A thing is right when it tends to preserve the integrity, beauty, and stability of the biotic community. It is wrong when it tends otherwise.
—ALDO LEOPOLD, “THE LAND ETHIC” (1949)
Weaving through southern Virginia on a rainy weekday morning, I am on my way to visit Kristin McElligott. I first met her months ago at the annual conference of the Soil Society of America, where she was dutifully standing by her poster explaining her research into loblolly pine management. I liked her immediately—she was superbright, talkative, and funny (she described the forest’s designed purpose as “to produce a crapload of loblolly pine”). The drive south from Harrisonburg takes me two hours, first down I-81 and then along winding country roads. Lots of yard signs like this: “America: Pray and repent. Return to Jesus.” Lots of American flags. And lots of yard signs blending Jesus and American flags. A soil scientist at Virginia Tech, Kristin is familiar with this deep-red part of the country. Her previous degrees and work experiences have seen her living in Arkansas, Idaho, and Alaska, and she was raised in small-town Wisconsin, the first in her family to graduate from college. Given a choice, she admits, she would spend time tromping through wilderness areas in national forests or parks, but working in tree plantations has taught her much about balancing resource use and protecting the wilderness in which she feels most at home. Picture her with long brown hair in a ponytail, legs in jeans planted in hiking boots, striding off to find her research plots, her happy dog Nyssa running alongside. While the wet winding drive hasn’t been much fun, I am immediately glad I have come. This woman is passionate about soil.
“I like to think of the whole belowground ecosystem as a distorted mirror of what you see above ground, just on a different scale.” She has a spade in her hands—called a sharpshooter down south—and we are walking through stands of loblolly pine toward a ditch she wants to show me. “Most people look at the ground and they see the surface. Soil scientists like to dig as deep as we can to figure out what’s happening, how nutrient contents are changing, how microbial communities are changing, where the fungi are, where the roots go, where the water moves. All of that happens below ground.”
This is probably the first thing to learn about soil: it can be incredibly dynamic. Unless it’s been scraped away, covered, trampled, or otherwise killed, the soil under our feet can vary in consistency from one plot to another close by, as Noah Fierer and Diana Wall found in Central Park. This matters, because it tells us that all ground is not equal in its ability to sustain life.
In fact, around the world the ground holds several thousand different types of soil, and some are far more fertile than others. Made of a mix of minerals, organic matter, air, and water, soils are often described simply as “clayey” or “sandy” or “loamy.” But because soil formation is influenced by many factors, including the “parent material” (such as rock), temperature, rainfall, organisms, and time, different types of soil are probably at least as varied as the landscapes they support, making the classifying of all those types extremely difficult. Nonetheless, the US Department of Agriculture begins its soil taxonomy system by dividing soils into twelve main types, each ending in “sol,” derived from the Latin word (solum) for soil or ground. Of these it is the Mollisols (molli meaning “soft”) that are most valuable. These are the soils of the most productive farmlands in the world—the mid-latitude grasslands of the United States east of the Rocky Mountains, the steppes of Russia, and the pampas of Argentina. And here is where the States won the soil lottery. While globally, Mollisols represent only about 7 percent of soils, in the States they make up more than 21 percent. In fact, about 35 percent of US soil is either Mollisols or Alfisols, an only slightly less fertile type. In China, by contrast, only about 12 percent of the soil is usable for farming or grazing. That the United States has long been the world’s breadbasket probably has less to do with American ingenuity than with the fact that we are living on much of the richest soil on Earth.
Kristin, Nyssa, and I have stopped where a backhoe has carved a six-by-six-foot ditch that gives researchers a glimpse of the soil’s makeup here on the pine plantation. Each different type of soil has a unique character that soil scientists describe by examining its layers, or “horizons.” And when they describe it, they often sound like this: “There are more ephemerals, so there’s a lot of rapid root turnover, and those dying roots are broken down by microbes, and that creates a really thick A horizon. But these are pretty thin, and you get into the B and the C horizon very quickly. Then you have more clay accumulation. There is a saprolite layer, that’s rock, so that’s pretty much just schist bedrock parent material that has been broken down and heavily chemically weathered…”
Kristin pauses, perhaps noticing the glazed look that has no doubt descended across my face. “I don’t know how familiar you are with soil taxonomy…” she says, then laughs.
Not very, I tell her.
