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

by Zoë Schlanger

Any sense that immobility implies passivity is quickly banished by a look at plants’ vast capacity to make chemical weapons. Plants are themselves synthetic chemists, surpassing the best human technology in terms of the subtle complexity of the chemicals they can synthesize. A leaf, sensing that it has been nibbled, can produce a plume of airborne chemicals that tell a plant’s more distant branches to activate their immune systems, manufacturing yet more repellent chemicals to deter incoming aphids and other plant-eating bugs. Several species of plants have been found to identify a caterpillar’s species by sensing the compounds in its saliva, and then synthesize the exact compounds to summon its predator. Parasitic wasps then obligingly arrive to take care of the caterpillars. But Kaua‘i’s plants have none of these defenses, or in any case, far fewer. Any that the plants’ predecessors may have had—thorns, or poison, or repellent scents—were completely dropped after they landed on the island. No large land mammals, reptiles, or other potential predators made the journey from the mainland to the remote island chain. In fact, the only land mammal native to all of Hawai‘i is a small, fuzzy bat. (The journey its ancestor must have taken from North America is almost unthinkable; it likely gusted over inside a storm.) From the plants’ evolutionary perspective, there is no reason to spend energy on defenses when there are no predators to fend off, so mint has lost their mint oil, ...