We may sit as kings on top of a richly diversified food chain, but our existence depends on fertile soil and the hidden life that dwells within it.
Nearly a week after Hurricane Irene drenched New England with rainfall in late August 2011, the Connecticut River was spewing muddy sediment into Long Island Sound and wrecking the region's farmland just before harvest.
We live on a rock.
Well, not exactly. We are 7 billion to have settled the Earth and made it a place of our own, gathering in cities and vacationing along the seaside. On the neatly stocked shelves of our supermarkets, we find foods sourced from around the world. But for all the sophistication of our modern world, there is still the wild, teeming with exotic life. In lush tropics or barren tundra, millions of species find their homes. But were it not for the thin crust of dirt that coats the surface of our mother rock, there would be none of this.
We may sit as kings on top of a richly diversified food chain, but our existence depends on fertile soil and the hidden life that dwells within it. A vast habitat that evolved inch by inch over time spans scientists qualify as geological, ultimately making life on Earth possible. As Rachel Carson wrote in 1962, “without soil, land plants could not grow, and without plants no animals could survive.”
Soil is not an inert substance, but a vast repertoire of hidden life. Billions of microorganisms are present in just a gram of dirt, while one hectare [roughly 2.5 acres] can hold up to five tons of animal life. Some, like toads, snakes, and ants, are visible to the naked eye, but the vast majority—microbes, fungi, bacteria—are invisible. The dark domain harbors a quarter of all known biodiversity on Earth, and a staggering 80 percent of its biomass. Yet for all of its abundance and proximity, the ground beneath our feet is more unknown than the depths of the ocean floor and the heights of the tropical canopy. Only 10 percent of the 2 million species of bacteria and fungi have been catalogued to date. It’s easy to understand why. There’s something lackluster about worms, fungi, and tiny crustaceans. If I were a biologist, I too would opt for Jane Goodall’s binoculars or Sylvia Earle’s deep-sea gear, over the humble microscope. Dig a little deeper into dirt, though, and you discover an intricate and fascinating universe brimming with activity. Our underground biota may largely be single-celled, but their communities administer the very building-blocks of life, delivering food, inspiring medicine, and purifying water. There may be little intelligent life afoot, but there is a collective intelligence.
Our sustenance depends on a world that is itself ravenous. The primary role of soil organisms is to decompose organic matter that falls to the ground. Worms and bacteria eat away this debris, grinding it up, decomposing it, reducing it to its most basic elements, and thus releasing the essential nutrients needed—nitrogen, potassium, phosphorus, and other minerals—for plants and crops to grow.
Understanding this process is awakening to the simple reality that nothing in this world is ever really new. Only recycled. Soil organisms are the engine of an endless reincarnation process through which land fertility is maintained.
In France, a country whose culinary tradition has been declared a world heritage by UNESCO, the divide between fine dining and famine is rooted in about a meter thick of this dirt. Thin-skinned but fertile, French lands, along with the tools of modern agriculture, have made the country Europe’s leading agricultural producer across many sectors. In 1946, France was producing a mere 16 quintals [about 3,527 pounds] of wheat per hectare. Fifty years later, yields surpassed 75 quintals.
During the past decade, however, agricultural production has been stagnating. Many agro-economists, including Marc Dufumier of the Paris Institute of Technology for Life, Food and Environmental Sciences (AgroParisTech), believe this to be a lasting structural shift under way in all countries that benefited from the Green Revolution. Or, as Lester Brown calls it, the food bubble.
If this only meant that production would stabilize at about 75 quintals per hectare, all would not be so grim. But stability is not where things seem to be headed. Several of the elements compromising food security around the world are at play here too, from soil erosion and degradation to the loss of agricultural lands for development.
Cities’ infrastructures are steadily encroaching on the most fertile farmlands. In France, it is estimated that some 6,000 km2 is lost to urbanization every seven to ten years. “The priority is always given to development,” says Lionel Vilain, an agronomist with France Nature Environnement, an environmental protection group. “Disneyland, for instance, is located on the country’s best [farm]lands.”
Once the earth has been paved over, “the loss is often irreversible,’ says Dominique Arrouays, a director at the French National Institute for Agricultural Research, who headed up a study on the state of French soils. Soil sealing, as it’s called, not only compromises food supplies for future generations, but also renders cities impermeable. Which is very bad news in a world already and increasingly subject to extreme climatic events.
