Takeaways: The Light Eaters

I enjoyed reading The Light Eaters by Zoë Schlanger in part because of the sheer novelty of the research and the argument. The book presents fresh insights into how plants communicate, adapt, and thrive in ways that often go unnoticed. Schlanger’s exploration makes the hidden lives of plants feel incredibly dynamic and full of surprises.

1. In 1-2 sentences, what is the book about as a whole?

The Light Eaters by Zoë Schlanger aims to elevate the social status of plants on the species stack rank, arguing that their unique communication systems, memory, and adaptability mean they have agency. The book argues that plants possess a form of awareness that challenges conventional notions of intelligence and agency.

2. What are the 3-4 central questions it tries to answer?

• What does emerging research have to say about plant intelligence?
• Why is this new science so controversial?
• What’s the implication for science and society?

3. Summarize the answers in one paragraph each.

What does emerging research have to say about plant intelligence?

The complex behaviors exhibited by plants suggest a level of biological intelligence that challenges traditional views of awareness and adaptive agency. Unlike simple mechanical reactions, these responses are nuanced and adaptive, making plants appear far more sophisticated than we typically assume.

• Plants use sophisticated chemical signaling to interact with their environment, including releasing specific chemicals to attract beneficial organisms or deter predators. This signaling can occur through root networks connected by fungi, such as in the case of Douglas fir trees and paper birch, which share nutrients and send distress signals through these underground connections. Additionally, plants release chemicals like tannins or protease inhibitors to alter the taste or digestibility of their leaves, deterring herbivore attacks.
• Plants also use electrical impulses to respond to environmental stimuli, similar to how animals use nerve signals. For example, the sensitive plant (Mimosa pudica) uses electrical impulses to fold its leaves when touched, which helps deter herbivores. This allows plants to react to changes, such as physical damage or sudden movement, in a coordinated manner.
• Plant hearing: Research suggests that plants can detect sound vibrations. These include the buzzing of insects, the sound of water flowing, and even tiny popping noises produced by nearby roots. For example, when a plant detects vibrations from caterpillars chewing, it can increase the production of chemical defenses to deter further herbivore feeding. This ability, often called ‘plant hearing,’ helps them respond to environmental cues, like directing root growth towards a water source or increasing chemical defenses when they sense herbivores nearby.
• Kin recognition and social behavior: Studies indicate that plants can recognize their genetic relatives, a phenomenon known as kin recognition. When growing near kin, plants may alter their growth patterns to reduce competition and support each other, showcasing a form of social behavior. Interestingly, not all plants behave this way, suggesting variations in response that are akin to individual personalities. This cooperation includes sharing resources or allocating growth in a way that minimizes competition, highlighting an unexpected level of social interaction among plants.
• Mimicry and visual adaptation: There’s a wild plant, Boquila trifoliolata, that can imitate its neighbors’ leaves very closely. Some people think it might somehow be able to “see” its surroundings, while others believe this adaptation may be mediated by microbes. This mimicry demonstrates an extraordinary level of responsiveness, further challenging our assumptions about plant abilities.
• Schlanger highlights that plants possess a form of memory that allows them to “remember” past environmental changes, such as droughts or pest attacks. This memory can be seen not only within individual plants but also as inter-generational memory, where offspring inherit adaptations from their parent plants that help them better respond to similar stressors. This kind of memory-driven adaptation allows plants to improve their resilience and adaptability over time.

Why is this new science so controversial?

The concept of plant intelligence is controversial because it challenges long-standing definitions of consciousness and intelligence. Traditionally, intelligence has been defined based on characteristics like problem-solving, learning, and memory—traits typically linked to organisms with a brain or nervous system. The idea that plants, which lack these structures, can exhibit behaviors like learning, memory, and adaptive responses is met with skepticism in the scientific community. Critics argue that attributing intelligence or awareness to plants anthropomorphizes them, potentially distorting our understanding of these biological processes. Additionally, there is concern that overstating plant capabilities might lead to confusion about their true nature. However, proponents suggest that expanding the definition of intelligence could foster a deeper understanding of the diverse ways life adapts to and interacts with the environment. They argue that recognizing plant intelligence helps us appreciate the complexity of non-animal life and challenges the anthropocentric view that human-like traits are the only markers of true intelligence.

What’s the implication for science and society?

Recognizing plant intelligence could change how we see non-human life and make us rethink our relationship with nature. For example, understanding how plants communicate and adapt could lead to innovations in sustainable farming practices, such as optimizing plant interactions for better crop resilience, or more effective conservation strategies that take into account the complex social behaviors of plant ecosystems. This concept encourages us to appreciate biodiversity and the complexity of plant ecosystems more deeply. Over time, these ideas could influence fields like agriculture, conservation, and technology, leading to more sustainable practices and a respectful way of managing ecosystems. Though the practical impact might take time, recognizing plant intelligence could spark important changes in how we value and interact with the living world.

4. What are the most important things you have learned personally?

• I really geeked out on the sheer amount of new stuff I learned about plants.
• The research on how plants communicate and interact with their environment was incredibly eye-opening.
• I had no idea about all the chemical signaling mechanisms, like warning neighbors about pests or attacks using chemical cues, or the electrical signals that plants use across their bodies.
• Plants can hear! How rad is that? This isn’t the “play Mozart to make them grow” myth, but real experiments showing roots hearing water and growing towards it.
• They behave differently around their kin, pass down behaviors to their offspring, and selectively cooperate or compete by growing their stems, leaves, or roots in specific patterns.
• Then there’s Boquila trifoliolata, which can mimic its neighbors’ leaves so closely that real scientific theories include plant vision. Another theory, which I prefer, is that microbes play a role. Boquila can change the shape, size, color, and even vein patterns of its leaves to match those of the plant it climbs on, effectively allowing it to blend in and potentially evade herbivores.