Peak Soil

The Silent Global Crisis



A harsh winter wind blew last night, and this morning the thin snow cover has turned into a rich chocolate brown. The dirt covering the snow comes from cornfields near my home that were ploughed following the harvest, a common practice in southern Ontario and in the corn-growing regions of the US Midwest.

A handful of this dirty snow melts quickly, leaving a thin, fine-grained wet mess. It doesn’t look like much, but the mucky sludge in my hand is the prerequisite for life on the planet.

“We are overlooking soil as the foundation of all life on Earth,” says Andres Arnalds, assistant director of the Icelandic Soil Conservation Service. Arnalds is an eloquent spokesperson for the unheralded emergency of soil erosion, a problem that is reducing global food production and water availability, and is responsible for an estimated 30 percent of the greenhouse gases emissions. “Land degradation and desertification may be regarded as the silent crisis of the world, a genuine threat to the future of humankind.”

Arnalds is dead serious when he calls soil erosion a crisis. Each year, some 38,000 square miles of land become severely degraded or turn into desert. About five billion acres of arable land have been stripped of their precious layer of topsoil and been abandoned since the first wheat and barley fields were planted 10,000 years ago. In the past 40 years alone, 30 percent of the planet’s arable land has become unproductive due to erosion, mainly in Asia and Africa. At current erosion rates, soils are being depleted faster than they are replenished, and nearly all of the remaining 11 billion acres of cropland and grazing land suffer from some degree of erosion.

Most of this erosion is simply due to plowing, removal of crop residues after harvest, and overgrazing, which leaves soil naked and vulnerable to wind and rain. It is akin to tire wear on your car — a gradual, unobserved process that has potentially catastrophic consequences if ignored for too long.

Arnalds has seen our perilous future crisis by looking into the past. Eleven hundred years ago, the first Icelandic settlers came to a cold island mostly covered by forests and lush meadows, and blessed with deep volcanic soils. In a pattern repeated around the world, settlers cleared the forests and put too many animals on the meadows, until 96 percent of the forest was gone and half the grasslands destroyed. By the 1800s, Iceland had become Europe’s largest desert; the people starved, and the once prosperous country became one of the world’s poorest. “Once soil is gone, you can’t get it back,” Arnalds says. “It’s a non-renewable resource.”

Nickel and Dimed to Death

No one knows how much food-producing land will be left by 2050, when another three billion people are expected to join the current global population of 6.5 billion. What we do know is that right now, 99 percent of human food calories come from the land. Global food production has kept pace with population growth thus far thanks chiefly to the extensive use of chemical fertilizers. But food production per acre of land is starting to decline, primarily due to loss of productive land and water shortages. The latter is often the result of soil erosion because soil and vegetation act as a sponge that holds and gradually releases water. And that soil erosion, in turn, is exacerbated by chemical farming practices that over time break down soil structure.

Add to these challenges climate change’s impact on soil erosion and the competition between growing food and producing biofuels, and it’s frightening to consider the challenge of feeding nine billion people when nearly one billion go hungry right now. Arnalds summarizes the challenge: More food will have to be produced within the next 50 years than during the last 10,000 years combined. “Securing food in many places will become a crisis of rapidly growing proportions.”

Erosion largely goes unnoticed by farmers as it “nickels and dimes you to death,” says David Pimentel, an ecologist at Cornell University who has conducted extensive research on the subject. Even if there were no humans on the planet, soils would still erode. The soil formation from the weathering of rock and the breakdown of plants, however, would be faster than the erosion rate; it takes roughly 500 years to create one inch of soil. Once humans remove natural vegetation, soil is exposed to raindrops that easily dislodge it, washing soil particles into creeks, streams, rivers, and eventually into the ocean. One rainstorm will wash away .04 inches of soil. This may not seem like much, but over one acre of land that fraction of an inch adds up to tons of topsoil.

Wind also disrupts soil, and can transport dust huge distances. Dry and windy conditions blew nearly two inches of topsoil off Kansas farmlands during the winter of 1995–96. Contrary to common belief, the topsoil loss in Kansas didn’t end up being neatly deposited on farms in neighboring states. More than 60 percent ended up clogging ditches, streams, rivers, and lakes. That makes waterways more prone to flooding (further exacerbating erosion) and contaminates them with fertilizer and pesticide residues, Pimentel says.

