How fungi made our planet green
A priest is preparing for Mass one day when a sub-atomic particle walks into the church.
The priest asks, “Who are you?”
The particle answers, “I am a Higgs boson particle.” The priest replies, “I am sorry, we don’t allow your kind to participate in Mass.”
The particle protests, “Hey, without me there is no mass.” *
Now, most of us are not going to find that joke funny. But believe me, there is a very tiny segment of the scientific community that would find it downright “rolling on the floor” hilarious.
These people are called theoretical physicists, and they study things like black holes, gravity and quantum physics. They speak in a strange language of words like muons, gluons, up quarks, down quarks, and Higgs boson particles.
Science, sports, law, military, engineering, medicine, nearly every endeavor in which humans focus on a single discipline, has its own lexicon.
I stumbled across a fascinating documentary recently that I want to share with you. And being a science documentary, it had a lot of sciencey (a newly minted word) jargon.
I frequently paused the film to look up the definition of words and terms, things like hyphae, arbuscule, Paleoproterozoic, and Precambrian. These terms are generally only used by scientists in fields of study like biology and geology.
Unfamiliar jargon explains the usual deadpan response to the joke about the Higgs boson particle in the introduction – few know the terminology of theoretical physics. Likewise, unless we are medical doctors or nurses, we may not know the meaning of terms like, dysphagia, dysuria, and nocturnal enuresis.
So, I will try to simplify this story by using as few fifty-cent words as possible, and stick to terms like “500 million years ago” rather than the esoteric “Paleozoic Era.”
This is the story about how one organism, fungi, made it possible for all of the trees, plants, soil, animals, and, yes, even us humans, to live and thrive on land.
Life, as single-celled microbes, started to evolve in the Earth’s oceans 3.5 billion years ago. Photosynthesis developed more than 2.5 billion years ago, but there was not enough oxygen – less than 2% – to allow more complex life to evolve for many more millions of years. Our atmosphere now contains 21% oxygen.
About a billion years ago, multi-celled life evolved in the oceans, paving the way for countless new and sometimes bizarre forms of sea life. The oceans would soon be teeming with life, while conditions on land were frigid and inhospitable due to a prolonged ice age.
As the planet warmed and the ice melted, it exposed a barren landscape, devoid of apparent life forms. Despite these austere conditions, the Earth was already inhabited by microbes, including bacteria and fungi. It was the fungi that would turn the rock to soil, and in doing so, open up the terrestrial world to all of the various forms of life that would follow.
To call fungi “miners” is not an exaggeration; they can drill into solid rock and have it for dinner. The airborne spores of fungi land on rock, excreting an enzyme that dissolves the stone’s surface. The minerals in the rock are now available to the fungi as a source of nutrition.
Additionally, fungi send out long and branching structures called hyphae that work their way into the rock, much like drills used in mining operations.
The soil resulting from the decomposition of rock set the groundwork for plants to leave the water and populate the Earth with all of the myriad forms of plants and trees that we see today.
Approximately 500 million years later, algae, then well established in the oceans, slowly left the seas’ briny waters for freshwater lakes and ponds. But algae were stilled confined to water at this point. Future terrestrial plants would need assistance in making their way onto land and evolving roots, leaves and seeds.
Fungi, already firmly established on land for hundreds of millions of years, found the algae a willing partner in a symbiotic dance that would lead to plants growing on terra firma. This relationship was a crucial step in the evolution of terrestrial plants, sometimes referred to as the “Big Bang” of biology.
The same fungi that had successfully mined rocks for eons now entered into a mutually beneficial partnership with algae. Fungi would provide essential minerals to the algae in return for sugars in the form of carbon.
This relationship would still exist at the water’s edge, but now, both life forms benefitted from a more economical way of obtaining nutrition. This evolutionary change would set the stage for plants to move out of the water and onto land.
About 450 million years ago, a new event came into the picture. What was to be the oldest true plant on Earth was about to meet fungi. Together, they would pave the way for all terrestrial life forms to follow.
Meet the liverwort! Doesn’t sound like something to get excited about, right? But please read on.
The first time I came upon a specimen of liverwort, and not being a botanist, I made the common mistake of assuming it was a moss. Although often found in the company of mosses, liverwort is not in the same family.
Liverworts are described as a non-vascular plant. Meaning that, unlike trees and most other plants, they do not have circulatory systems for the distribution of water and nutrition.
We always find liverworts in damp locations. My favorite group alongside the Greenbrier River Trail is bathed in morning sunlight. By afternoon, they are partially shaded by a rock outcropping where a permanent seep keeps them moist. They share this little alcove with mosses and lichen and look healthy year-round.
Liverworts do not produce flowers, fruit or woody tissue. Nor do they have seeds, relying instead on spores, much like fungi. But they do photosynthesize, so they are attractive to fungi as a source of sugars.
They do not have stomata like vascular plants. Stomata are pores that allow for the exchange of gasses, primarily oxygen and carbon dioxide. The ability of vascular plants to open and close the stomata also conserves water in the plant, an ability lacking in liverworts.
This fact alone makes liverwort particularly vulnerable to desiccation. This limitation, coupled with the fact that liverworts photosynthesize, makes the liverwort a perfect candidate for a relationship with fungi.
Fungi first entered the liverworts via hyphae, finding its way between the plant’s cells. Eventually, the hyphae found a way into the cell, creating an arbuscule. The arbuscule is a branching tree-like organ that creates sites inside the cells to exchange water, carbon, phosphorus, and other nutrients.
And so the relationship that changed the entire world made its debut. Liverwort and its fungi accomplice would change the land from a barren landscape to one with an endless variety of trees and plants, effectively turning the Earth green.
Following an extinction event 65 million years ago, fungi would once again come to the rescue.
The most popular theory for this massive extinction is that a six-mile wide asteroid or comet plummeted into the Gulf of Mexico. Dust forced into the atmosphere caused an Impact Winter that resulted in the loss of 70% of the planet’s species, including the dinosaurs.
Fungi, one of the survivor species, helped to rebuild the Earth in favor of the mammals, from which we descended.
Fungi continue to be an extremely successful organism. There are an estimated five million species of fungi, yet we have only identified a mere 1%. They play a major role in maintaining the health of our forests through a subterranean system of mycelium that connects to nearly every tree and plant.
This underground system of communication and transporter of nutrients is sometimes called the “Wood Wide Web.”
The vibrant and dense greenery that makes up our forests here in Pocahontas County owes its continued existence to fungi. So, the next time that you see a mushroom, kneel down, pat it on the head, and thank it. **
Groups interested in hiking out to see the plant that was key to the largest biological revolution of all time, the humble liverwort, may contact me for details.
From the forests of Pocahontas County,
*The Higgs boson particle was finally isolated in 2012 at the Large Hadron Collider near Geneva, Switzerland. The Higgs boson particle is believed to confer mass to other particles.
** The mushroom we see on the surface is the fruit of the subterranean organism called fungi.