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December 26, 2022 - January 29, 2023
A study published in 2018 by researchers at the University of British Columbia found that the speed of tree migration may indeed depend on their mycorrhizal proclivity.
As the Laurentide Ice Sheet retreated, the species that migrated faster were the more promiscuous ones, those that stood a better chance of meeting a compatible fungus when they arrived somewhere new.
The fungi that live in plant leaves and shoots – known as ‘endophytes’ – can have similarly dramatic effects on a plant’s ability to make a life in a new place.
Fungi can determine which plants grow where; they can even drive the evolution of new species by isolating plant populations from one another.
One species, the Belmore sentry palm (Howea belmoreana), grows on acidic volcanic soils, while its sister species, the Kentia palm (Howea forsteriana), lives on alkaline chalky soils.
‘involution’ – from the word ‘involve’ – better describes this tendency: a ‘rolling, curling, turning inwards’.
It was their tendency to involve themselves in the lives of others that enabled plants to borrow a root system for fifty million years while they evolved their own.
In the 1940s, Howard argued that the widespread application of chemical fertilisers would disrupt mycorrhizal associations, the means by which ‘the marriage of a fertile soil and the tree it nourishes … is arranged’.
Agriculture causes widespread environmental destruction and is responsible for a quarter of global greenhouse gas emissions.
What? How can this be possibly true?
Worldwide, thirty football fields’ worth of topsoil are lost to erosion every minute. Yet a third of food is wasted, and demand for crops will double by 2050. It is difficult to overstate the urgency of the crisis.
Intensive farming practices – through a combination of ploughing and application of chemical fertilisers or fungicides – reduce the abundance of mycorrhizal fungi and alter the structure of their communities.
Mycorrhizal mycelium is a sticky living seam that holds soil together; remove the fungi, and the ground washes away. Mycorrhizal fungi increase the volume of water that the soil can absorb, reducing the quantity of nutrients leached out of the soil by rainfall by as much as 50 per cent. Of the carbon that is found in soils – which, remarkably, amounts to twice the amount of carbon found in plants and the atmosphere combined – a substantial proportion is bound up in tough organic compounds produced by mycorrhizal fungi. The carbon that floods into the soil through mycorrhizal channels supports
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Mycorrhizal fungi can increase the quality of a harvest, as the experiments with basil, strawberries, tomatoes and wheat illustrate. They can also increase the ability of crops to compete with weeds and enhance their resistance to diseases by priming plants’ immune systems. They can make crops less susceptible to drought and heat, and more resistant to salinity and heavy metals. They even boost the ability of plants to fight off attacks from insect pests by stimulating the production of defensive chemicals.
However, putting this knowledge into practice is not always straightforward. For one thing, mycorrhizal associations don’t always increase crop yields. In some cases, they can even reduce them.
Most modern crop varieties have been developed with little thought for their ability to form high-functioning mycorrhizal relationships.
We’ve bred strains of wheat to grow fast when they are given lots of fertiliser, and ended up with ‘spoilt’ plants that have almost lost the ability to co-operate with fungi.
If humans have unthinkingly bred varieties of crops that form dysfunctional symbioses with fungi, surely we can turn around and breed crops that make high-functioning symbiotic partners? Field is taking this approach, and hopes to develop more co-operative plant varieties, ‘a new generation of super-crops that can form amazing associations with fungi’.
Rather than breed more co-operative plants, she is working on breeding fungi that behave more altruistically: strains that hoard less, and possibly even put the needs of plants above their own.
Mycorrhizal relationships evolved to deal with the challenges of a desolate and windswept world in the earliest days of life on land. Together, they evolved a form of agriculture, although it is not possible to say whether plants learned to farm fungi, or fungi learned to farm plants.
Their name is Monotropa uniflora, and they are plants pretending not to be.
This means that the carbon that powers the life of Monotropa – the bulk of the stuff from which they are made – must ultimately come from other plants, via a shared mycorrhizal network: if carbon didn’t flow from a green plant to Monotropa through shared fungal connections, Monotropa couldn’t survive.
A study published in 2016 found that 280 kilograms of carbon per hectare of forest could be transferred between trees via fungal connections.