The state of our soils will play an important role in whether we can mitigate and buffer the effects of this climate chaos. Fertile soil is a potentially vast carbon sink, second only to the world’s oceans. And while soils cannot entirely avert the worst flooding, their capacity to absorb water plays a role in dictating the extent to which a deluge might turn to flood.
On a given parcel of land, the fertility of soil determines whether water is more likely to infiltrate the earth’s crust, slowly percolating down to the aquifer, being purified along the way by micro-organisms specifically designed for the task, or whether it will run off the land, potentially washing away largely non-renewable topsoil into rivers and waterways. This kind of soil erosion represents a permanent loss of soil capital, a problem that affects about a third of the world’s cropland.
Villagers in Alsace’s Sundgau district, as in many other parts of this eastern French region, now look upon the spring’s thunderous skies with a measure of dread. On May 9, 2009, nearly two inches-worth of heavy rain pelted down upon 500 hectares of denuded farmland within the span of about an hour. Unable to soak up the rain, the earth instead followed the water’s course, pouring down the hill towards the village below. As the muddy blend followed the path of least resistance, streets were inundated, basements were saturated and villagers faced a heavy loss that has become a recurring menace every spring.
Over the past decade, increasingly fierce and frequent thunderstorms, of a scale seen in tropical countries, have struck the region’s erosion-prone farmlands. One hundred and fifty communes succumbed at least once to muddy flows, but despite all appearances, these were not truly acts of God. They were man-made disasters.
According to Paul van Kijk of Alsace’s Association for Agronomic Renewal (ARAA), changes in the types of crop produced in the region, along with the gradual exodus of animals on farms, which contributes to the depletion of soil organic matter, are among a host of factors “all headed in the wrong direction.” He explains: “In this area, there’s a tendency towards an increased use of summer crops such as corn. So many of the fields are now without cover when the storms come in the spring.’ Bare lands mean there’s nothing to hold the fertile soil down. “Crop choices are dictated by the market and aid systems. Awareness of problems comes with a delay.”
Charles Darwin spent his last days scrutinizing the humble earthworm, observing its single-minded busy work that keeps soil freshly tilled. He regarded earthworms as Nature’s gardeners. Soil biologists today assign them to a community they fondly refer to as “soil engineers” for their role in creating galleries that allow water to infiltrate, oxygen to circulate and roots to penetrate in the confined darkness of the underworld. While worms’ abundance may not always be a perfect indicator of healthy soil—some highly contaminated lands abound with earthworms—their declining numbers are a cause for concern.
After 50 years of deep ploughing, heavy fertilizer use, and chemical warfare on French farms, the ‘green’ revolution has taken its toll on life underground. “Farmlands are for the most part biologically dead,” Claude Bourguignon, a renowned soil biologist, told the country on the evening news on October 15, 2008. “We’ve destroyed about 90 percent of biological activity on our lands. Take a species like the earthworm. In 50 years we’ve gone from 2 tons per hectare to 50 kilos. The destruction is profound.”
According to Vilain, about 40 tons per hectare of organic matter have been lost in the great cereal plains of France: “In 30 years, organic matter content has gone from about 3-4 percent to about 1-1.5 percent. Below 1 percent is when we start having real problems with infertility. We are not there yet. But that’s where we’re slowly headed.”
“The more we have monocultures, the more we deplete microbial presence. Vineyards present the lowest microbial biomass,” says Lionel Ranjard, Director of Research at the French National Institute for Agronomic Research (INRA), who participated in the sampling of some 2,200 soils in France. “At what point do we lose so much biodiversity that the soil shuts down from a functional point of view? This is an important question.”
With average yields still reaching an impressive 70 quintals per hectare, it’s difficult for farmers to really see there’s a problem. Heavy fertilizer use over the past half-century has masked fertility problems. But the world must prepare, in agriculture as in other industries, for a dearth in the natural resources that have sustained a half-century of growth in wealth and waistlines. “Phosphorus is scarce on large parts of French territory, and we know world reserves will run out over the course of the century,” says Arrouays, of the mineral fertilizer mined in just three countries—Morocco, China, and the United States. Production of synthetic fertilizers is also dependent on oil reserves that are also peaking. “The day will come when we’ll have to limit fertilizer use,” says Bispo. “We’ll have to depend on the biology of the soil to take over. We’ll have to supply the organic matter.”
In other words, we’ll have to feed the life that feeds us.
Carolyn Lebel is a Paris-based freelance journalist specializing in investigative reporting on environmental and social issues. Excerpted from Resurgence & Ecologist (September/October 2012), a UK-based bimonthly environmental magazine.