Underland

by Robert Macfarlane

  What this tracking revealed was astonishing. The carbon isotopes did not stay confined to the individual trees into which they were injected. Instead, they moved down the trees’ vascular systems to their root tips, where they passed into the fungal hyphae that wove with those tips. Once in the hyphae they travelled along the network to the root tips of another tree, where they entered the vascular system of that new tree. Along the way, the fungi drew off and metabolized some of the photosynthesized resources that were moving along their hyphae; this was their benefit from the mutualism.

  Here was proof that trees could move resources around between one another using the mycorrhizal network. The isotope tracking also demonstrated the unexpected intricacy of the interrelations. In a research plot thirty metres square, every single tree was connected to the fungal system, and some trees – the oldest – were connected to as many as forty-seven others. The results also solved the puzzle of the fir–birch mutualism: the Douglas firs were receiving more photosynthetic carbon from paper birches than they were transmitting. When paper birches were weeded out, the nutrient intake of the fir saplings was thus – counter-intuitively – reduced rather than increased, and so the firs weakened and died.

  The fungi and the trees had ‘forged their duality into a oneness, thereby making a forest’, wrote Simard in a bold summary of her findings. Instead of seeing trees as individual agents competing for resources, she proposed the forest as a ‘co-operative system’, in which trees ‘talk’ to one another, producing a collaborative intelligence she described as ‘forest wisdom’. Some older trees even ‘nurture’ smaller trees that they recognize as their ‘kin’, acting as ‘mothers’. Seen in the light of Simard’s research, the whole vision of a forest ecology shimmered and shifted – from a fierce free market to something more like a community with a socialist system of resource redistribution.

  Simard’s first major paper on the subject was published in Nature in 1997, and it was from there that the subterranean network of tree–fungus mutualism gained its durable nickname of ‘the wood wide web’. Her Nature paper was a groundbreaking publication, the implications of which were so significant that an entire research field subsequently formed to pursue them. Since then the scientific study of below-ground ecology has boomed. New technologies of detection and mapping have illuminated fresh details of this ‘social network’ of trees and plants. ‘The wood wide web has been mapped, traced, monitored and coaxed,’ as Simard puts it, ‘to reveal the beautiful structures and finely adapted languages of the forest network.’

  And among this new generation of the forest’s linguists and mappers is a young plant scientist called Merlin Sheldrake. Truly, that is his name.

  ~

  Merlin and I stand side by side in a beech coppice – the biggest I have ever seen, let alone entered. The stool is ten yards from one end to another, the tree perhaps 400 or 500 years old.

  ‘I’d guess this hasn’t been coppiced for at least half a century,’ I say to Merlin.

  Coppice shoots have grown, unlopped, into upright trunks, raying up around the edge of the coppice’s base and leaving a space in the centre easily big enough to hold us both. We stay there for a while, enjoying being inside this ancient tree, looking out at Epping Forest from between the grey-barked bars of our cage.

  Two of the beech’s lower limbs have melted into one another, their bark conjoining into a single continuous skin, their vascular systems growing and uniting. Living wood, left long enough, behaves as a slow-moving fluid. Like glacial ice – like the halite I had seen in Boulby, like the calcite I had seen in the Mendips, like stained glass in medieval churches which, over centuries, gradually thickens out at the base of each pane – living wood flows, given time.

  ‘I’ve heard this called “pleaching”,’ I say to Merlin, patting the fused branches. ‘The artist David Nash planted a circle of ash trees in a clearing in North Wales, then bent and wove the trees so that they grew not just next to one another but into one another, a dancing “Ash Dome”, made of a meld of boughs and limbs.’

  ‘Actually,’ says Merlin, ‘plant scientists have a technical term for this. We call it “snogging”, or to give it its full name, “tree snogging”.’ He smiles. ‘Well, not quite. The technical term is actually “inosculation”, from the Latin osculare, meaning “to kiss”. Inosculation means “to en-kiss”. It can happen across trees and between species too.’