‘Myco’ because they depend on a fungus for their nutrition; ‘heterotroph’ (from ‘hetero-’, meaning ‘other’, and ‘-troph’, meaning ‘feeder’) because they don’t make their own energy from the sun and have to get it from somewhere else.
fermentation baths
The intense heat made me drowsy, and I thought of the fungi decomposing the wood. How easy it is when one’s not being stewed in a heap of rotting wood to take for granted that everything decays.
Their ability to cling on – and often flourish – through periods of catastrophic change is one of their defining characteristics.
Faced with lignin, this approach is hopeless: its chemical structure is too irregular.
Today, fungal decomposition – much of it of woody plant matter – is one of the largest sources of carbon emissions, emitting about eighty-five gigatonnes of carbon to the atmosphere every year. In 2018, the combustion of fossil fuels by humans emitted around ten gigatonnes.
Human industrialisation 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.)
By cultivating Pleurotus on agricultural waste – by enzymatically combusting the material – less biomass is thermally combusted, and air quality is improved.
Fungi have persisted through Earth’s five major extinction events, each of which eliminated between 75 and 95 per cent of species on the planet.
Radiotrophic fungi – those able to harvest the energy emitted by radioactive particles – flourish in the ruins of Chernobyl and are just the latest players in a longer story of fungi and human nuclear enterprise.
After Hiroshima was destroyed by an atomic bomb, it is reported that the first living thing to emerge from the devastation was a matsutake mushroom.
McCoy explained how he had trained Pleurotus mycelium to digest one of the most commonly littered items in the world: cigarette butts, over 750,000 tonnes of which are thrown away every year. Unused cigarette butts will break down, given time, but used cigarette butts are saturated with toxic residues that impede the process. McCoy had weaned Pleurotus onto a diet of used butts by gradually phasing out the alternatives.
Many fungal enzymes, like lignin peroxidases, are not specific. This means that a single enzyme can serve as a multitool, allowing the fungus to metabolise different compounds with similar structures. As it happens, many toxic pollutants – including those in cigarette butts – resemble the byproducts of lignin breakdown.
Psilocybin Mushrooms of the World
On his website is a letter from a Syrian cultivator who, inspired by Stamets, developed ways to farm oyster mushrooms on agricultural debris.
One of the ways fungi might help save the world is by helping to restore contaminated ecosystems.
In ‘mycoremediation’, as the field is known, fungi become collaborators in environmental clean-up operations.
Fungi have a remarkable appetite for a range of pollutants besides toxic cigarette butts and the herbicide glyphosate.
They are able to degrade pesticides (such as chlorophenols), synthetic dyes, the explosives TNT and RDX, crude oil, some plastics and a range of human and veterinary drugs not removed by wastewater treatment plants, from antibiotics to synthetic hormones.
For hundreds of millions of years before the plant boom in the Carboniferous, fungi made a living finding ways to decompose the debris that other organisms left behind.
a company in Finland uses this approach to reclaim gold from electronic waste.
The challenges faced by mycoremediators are analogous to those faced by brewers – without suitable conditions, yeast will struggle to remediate the sugar in a barrel of grape juice into alcohol – except that the wine barrel is a contaminated ecosystem, and we’re inside it.
Ecosystems are complex, and there is no single fungal solution that will work in all sites and conditions.
Moreover, there is a conventional remediation industry in full swing, which scrapes up polluted soil by the tonne, transports it elsewhere and burns it. Despite the expense and ecological disruption this causes, it is an industry in no hurry to be replaced.
Could the radical chemistry of white rot fungi – an evolutionary response to the very same wood boom – now help to pull us through?
The industrial production of the antibiotic penicillin was only possible because of the discovery of a high-yielding strain of Penicillium fungus.
The most revolutionary innovation emerged in 2009. The founder of the magic mushroom-growing forum mycotopia.net, known only by the handle hippie3, devised a method to grow fungi without fear of contamination. This changed everything.
I pictured crowds of enthusiasts gathering to race their homegrown fungal strains through fiendish cocktails of toxic waste, competing for a million-dollar annual award.
