From Entangled Life. How Fungi Make Our Worlds,
Change Our Minds and Shape Our Futures, Merlin Sheldrake, 2020
From the Introduction
Fungal solutions don’t stop at human health. Radical fungal technologies can help us respond to some of the many problems that arise from ongoing environmental devastation. Antiviral compounds produced by fungal mycelium reduce colony collapse disorder in honeybees. Voracious fungal appetites can be deployed to break down pollutants, such as crude oil from oil spills, in a process known as mycoremediation. In mycofiltration, contaminated water is passed through mats of mycelium, which filter out heavy metals and break down toxins. In mycofabrication, building materials and textiles are grown out of mycelium and replace plastics and leather in many applications. Fungal melanins, the pigments produced by radio-tolerant fungi, are a promising new source of radiation-resistant biomaterials.
From chapter 7, Radical mycology
IN THE CARBONIFEROUS period, 290 to 360 million years ago, the earliest wood-producing plants spread across the tropics in swampy forests, supported by their mycorrhizal fungal partners. These forests grew and died, pulling huge quantities of carbon dioxide out of the atmosphere. And for tens of millions of years, much of this plant matter didn’t decompose. Layers of dead and un-rotted forest built up, storing so much carbon that atmospheric carbon dioxide levels crashed, and the planet entered a period of global cooling. Plants had caused the climate crisis, and plants were hit the hardest by it: Huge areas of tropical forest were wiped out in an extinction event known as the Carboniferous rainforest collapse. How had wood become a climate-change-inducing pollutant?
From a plant perspective wood was, and remains, a brilliant structural innovation. As plant life boomed, the jostle for light intensified, and plants grew taller to reach it. The taller they became, the greater their need for structural support. Wood was plants’ answer to this problem. Today, the wood of some three trillion trees—more than fifteen billion of which are cut down every year—accounts for about sixty percent of the total mass of every living organism on Earth, some three hundred gigatons of carbon.
Wood is a hybrid material. Cellulose—a feature of all plant cells, whether woody or not—is one of the ingredients and the most abundant polymer on earth. Lignin is another ingredient, and the second most abundant. Lignin is what makes wood wood. It is stronger than cellulose and more complex. Whereas cellulose is made up of orderly chains of glucose molecules, lignin is a haphazard matrix of molecular rings.
To this day, only a small number of organisms have worked out how to decompose lignin. By far the most prolific group are the white rot fungi—so-called because in decomposition they bleach wood a pale color. Most enzymes—biological catalysts that living organisms use to conduct chemical reactions—lock onto specific molecular shapes. Faced with lignin, this approach is hopeless; its chemical structure is too irregular. White rot fungi work around the problem using nonspecific enzymes that don’t depend on shape. These “peroxidases” release a torrent of highly reactive molecules, known as “free radicals,” which crack open lignin’s tightly bonded structure in a process known as “enzymatic combustion.”
Fungi are prodigious decomposers, but of their many biochemical achievements, one of the most impressive is this ability of white rot fungi to break down the lignin in wood. Based on their ability to release free radicals, the peroxidases produced by white rot fungi perform what is technically known as “radical chemistry.” “Radical” has it right. These enzymes have forever changed the way that carbon journeys through its earthly cycles. Today, fungal decomposition—much of it of woody plant matter—is one of the largest sources of carbon emissions, emitting about eighty-five gigatons of carbon to the atmosphere every year. In 2018, the combustion of fossil fuels by humans emitted around ten gigatons.
How did tens of millions of years’ worth of forest go un-rotted over the Carboniferous period? Opinions differ. Some point to climatic factors: Tropical forests were stagnant, waterlogged places. When trees died, they were submerged in anoxic swamps, where white rot fungi were unable to follow. Others suggest that when lignin first evolved in the early Carboniferous period, white rot fungi weren’t yet able to decompose it and required several million more years to upgrade their apparatus of decay.
So what happened to the vast areas of forest that didn’t decompose? It’s an inconceivably large amount of matter to pile up, kilometers deep.
The answer is coal. Human industrialization has been powered on these seams of un-rotted plant matter, somehow kept out of fungal reach. (If given the chance, many types of fungi readily decompose coal, and a species known as the “kerosene fungus” thrives in the fuel tanks of aircraft.) Coal provides a negative of fungal histories: It’s a record of fungal absence, of what fungi did not digest. Rarely since then has so much organic material escaped fungal attention.
I lay buried among white rot fungi for twenty minutes, slow-cooked by their radical chemistry. My skin seemed to dissolve into the heat, and I lost track of where my body started and stopped; a complex cuddle, blissful and unbearable in turn. No wonder coal can give off such heat: It is made from wood that hasn’t yet been burned. When we burn coal, we physically combust the material that fungi were unable to combust enzymatically. We thermally decompose what fungi were unable to decompose chemically.