“It’s easier to show you,” she says, and invites me closer to where the backhoe has sliced open the ground. If you’ve ever seen a roadcut, you’ve seen an exposed soil horizon. There’s the top layer from which the grass or plants or trees emerge, and below that what look like the layers of a cake descending before gradually giving way to the underlying bedrock. This vertical cross-section view of the ground is something most of us see only as we drive to work or school or vacation.
“Let’s start from the top,” Kristin says. In this pine plantation forest, the first layer is the O layer, as in organic. This is the stuff anyone who has tromped through the woods knows well, such as rotting leaves, last year’s plants, and pine needles. Beneath this organic layer you reach what’s known as the mineral layers (for the presence of sand, silt, and clay) beginning with the A layer and descending through E, B, and C. Beneath this lies the R layer, better known as bedrock. I think again of the stunning fact that in many parts of the world, the distance between surface and bedrock is mere inches. It is the distance, it’s not too much to say, between life and starvation.
For Kristin and other soil scientists, the most exciting layer is the A horizon, or more precisely the intersection of the O and A horizons, where the organic and mineral layers interact. “This is where all the action is,” she explains. “This is the life of the soil, where most of the microbes are. And microbial happiness yields biodiversity.” It’s in this part of the soil where we see mycelium, made of fine white roots that look somewhat like a spider’s web woven with extra-large-sized filaments. The rhizosphere (meaning “related to roots”) zone around the roots is where the plant and the microbial world intersect, and it’s the hot spot for microbial activity because of the high biological and chemical activity caused by the exudate and sugars the roots excrete. Because the microorganisms that are nourished by these excretions are found in the soil’s upper layers, microbial activity decreases with depth.
We know the A horizon by another name: topsoil—the ground on which human life depends. It is also, as Kristin says, “the most delicate, the most susceptible to degradation and erosion. The part that’s right beneath your feet has the bulk of the life and the nutrients. It’s what supports plant growth, microbial life, influences hydrology. Agriculture and development often degrade this part first.”
Knowing how vital it is, it would make sense for us to treat topsoil with the greatest of care, even reverence. “Yes, but we haven’t been convinced why it matters,” she says. “I think if you don’t see it, feel it, touch it, smell it, then there is no way to have the kind of connection with soil that is needed to understand its importance. Clearly we need to use it—it’s an essential resource—but we need to use it with sound ethics. You have to be convinced that it’s important and worth protecting.”
She pauses, choosing her words. “I prefer to do that without fearmongering. But at the same time, it’s a critical issue, and without healthy soil, societies collapse.”
It’s hard to believe that American society could possibly collapse because of a lack of soil. And it’s true that we in the States are blessed to live in a country so rich in this life-giving source. But in a small world growing smaller all the time, what happens to the soil in other parts of the world—often much more at risk than our soils—will eventually affect us and our economy, and the stability of the world around us.
For example, soil scientists fear that we are wasting and damaging our topsoil—again, the layer in which most of our food grows—at an entirely unsustainable rate. How unsustainable? On average the world has only sixty harvests remaining, reported one recent study. “On average” because although in the United Kingdom that number is one hundred harvests and in the United States the number is even higher, for other parts of the world—think Africa, India, China, and parts of South America, where the human population is largest and growing ever larger—the number of remaining harvests is lower, meaning that in fewer than sixty years the topsoil will no longer support the growing and harvesting of food.
Two incompatible facts: at the very moment when we know that by 2050 we will need significantly more food, we are paving over some of our most fertile soil. Human settlements have traditionally taken root in fertile areas, and as these increasingly urban areas grow in human numbers, we are developing this ground and thus losing the best soils for growing food. In the United States, the amount of ground being lost to development is stunning—more than a million acres a year. As one result, whereas in 1980 the nation had an average of nearly two acres of cropland for each citizen, thirty years later and with ninety million people added, that number had fallen to 1.2 acres per American. “How an Exploding U.S. Population Is Devouring the Land that Feeds and Nourishes Us,” reports the subtitle of a study on sprawl. And once this ground is paved, there’s no going back. As one expert noted, “Asphalt is the land’s last crop.”
