity for each other.”

Schlanger connects Plant Consciousness with The Complexity of Ecology, suggesting that plants continually experience a form of consciousness that mirrors the human experience of synchronized brain waves. The positive impact of this synchronization reflects the benefits of an ecological approach.

“The implication of kin recognition is that plants have a social life. They are aware of who they are in the company of, and decide how to behave toward them accordingly.”

Schlanger explores the social lives of plants to strengthen the case for Plant Consciousness. Plants’ ability to distinguish their own species from others and their relatives from other plants of the same species suggests they have highly complex social lives. Schlanger highlights philosophical theories that frame consciousness as the recognition of the self and others to further bolster her argument.

“Competition isn’t actually all that important. It’s surely one driver of change, but it’s only one in a profusion of drivers. Plant cultures are multifactorial, like human cultures.”

Focusing on The Complexity of Ecology challenges traditional thinking about evolutionary competition. If plants knowingly participate in an ecological way of life, elevating the collective over the individual, this suggests they do not always prioritize their own survival.

“All biology, I began to understand, is in fact ecology.”

Schlanger argues that ecology is the driving force behind plant life and even all life. By focusing on ecology over individualism, humans could gain a more comprehensive understanding of life and the way natural systems work both in harmony and discord with one another.