Without Fungi, How Could the Agricultural Ecosystems We Depend On Exist?
Foodthink’s Take
These life forms, distinct from plants and animals, exist as a mysterious and powerful yet often ignored presence, offering clues on the path towards human exploration and coexistence with nature. How do fungi and plants prosper together? As the link between plants and soil, what critical role do mycorrhizal fungi play in agricultural ecology? In the pursuit of maximum yield, how has this foundation of the agricultural ecosystem been destroyed?
We have selected excerpts from the new book, *Entangled Life*. By understanding the deep-seated interactions between fungi and plants in the soil, perhaps we can consider a new possibility: the future of agriculture may lie not in more chemicals, but in re-evaluating and preserving those subtle and complex symbiotic relationships within the soil ecosystem. 🍄🟫
“Human health and wellbeing inevitably depend on the efficiency with which these mycorrhizal associations operate.” So wrote Albert Howard, one of the founders of the modern organic farming movement and a passionate advocate for mycorrhizal fungi. In the 1940s, Howard proposed that the widespread use of chemical fertilisers would destroy mycorrhizal connections, and that “it is the mycorrhizal network… that binds fertile land and the trees it nourishes together.” The destruction caused by chemical fertilisers can have far-reaching effects. Severing these “living fungal threads” means damaging the health of the soil. Subsequently, the health and yield of crops suffer, and the animals and humans that consume them follow suit. “Can humans adjust their behaviour to preserve their most primary asset: the fertility of the soil?” Howard questioned. “The future of human civilisation depends on the answer to this question.”
Howard’s tone may have been somewhat hyperbolic, but in the eighty years since, the questions he raised have become increasingly acute. By some estimates, modernised agriculture has been highly efficient: crop yields doubled in the second half of the 20th century. However, a unilateral focus on yield has led to severe consequences. Agricultural development has caused widespread environmental destruction, emitting a quarter of the world’s greenhouse gases. Despite the heavy use of pesticides, 20% to 40% of crops are still plagued by pests and diseases annually. Although fertiliser use increased 700-fold in the latter half of the 20th century, the growth in global agricultural yields has begun to plateau. Every minute, topsoil the size of 30 football pitches is eroded and damaged globally. Meanwhile, humans waste a third of their food, and the demand for crops is set to double by 2050. The urgency of this crisis cannot be overstated.
Could mycorrhizal fungi provide part of the solution? This might seem a simplistic question. Mycorrhizal relationships are as ancient as plants themselves, and they have been shaping the fate of the Earth for hundreds of millions of years. Whether we realise it or not, mycorrhizal relationships have always profoundly influenced crop harvests. For millennia, traditional farming methods in many parts of the world paid close attention to soil health, thereby silently maintaining the fungal relationships of plants. But throughout the 20th century, our neglect of this caused trouble. In 1940, Howard’s greatest fear was that the development of modern agricultural technology would overlook the “life of the soil”. His fear has become reality. Agricultural practices treated the soil as a space almost devoid of life, and the underground communities that sustain edible organisms were consequently severely damaged. This mirrors much of the development of medical science in the 20th century, which conflated “germs” with “microbes”. Of course, some organisms living in the soil can cause disease, much like some microbes within our own bodies; however, the impact of most microbes is quite the opposite. When we disrupt the micro-ecology of the gut microbiome, our health suffers—many of the diseases now appearing in humans are linked to the over-eradication of “germs”. The soil is, in effect, the Earth’s gut; disrupting the complex microbial ecology within it compromises the health of plants.
In 2019, researchers at Agroscope, the Swiss agricultural research station in Zurich, published a study measuring the scale of destruction by comparing the effects of organic and traditional “intensive” farming on fungal communities in crop roots. By sequencing fungal DNA, the researchers were able to compile networks showing how fungal species are linked. They found “obvious differences” between organically and traditionally managed fields. In organically managed fields, mycorrhizal fungi were not only more numerous but the communities were also more complex: they identified 27 highly connected “keystone species”, whereas traditionally managed fields had none. Many studies have reported similar findings. Under the combined effect of tillage, chemical fertilisers, and fungicides, intensive farming has drastically reduced the number of mycorrhizal fungi and altered their community structure. Regardless of whether they are organic, more sustainable farming practices generally allow the soil to cultivate more diverse mycorrhizal communities and richer fungal mycelia.
Do these differences matter? A large part of agricultural history is a history of sacrificing ecology. Forests were felled to clear farmland, and scrubland was removed to create larger plots. Why should microbial communities in the soil be any exception? By applying fertilisers to the fields to “feed” the crops, have we not simply replaced the mycorrhizal fungi? Since we have made fungi redundant, why should we care about them?
