Like many small organisms, fungi are often overlooked, but their planetary significance is outsize. Plants managed to leave water and grow on land only because of their collaboration with fungi, which acted as their root systems for millions of years. Even today, roughly 90 percent of plants and nearly all the world’s trees depend on fungi, which supply crucial minerals by breaking down rock and other substances. They can also be a scourge, eradicating forests — Dutch elm disease and chestnut blight are fungi — and killing humans. (Romans used to pray to Robigus, the god of mildew, to guard their crops against plagues.) At times, they even seem to think. When Japanese researchers released slime molds into mazes modeled on Tokyo’s streets, the molds found the most efficient route between the city’s urban hubs in a day, instinctively recreating a set of paths almost identical to the existing rail network. When put in a miniature floor map of Ikea, they quickly found the shortest route to the exit.
“Entangled Life” is full of these sorts of details, but it’s also deeply philosophical: a living argument for interdependence. Without fungi, matter wouldn’t decay; the planet would be buried under layers of dead and unrotted trees and vegetation. If we had a fungi-specific X-ray vision, we would see, Sheldrake writes, “sprawling interlaced webs” strung along coral reefs in the ocean and twining intimately within “plant and animal bodies both alive and dead, rubbish dumps, carpets, floorboards, old books in libraries, specks of house dust and in canvases of old master paintings hanging in museums.”
The idea of fungi as metaphor for life has lately entered the zeitgeist, seeded in part by the forest scientist Suzanne Simard, who discovered that trees are connected through a mycelial network, the “Wood-Wide Web.” There