  Though I know the word ‘inosculation’, I had not known its etymology; what seemed a chilly specialist term gains a passionate warmth, and feels true to this arboreal ‘en-kissing’, which makes it hard to say where one being ends and another begins. I think of Ovid’s version of the ‘Baucis and Philemon’ myth, in which an elderly couple are transformed into an intertwining oak and linden, each supporting the other in terms of both structure and sustenance, drawing strength for each other from the ground through their roots – and tenderly sharing that strength through their en-kissing.

  ‘This kind of merging happens below ground too,’ says Merlin, ‘but probably more intensely between the roots of the trees than between branches, because space is more limited below ground and the criss-crossing will be denser. And it happens vastly more profusely in the fungal networks, often between quite different species.’ He follows the pleaching of the two branches with a finger.

  ‘From being two hyphal tubes, two fungi are suddenly one, and things can start flowing between them, including genetic material and nuclei. This is why it’s so hard to deal with species concepts in fungi, or even the question of what an organism is – because while fungi do the sex thing, they also have this wildly promiscuous horizontal transfer of genetic material that is unpredictable in a still ill-understood way.’

  Merlin Sheldrake, as the oldest joke in mycology goes, is a fun guy to be around. During the days in which he conjures open the underland of Epping Forest for me, I ask more questions than I have of anyone for what feels like years. What he tells and shows me in that modest peri-urban forest reshapes my sense of the world in ways I am still processing.

  The night of Merlin’s birth was that of the Great Storm, 15 October 1987, when hurricane-force winds, gusting to strengths of 120 mph, capsized carriers, drove ferries ashore, and felled some 15 million trees – ripping up the forest floor across southern England and northern France and tilting it skywards in the form of root plates. The first full day of Merlin’s life was Black Friday, when the Dow Jones suffered a record fall, wiping trillions off global wealth and triggering a crash in financial markets worldwide.

  No, the omens of Merlin Sheldrake’s arrival into the world were not auspicious. In Greek myth he would surely have been fated to be a force for destruction and ruin. But he was given a magical name and he grew into a magical person. He is tall, slim, and very upright in his bearing. He has tight curls of dark hair, intense eyes with full circles of white visible around each iris, and a wide, warm grin. He is also a formidable scientist, with a doctorate in Plant Science from Cambridge. There is something faintly antiquarian to him – a disinterest in disciplinary boundaries, a boundless curiosity – and something of the heroic-age plant hunter too. He puts me in mind of a cross between Sir Thomas Browne and Frank Kingdon Ward, collector of Meconopsis betonicifolia, the legendary blue poppy of the Himalayas.

  It is typical of Merlin that he became fascinated from a young age not with the charismatic megafauna of the world, but instead with the undersung, underseen inhabitants of the biota: lichens, mosses and fungi. He studied them as an amateur teenage scientist, counting lichen species on gravestones and granite boulders, and trying to comprehend the subterranean architecture of fungal life – above-ground mushrooms as fruiting bodies that stand as mere fleeting allusions to immense underland structures.

  ‘My childhood superheroes weren’t Marvel characters,’ Merlin once said to me, ‘they were lichens and fungi. Fungi and lichen annihilate our categories of gender. They reshape our ideas of community and cooperation. They screw up
our hereditary model of evolutionary descent. They utterly liquidate our notions of time. Lichens can crumble rocks into dust with terrifying acids. Fungi can exude massively powerful enzymes outside their bodies that dissolve soil. They’re the biggest organisms in the world and among the oldest. They’re world-makers and world-breakers. What’s more superhero than that?’

  ~

  Merlin and I set off on foot into Epping Forest one morning from a high clearing, heading roughly north, keeping the sun to the right of our line.

  Epping extends to the north-east of London, and it is very far from a wildwood. It was first designated as a royal hunting forest in the twelfth century by Henry II, with penalties for poaching that included imprisonment and mutilation. Presently it is managed by the City of London Corporation, and has more than fifty bye-laws governing behaviour within its bounds – though the punishments are now fiscal rather than corporal. It is fully contained within the M25, the orbital motorway that encircles outer London. Minor roads traverse it, and it is never more than two and a half miles wide. Despite its small extent, Epping is easy to get lost in – a forest of forking paths to which, for a thousand years, the people of London and its surrounds have gone for shelter, sex, escape and a relic greenwood magic.

