Underland: A Deep Time Journey

by Robert Macfarlane

‘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. ‘You can put rhizotrons into the ground to look at root growth,’ Merlin says, ‘but those don’t really give you the fungi because they’re too fine. You can do below-ground laser scanning but, again, that’s too crude for the fungal networks.’ I am reminded once more of how resistant the underland remains to our usual forms of seeing; how it still hides so much from us, even in our age of hyper-visibility and ultra-scrutiny. Just a few inches of soil is enough to keep startling secrets, hold astonishing cargo: an eighth of the world’s total biomass comprises bacteria that live below ground, and a further quarter is of fungal origin. ‘We know the network is there,’ Merlin says, ‘but it’s so effortful to track it. So we have to look for clues to the labyrinth – find clever means of following its paths.’ I kneel beside him. I can see dozens of insects just in this small area, the names of most of which I do not know: gleaming spiders and red-bronze beetles battling over...