While soil sealing and sprawl are urban-focused impacts that many of us can see at our feet, other serious threats to soil take place far from sight. These are primarily threats created by agriculture, and especially industrial agriculture as practiced by Western countries and exported to developing lands. The main culprits? Intensive tilling and the overuse of synthetic fertilizers and pesticides. The resulting degradation of soils includes compaction, acidification, and the decline of organic matter. Around the world, experts say, about 40 percent of soil used for agriculture is already considered either degraded or seriously degraded, meaning that in this 40 percent at least 70 percent of the topsoil is gone. In total, in the past 150 years, half the topsoil on the planet has been lost.
This means a lot less food for an already hungry—and ever-growing—human population. “Under a business as usual scenario,” says John Crawford, an Australian sustainable agriculturist, “degraded soil will mean that we will produce thirty percent less food over the next twenty to fifty years. This is against a background of projected demand requiring us to grow fifty percent more food, as the population grows and wealthier people in countries like China and India eat more meat, which take more land to produce.”
The potential for human suffering and environmental catastrophe is enormous. Consider the East African country of Tanzania, home to a human population of some fifty million. Tanzania is also home to an elephant population already decimated from years of poaching. In just six years, from 2009 to 2015, the country saw more than half its hundred thousand elephants killed. What happens if, as projected, Tanzania’s human population doubles to more than one hundred million in the next twenty years, while at the same time the soil’s ability to produce crops diminishes? What happens to wildlife when millions of people don’t have enough to eat? And then what happens when the wildlife is gone? Similar scenarios for disaster exist all over Africa, and on other continents as well.
Even in considerably more stable situations such as in North America and Europe, we are not immune from the consequences produced by the continuing loss of soil and depleting of soil’s quality. For example, degraded soil means soil that contains fewer nutrients and grows food that is less nutritious. That’s why, as Crawford explains, modern wheat varieties have half the micronutrients of older strains, and the same is true for fruits and vegetables, many of which have lost a significant percentage—sometimes more than half—of their nutritional value just since 1950. “If it’s not in the soil,” he says, “it’s not in our food.”
All this might not matter so much if we could just find more soil, or just make soil ourselves. But for all practical purposes soil is a nonrenewable resource. The recipe for soil is incredibly complex, requiring an intricate mix of the right chemistry, biology, and physics. And it simply takes a long time to form. The rule of thumb? Between five hundred and several thousand years for an inch of topsoil.
Which brings us back to sustainability. What we need to be talking about, one soil expert told me, is, “Can we continue agriculture the way we’ve been doing it the past fifty years for the next two hundred years? The answer is almost certainly no.”
In fact, while there are many examples of how our way of life is unsustainable, our abuse of soil may rank as the worst. The British writer George Monbiot recently described our soil crisis this way:
Imagine a wonderful world, a planet on which there was no threat of climate breakdown, no loss of freshwater, no antibiotic resistance, no obesity crisis, no terrorism, no war. Surely, then, we would be out of major danger? Sorry. Even if everything else were miraculously fixed, we’re finished if we don’t address an issue considered so marginal and irrelevant that you can go for months without seeing it in a newspaper.
The number of harvests we have left, whether it’s sixty or ninety or thirty, isn’t the point. The point is that if we do not change the way we farm and build, we will run out of soil. “Almost all other issues are superficial by comparison,” writes Monbiot. “What appear to be great crises are slight and evanescent when held up against the steady trickling away of our subsistence.”
There is some good news. We actually know a lot about how to build and farm in ways that are less destructive to soils. “No-till” farming has been shown to successfully grow crops without the destructive force of tilling; organic farming methods can start to address the overuse of chemical fertilizers that have turned much of the world’s soils from fertile ecosystems into sterile holders of plants; and the planting of cover crops can return carbon and nutrients to the soil. “The most important lesson is to keep the soil covered,” Kristin McElligott told me. “When do you ever see bare soil in nature, naturally?”
So why do we continue to farm in a way that treats soil so destructively?
The standard reason given by the agriculture industry is that in order to feed a human population of seven billion and growing, there simply is no other way to farm. But while no one questions that feeding so many people is an enormous task that will only grow more challenging, this position seems to ignore reality. Explained one agroecologist, “People worry about what will happen if the oil runs out. But they don’t seem to worry about what will happen if we run out of soil.”
After talking with dozens of “soil people” and reading dozens more, I begin to think that the destruction of the soil upon which we depend has much to do with how we see the ground beneath our feet. And that is why I find myself heading to the state that represents the heart of American agriculture.