Before plants, land was scorched and desolate. Conditions were extreme. The ancestors of land plants were fresh water algae with no roots, and with no experience foraging for nutrients and water from the ground.
To survive in this new and inhospitable environment, they had to strike up relationships with another type of organism entirely. Fungi. Fungi are largely invisible ecosystem engineers which live as networks of tubular cells called mycelium.
Mycelial networks have no fixed shape. By remodeling themselves, they can expertly forage for nutrients and water from their surroundings. In their relationship, both partners were able to provide something the other could not. Plants turned sunlight and carbon dioxide from the atmosphere into energy-rich carbon compounds, like sugars, which fungi needed to grow and survive. By partnering with plants, fungi acquired privileged access to these sources of energy.
They got fed. In turn, fungi grew into exploratory networks that could forage for minerals and water from the ground. By partnering with fungi, plants gained greater access to these essential resources.
They, too, got fed. As plants and fungi became more dependent on one another, plants evolved coarse, fleshy organs to house their fungal partners. By the time the first roots evolved, The relationship between plants and fungi was already tens of millions of years old. Fueled by high levels of light and carbon dioxide, plants spread across the world and evolved larger and more complex forms.
As plants boomed, the amount of carbon dioxide in the atmosphere dropped by 90%, triggering a period of global cooling. These alliances evolved into what we now call mycorrhizal relationships. Today, more than 90% of all plant species depend on mycorrhizal fungi.
Globally, the total length of mycorrhizal mycelium in the top 10 cm of soil is around half the width of our galaxy. The intimate associations between plants and fungi form an ancient life support system that easily qualifies as one of the wonders of the living world. In their exchange of energy and nutrients, Plants and fungi engage in sophisticated trading strategies, striking compromises and resolving dizzyingly complex trade-offs.
The influence of these quadrillions of microscopic trading decisions spills out over whole continents. Mycorrhizal mycelium is a sticky living seam that holds soil together. Remove the fungi and the ground washes away.
The carbon that floods into the soil through fungal channels supports intricate food webs. About 25% of the planet's species live underground. We are destroying the planet's fungal networks at an alarming rate through activities like industrial agriculture and deforestation. When we do so, we jeopardize the health and resilience of the ecosystems on which we depend.
Organizations like SPUN and the Fungi Foundation are leading a massive global sampling effort to create open-access maps of the planet's mycorrhizal fungal community. These maps will support conservation projects and policies that aim to halt their destruction. Mycorrhizal fungal networks have sustained and enriched life on our planet.
It's time they received the protection they deserve.