This is one of the most exciting books I’ve read, and if anyone had told my fifteen year old self that one day I’d be extolling the virtues of fungi and have thought them mad. Mushrooms on toast were nice and that was it.
But within two pages of this book, I was hooked by mind-bending concepts. Plants would never have existed without fungi, the earliest plant prototype – algae only making it out of water 500 million years ago via the fusion/collaboration with fungi which served as their root systems for millions of years until plants evolved their own. The fungi didn’t go away. Plants still depend on mycorrhizal fungi as root extensions, but more about that later.
But even before 500 million years ago— before the age of the dinosaurs—you had Prototaxites – living spires taller than two storey buildings, dotting the landscape and the home to insects chewing out rooms and corridors. This was before animals with backbones had moved out of the water and were the largest living structures on land for at least 40 million years— 20 times longer than our species has existed. Puts the pyramids, climate change and Afghanistan into perspective.
Fungi holds the soil together and weave themselves through the gaps between plant cells in an intimate brocade and help defend them against disease—though they can also cause it. Most fungi form networks of many cells known as Hyphae, fine tubular structures that branch, fuse and tangle into the anarchic tangle of mycelium. Water and nutrients flow through and within the mycelium networks. The mycelium of some fungal species is electrically excitable and conducts waves of electrical activity along hyphae analogous to the electrical impulse in animal nerve cells.
Slime is not strictly fungi but like fungi and other so called ‘brainless’ organisms – a great problem solver.
Slime, or Physarum are easy to study and reveal exploratory networks made of tentacle like veins. They have no central nervous system – or anything that resembles one. And yet they can make decisions by comparing a range of possible courses of action and can take the shortest path between two points in a labyrinth. Japanese researchers released slime moulds into petri dishes modelled on the Greater Tokyo area. Oat flakes marked major urban hubs and bright lights represented obstacles eg mountains – slime mould abhors light. After a day, the slime mould had found the most efficient route between the oats creating a network almost identical to the Tokyo rail system – the American road System – Ancient roman roads in central Europe – even IKEA.
Because these organisms don’t look like us or have brains, they are placed on the very bottom rung of the chain of intelligent life. And yet they can solve problems, communicate, make decisions, learn, and remember—maybe pick up the odd GCSE.
For Sheldrake, Mycelium is the ecological connective tissue, the living seam by which much of the world is stitched in relation to everything else. Observed in laboratory conditions, it spreads radially in every direction forming a fuzzy white circle. Eventually the growing circle encounters a new block of wood. Only a small part of the body touched the wood, but the behaviour of the entire network changes. The mycelium stopped exploring in all directions. It withdrew the exploratory tips and thickened the connection with the newly discovered block. In the laboratory, the Tokyo experiment was re-enacted, using mycelium rather than slime – a soil sculpture of Britain with blocks of wood representing towns and cities. Pretty soon she had a facsimile of the motorway network.
And all of this is going on in the soil connecting trees and plants, insects and mammals.
He also makes claims I find hard to believe and yet, then again, I'm a man of faith, even when Sheldrake claims that: 'In one teaspoon of healthy soil there are hundreds of thousands of metres of fungal mycelium, more bacteria, protists, insects and arthropods than the number of humans who ever lived on Earth.' A trowel maybe. But zooming in on my iPhone reveals nothing. 😃
Sheldrake draws the analogy between people and plants. When connections are made between people, networks emerge. Fungal networks make connections between plants but with one crucial difference. It’s not a matter of having 20 acquaintances but having 20 acquaintances sharing a common circulatory system.
He waxes lyrical on Mycorrhizal fungi prioritising, problem-solving, withdrawing or pushing resource distribution. Plants that share a network, he argues, grow more quickly and survive better than neighbouring plants that are excluded from the common network.
Fungal networks provide highways for bacteria to migrate around the obstacle course of the soil. When broad-bean plants are attacked by aphids they release volatile compounds drifting out from the wound that attract predatory wasps. Sheldrake suggests the release of these info-chemicals are synchronised by fungal networks in the soil. Other examples include tomatoes attacked by caterpillars and pine under attack from budworm.
He asks the question: why should a single plant ‘scream’ when under attack by aphids? Is it a response without purpose or to warn its neighbouring plants, but then why would plants evolve to be altruistic?
The answer for Sheldrake is the unobserved fungus sharing the positives and negatives of neighbouring plants. If a whole clump of plants moves into a state of high alert they will emit a larger plume of wasp-summoning chemicals than a lone plant can. Any fungus that can magnify the chemical beacon will benefit from this ability along with the plant. Similarly, when stress signals pass from a sick plant to a healthy plant, it is the fungus that stands to benefit from keeping the healthy plant. Walk in a forest and you tread a hidden world. Beneath your feet fungal networks are busy sharing resources between healthy trees and those not doing so well.
Prince Charles got a lot of stick in the 1970’s for ‘talking to trees.’ It has now become both accepted and reasonably fashionable. I’ve been known to stroke them on occasion. But is the world ready for ‘fungi whisperers’ ageing hippies, their lips pressed close to the soil? Maybe it should since we carry more microbes than cells and have been on this earth a mere blink in comparison.