  Growl of roads. Whirr of a low-flying bumblebee, stirring the leaf litter with its downdraught. Buzzard overhead, turning, mewing. Old coppice trees left uncut, hydra-headed pollards. A fallen log, thick with moss; small orange fungi sprouting from wet breaks in its grain. Where trees thin out and light falls, hundreds of green beech seedlings are pushing up through the litter, none more than an inch high. Five fallow deer appear between hollies ahead of us, the dapple of leaf-light flicking off the dapple of their flanks as they move through the understorey.

  In the language of forestry and forest ecology, the ‘understorey’ is the name given to the life that exists between the forest floor and the tree canopy: the fungi, mosses, lichens, bushes and saplings that thrive and compete in this mid-zone. Metaphorically, though, the ‘understorey’ is also the sum of the entangled, ever-growing narratives, histories, ideas and words that interweave to give a wood or forest its diverse life in culture.

  ‘What interests me most,’ says Merlin, ‘is the understorey’s understory.’ He points around at the beech, the hornbeam, the chestnut. ‘All of these trees and bushes,’ he says, ‘are connected with one another below ground in ways we not only cannot see, but ways we have scarcely begun to understand.’

  While studying Natural Sciences at Cambridge, Merlin read Simard’s groundbreaking research into the wood wide web. He also read E. I. Newman’s classic 1988 paper, ‘Mycorrhizal Links between Plants: Their Functioning and Ecological Significance’. There Newman argued against the assumption that ‘plants are physiologically separate from each other’, proposing instead the existence of a ‘mycelial network’ that might link plants together. ‘If this phenomenon is widespread,’ wrote Newman, ‘it could have profound implications for the functioning of ecosystems.’

  Those ‘implications’ were indeed profound, and they fascinated Merlin. He already loved the alien realm of fungi. He knew that fungi could turn rocks to rubble, could move with swiftness both overground and underground, could reproduce horizontally, and digest food outside their bodies by means of metabolically ingenious excreted acids. He knew that their toxins could kill us, and their psychoactive chemicals could induce hallucinogenic states. The work of Simard and Newman, however, revealed to him that fungi could also allow plants to communicate with one another.

  Merlin was taught as an undergraduate by Oliver Rackham, the legendary botanist whose research transformed our understanding of both the cultural and botanical history of the English landscape. Working with Rackham, Merlin found himself most intellectually attracted to places where orthodox evolutionary theory felt thinnest – and for him the thinnest places were where mutualisms were at work. Mutualism is a subset of symbiosis in which there exists between organisms a prolonged relationship that is interdependent and reciprocally beneficial.

  ‘What fascinates me about mutualisms,’ says Merlin, ‘is that one would predict from basic evolutionary theory that they would be massively unstable, and collapse quickly into parasitism. But it turns out that there are very ancient mutualisms, which have remained stable for puzzlingly long times: between the yucca plant and yucca moths, for example, or of course between the bacteria that illuminate the bioluminescent headlamp of the bobtail squid, and the squid itself.’

  ‘Of course,’ I reply. ‘The ancient glowing-bobtail-squid-and-bacteria mutualism.’

  ‘The ultimate mutualism, though,’ says Merlin, ‘is between plants and mycorrhizal fungi.’

  ~

  The term ‘mycorrhiza’ is made from the Greek words for ‘fungus’ and ‘root’. It is itself a collaboration or entanglement; and as such a reminder of how language has its own sunken system of roots and hyphae, through which meaning is shared and traded.

  The relationship between mycorrhizal fungi and the plants they connect is ancient – around 450 million years old – and largely one of mutualism. In the case of the tree–fungi mutualism, the fungi siphon off carbon that has been produced in the form of glucose by the trees during photosynthesis, by means of chlorophyll that the fungi do not possess. In turn, the trees obtain nutrients such as phosphorus and nitrogen that the fungi have acquired from the soil through which they grow, by means of enzymes that the trees lack.