Mycorrhizal fungi do more than just provide nutrients to plants. Some researchers at Agroscope describe them as keystone species, but others prefer the term “ecosystem engineers”. Mycorrhizal mycelia are living, sticky threads that weave through the underground, binding soil and water; without these fungi, soil and water are easily lost. Mycorrhizal fungi increase the soil’s water-absorption capacity, which can reduce the loss of soil nutrients due to rainfall by up to half. A significant portion of the organic carbon in the soil (which is a staggering double the amount found in plants and the atmosphere) is sequestered in the resilient organic compounds produced by mycorrhizal fungi. The organic carbon flowing into the soil through mycorrhizal channels supports complex food webs. Within a single teaspoon of healthy soil, alongside hundreds or thousands of metres of fungal mycelia, there are more bacteria, protists, insects, and other arthropods than there have been humans throughout all of history.
There are now many projects aimed at providing fungal solutions to agricultural problems, and Katie Field is one of the researchers receiving funding for such work. “The whole relationship is far more variable and sensitive to the environment than we tend to assume,” she told me. “Often, fungi do not help the crop absorb nutrients. The effects of mycorrhizal relationships are unpredictable, depending entirely on the species of fungus and plant, as well as the environment in which they grow.” Some studies have reported similar unpredictability. In the process of breeding most modern crop varieties, the ability to form efficient mycorrhizal relationships was overlooked. We bred wheat that could grow rapidly when fertilisers were abundant, resulting in “spoilt” plants that have almost entirely lost their capacity to cooperate with fungi. Field points out that it is “a minor miracle” that fungi still colonise the roots of such crops at all.
The nuance of mycorrhizal relationships is that the most obvious form of intervention—supplementing plants with mycorrhizal fungi and other microbes—is a double-edged sword. Sometimes, as the Hobbit Samwise Gamgee discovered in *The Lord of the Rings*, introducing soil microbial communities to plants can not only support the growth of crops and trees but also breathe life back into damaged soil. However, whether this practice actually works depends on the ecological fit. Poorly matched mycorrhizal fungi may do more harm than good to the plant; worse still, introducing opportunistic fungi into a new environment may allow them to displace native fungal species, causing unforeseen ecological consequences. The rapidly growing commercial mycorrhizal industry often ignores this fact, promoting commercial fungi as a one-size-fits-all, high-efficiency solution. Much like the booming human probiotics market, many strains are selected for sale not because they are particularly suitable, but because they are easy to produce industrially. Even with proper guidance, applying fungal inoculants to the environment is not a panacea. Like all living organisms, mycorrhizal fungi only thrive under specific conditions. Microbial communities in the soil are in a state of constant assembly; if they are continually disturbed, the connections between them will not last. For microbial intervention to be effective, agricultural practices need to undergo deeper changes—much as we must change our diet or lifestyle when attempting to restore the health of a damaged gut microbiota.
Other researchers view the problem from a different angle. If humans have inadvertently bred crops that form dysfunctional symbiotic relationships with fungi, then it must be possible to shift our approach and breed crops capable of assembling efficient symbiotic partners. Field is currently researching this method, hoping to breed crop varieties with stronger symbiotic cooperation—a “new generation of super-crops” capable of forming extraordinary connections with fungi. Keel is also interested in these possibilities, though she approaches the problem from the perspective of the fungi. Rather than breeding plants that form symbioses more easily, she is cultivating fungi that are more beneficial to the crops: strains that hoard fewer nutrients for themselves and, where possible, prioritise the needs of the plant.
In 1940, Howard stated that we lacked a “complete scientific explanation” of mycorrhizal relationships. Today, our scientific explanation remains incomplete, but as the environmental crisis intensifies, there is a growing expectation that introducing mycorrhizal fungi can transform the development of agriculture and forestry, and restore depleted ecosystems. In the early stages of terrestrial life, mycorrhizal relationships evolved continuously to meet the challenges of survival in desolate environments and harsh weather conditions. Plants and fungi co-evolved a form of agriculture—though we do not know whether it was the plants that learned to cultivate fungi, or the fungi that learned to cultivate plants. Regardless, we now face the challenge of changing our own behaviour to allow plants and fungi to better cultivate one another.
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—Excerpt from the Introduction to *Entangled Life*
Author: Merlin Sheldrake
Translator: Dinghao Luo; Reviewer: Songyan Zhou
ISBN: 978-7-5596-7775-4
Beijing United Publishing Company, First Edition, October 2024