It’s a bright, breezy Saturday, first week of June—a fine time to be a backyard composter here in southern New England. I wander outside to check up on my pile, first scaring off the resident robin couple that tromps across the top in search of worms and other snackables, then disrupting a squadron of hover flies that wafts above the heap in the warming, sun-shafted air.

Like a monadnock of the desert or jungle, my pile is its own stratified ecosystem. Its ragged summit and steep, flanking slopes are rife with life. I step behind the chest-high log that stands at the rear corner to pee away some morning coffee, skirting a colony of mushrooms that has sprouted at its base. Midway up the heap, a solitary soldier ant marches across the jumbled scree; a loose leaf jostles, and a foraging red worm wriggles into view. A lanky green spider has woven an elaborate web, pinning its strands to the top of the wire back fence and corner log. I catch a midge-like fly in front of my face with a clap of hands and flick the gnat from my palm onto the silvery matrix. The web quivers, and just like that the gnat is in the spider’s embrace, being spun into a bundle of silken thread.

High on the craggy mound, amid damp hummocks of sycamore seed fluff sprouting green like chia pets, more mushrooms rise from the leaf litter. These ephemeral growths are, in fact, flowers. Mushrooms sprout to release packets of fungi genes that seek to alight on a new source of food to conquer and consume. These numbers are staggering. Each mushroom issues forth millions of spores. So many are airborne at any given moment that I likely take in 10 spores with each breath, or so I read. I imagine it’s many times that amount when I’m face to face with my pile.

Every time I stick a pitchfork or shovel into the heap, I’m entering another world, one that is dominated by fungi. Like plants and animals, fungi—along with molds and yeasts—constitute a Kingdom of their own. Together, they are the most common organism on earth.

“Without fungi, all ecosystems would fail,” writes mushroom impresario Paul Stamets in Mycelium Running. The terrestrial world would be overwhelmed by dead plants and animals, as fungi, along with the even more unfathomable bacteria, are largely responsible for breaking down organic matter and releasing carbon, oxygen, nitrogen, and phosphorus into the soil and atmosphere, Brittanica informs me. In fact, various species of these decomposers have already started their work in the lower branches of trees before the leaves even hit the ground.

Hidden within my pile is a vast spread of fungi, each type working their own specialized lanes to create an overlapping network of connective tissue known as mycelium. Stamets calls it the “wood wide web” and says that under a patch of forest floor the breadth of my pile, there are more root endings in the mycelium than neural synapses firing in my brain. He’ll also tell you that as much as 90 percent of land plants are in a mutually beneficial relationship with mycelial networks, which help them absorb water and nutrients as well as build immunity from disease. Not only that, but climate researchers say the vast network of fungi beneath our feet stores over 13 gigatons of carbon, equivalent to more than one third of yearly global fossil fuel emissions.

My compost heap is a node in this worldwide network. “Every compost pile is a complex ecosystem of decomposition experts,” writes Julia Rymut, creator of compostheaven.com. “The main groups of microorganisms in soil are bacteria, fungi, protozoa and actinomycetes. These tiny little creatures are major players in decomposition. In a teaspoon of compost, you may find up to 1 billion bacteria, 440-900 feet of fungal hyphae, and 10,000 to 50,000 protozoa.”

I don’t know how many teaspoons of compost are in my pile, but I imagine enough to add many, many zeroes to Julia’s numbers. Bacteria are not only the most abundant microorganism in soil, accounting for up to 90 percent of all microorganisms in compost, they also produce enzymes that further break down the complex carbohydrates—the cellulose and lignin of woody plant matter—that are slowest to rot.

Keith Reid, author of Improving Your Soil, explains what happens next with this complex cast of characters: “Through their sheer numbers, these organisms are able to access most of the easily digested materials in the soil and incorporate them into their bodies, with the sole purpose of making more bacteria. In the process, they release nitrogen, phosphorus, sulfur and other nutrients that have been bound up in the organic matter.”

“Bacterial and fungal growth attracts a whole population of tiny animals that feed on them in much the same way that cattle or sheep graze a pasture,” Reid adds. “These include protozoa, such as the amoeba and paramecium. Large numbers of mites and nematodes also fill this role. Not all of the nutrients consumed by the grazers are used for their own growth, and the waste they release hastens the cycling of nutrients into a form that plants can use.”

Soil is likely home to nearly two-thirds of all life—everything from microbes to mammals—making it the singular most biodiverse habitat on Earth, I read in The Guardian. This includes fully 90 percent of fungi, 86 percent of plants, and 40 percent of bacteria. “The actual figure could be even higher as soils are so understudied,” the study’s authors claim.

“Scientists estimate that only 10 percent of small soil animals have so far been identified. We know even less about their relationships,” George Monbiot says in his 2022 book Regenesis, about how to transform the food system, in part by restoring the soil. “Beneath our feet is an ecosystem so astonishing that it tests the limits of our imagination. It’s as diverse as a rainforest or a coral reef. We depend on it for 99 percent of our food, yet we scarcely know it. Leonardo da Vinci remarked that we know more about the movement of the celestial bodies than about the soil on our own planet.”

Monbiot is discussing soil ecology, but the point holds true for my pile, perhaps even more so. He explains: “The soil might be the most complex of all living systems. Yet we treat it like dirt.” He likens soil to a wasps’ nest or a beaver dam: a system built by living creatures to secure their survival. “Microbes create aggregates by sticking tiny particles together with the carbon-based polymers, or cements, they excrete. In doing so, they stabilize the soil and assemble habitats for themselves. Over time, this process builds an ever more complex architecture: pores and passages through which water, oxygen and nutrients pass.”

And here I thought I was the master of the domain that is my pile. Not true. I am only the minder. As composter and organic farmer Ken Singh puts it, “The microbes in our compost are the best employees I’ve ever had. They work tirelessly. They don’t complain. They never go on strike. By golly, I love ’em! All the networks of fungi and microbes in soil are interconnected. We’re part of that, too. One day we’ll end up back in the soil ourselves.”

My humble compost heap is a hot mess, a riot of tiny creatures, all living, loving, laboring, and dying.

Scott Russell Smith is the author of “On Compost: A Year in the Life of a Suburban Garden” (Christmas Lake Press, 2024), from which this excerpt was adapted.

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