  The possibilities of the wood wide web far exceed this basic exchange of goods between plant and fungi, though. For the fungal network also allows plants to distribute resources between one another. Sugars, nitrogen and phosphorus can be shared between trees in a forest: a dying tree might divest its resources into the network to the benefit of the community, for example, or a struggling tree might be supported with extra resources by its neighbours.

  Even more remarkably, the network also allows plants to send immune-signalling compounds to one another. A plant under attack from aphids can indicate to a nearby plant via the network that it should up-regulate its defensive response before the aphids reach it. It has been known for some time that plants communicate above ground in comparable ways, by means of diffusible hormones. But such airborne warnings are imprecise in their destinations. When the compounds travel by fungal networks, both the source and recipient can be specified. Our growing comprehension of the forest network asks profound questions: about where species begin and end, about whether a forest might best be imagined as a superorganism, and about what ‘trading’, ‘sharing’ or even ‘friendship’ might mean between plants and, indeed, between humans.

  The anthropologist Anna Tsing likens the below-ground of a forest to ‘a busy social space’, where the interaction of millions of organisms ‘forms a cross-species world underground’. ‘Next time you walk through a forest,’ she writes memorably in an essay called ‘Arts of Inclusion, or How to Love a Mushroom’, ‘look down. A city lies under your feet.’

  ~

  Merlin and I have been walking the forest for two hours or so when we reach one of Epping’s great pollard beech groves. Pollarding – the pruning of the upper branches of a tree to promote dense growth – keeps trees alive for longer, indeed can enter them into an almost indefinite fairy-tale time of longevity. Here in the grove, long waving trunks yearn up to the sun. Through their leaves falls a green sub-sea light. It feels as if we are swimming through a kelp forest.

  We stop and lie down for a while on the woodland floor, on our backs, not speaking, watching the trees’ gentle movements in the breeze, and the light lacing and lancing from fifty feet or more above us. Where the pollards spread out to form the canopies, I realize I can trace patterns of space running along the edges of each tree’s canopy: the beautiful phenomenon known as ‘crown shyness’, whereby individual forest trees respect each other’s space, leaving slender running gaps between the end of one tree’s outermost leaves and the start of another’s.

&nb
sp; Lying there among the trees, despite a learned wariness towards anthropomorphism, I find it hard not to imagine these arboreal relations in terms of tenderness, generosity and even love: the respectful distance of their shy crowns, the kissing branches that have pleached with one another, the unseen connections forged by root and hyphae between seemingly distant trees. I remember something Louis de Bernières has written about a relationship that endured into old age: ‘we had roots that grew towards each other underground, and when all the pretty blossom had fallen from our branches we found that we were one tree and not two.’ As someone lucky to live in a long love, I recognize that gradual growing-towards and subterranean intertwining; the things that do not need to be said between us, the unspoken communication which can sometimes tilt troublingly towards silence, and the sharing of both happiness and pain. I think of good love as something that roots, not rots, over time, and of the hyphae that are weaving through the ground below me, reaching out through the soil in search of mergings. Theirs, too, seems to me then a version of love’s work.

  Merlin gets up, walks towards the centre of the grove as if looking for something, then bends down and brushes away leaf litter and beech mast, to clear a patch of soil the size of a saucer. I get up and follow him. He pinches some of the earth and rubs it between his fingers. It smears rather than crumbling: a rich, dark humus, made of composted leaves.

  ‘This is our problem when it comes to studying the fungal network,’ he says. ‘Soil is fantastically impenetrable to experiments, and the fungal hyphae are on the whole too thin to see with the naked eye. That’s the main reason it’s taken us so long to work out the wood wide web’s existence, and to discern what it’s doing.’

  Rivers of sap flow in the trees around us. If we were right now to lay a stethoscope to the bark of a birch or beech, we would hear the sap bubbling and crackling as it moves through the trunk.