Every rainy day or windy night steals a thin layer of soil from any exposed piece of ground until there is little left but sand and rock. “Iowa has some of the best and deepest soils in the world,” Pimentel says, “and they’ve lost nearly 50 percent in the last hundred years.”

Erosion’s potential threat to humanity remains largely ignored by the world community. When soil experts from around the world met in Selfoss, Iceland in August 2007, they concluded that an international treaty is needed to spur countries into taking action to protect their soils. The soil scientists proposed that, at the very least, soil ought to have its own year — “The International Year of Land Care” — to focus the world’s attention on soil stewardship.

But hold on a second. While politicians, CEOs, and autoworkers might not think much about soil, surely farmers, whose very existence depends on soil, don’t need a bunch of international lawyers and bureaucrats at the United Nations to tell them to protect their lands. After all, controlling erosion isn’t rocket science. By now it’s well known that agricultural practices such as protecting soil with cover crops when the land is not growing edible crops, keeping post-harvest plant residues on the land, and reducing overgrazing and forest clearance are some of the ways to protect soils.

“Farmers know their success depends on the soil, but they often have more immediate needs, such as feeding their families, paying school fees, or fleeing corrupt governments,” says Michael Stocking of the University of East Anglia in Britain, and one of the leading experts on agriculture in tropical countries. Most farmers face so many short-term challenges that it is difficult to invest in the long-term protection of the soil. Social and economic pressures force many farmers to “mine the soil” until the land is completely denuded and is turned into “badlands,” Stocking says.

Such badlands can be found in every country in the world, and are easy to spot. A more worrisome trend is the hidden danger of losing soil fertility on lands that appear healthy. “Fertility loss on good soils has a much bigger impact than further degradation of badlands,” Stocking says.

Healthy topsoil is a complex mixture of minerals, bacteria, fungi, microscopic invertebrates, and larger invertebrates such as ants and earthworms that break down nutrients and transfer them to the roots of plants. Degradation of soils diminishes this incredible below-ground biodiversity, reducing crop yield as well as soils’ ability to store and filter water and to regulate the global cycles of carbon, nitrogen, and phosphorus.

TractorErosion.epsEdwin RemsbergIn the past 40 years alone, 30 percent of the planet’s arable land has become unproductive due to erosion.

While some American farmers control erosion using low- or no-till techniques for planting, the majority are mining the soil, according to Craig Cox, executive director of the Soil and Water Conservation Society, headquartered in Iowa. “Soil conservation has taken a back seat to maximizing production,” Cox says.

As Cox drives the rural roads of Iowa, he sees fresh signs of erosion on the world’s best farmland. “It’s amazing to see the extent of erosion here, mainly because of the absence of basic soil conservation techniques,” he says. Those techniques — such as planting grasses along the edges of waterways and leaving crop residues on the soil — are some of the hard lessons learned during the dust bowl years of the 1930s. But those lessons have been forgotten — or ignored. Driven by the high costs of fertilizer and fuel, and currently lucrative crop prices, farmers are planting rows of corn right to the edge of stream banks, and sometimes in the streams themselves. “It’s amazing and discouraging to see,” Cox says.

Bad News Biofuels

It’s all the more discouraging because American farmers had reduced soil erosion by about 40 percent between 1985 and 1995, largely due to government policies like the Conservation Reserve Program (CRP). But CRP programs are now taking a back seat to the desire to cash in on the biofuel bonanza. Erosion is ignored while the US government provides billions of dollars in subsidies for biofuels. “Biofuels and climate change are real threats to America’s soil health,” Cox says.

Farmers are eagerly plowing up CRP lands, pastures, and highly erodible land to grow corn — 12 million additional acres of corn in 2007 alone — so they can profit from the ethanol boom. Ethanol is mainly made from corn, and the federal government hopes the US will be producing 35 billion gallons of the stuff by 2017. Reaching that goal would turn much of the US into a giant cornfield and has already doubled the price of corn in the past two years. Corn is particularly hard on the soil, requiring plenty of fertilizer, water, and pesticides. Cox says ethanol has sparked a “gold-rush mentality” among farmers who are mortgaging the future health of their soils for short-term profits. “There’s no question that the ethanol boom is increasing erosion.”

Not surprisingly, land prices and rents in the corn belt have jumped upward, creating additional pressure to “mine the soil to pay the mortage.” Farmland has been a popular investment for many years, and in some states, half of all farmland is rented. This reduces the incentives for soil conservation, since the farmer who works the field is not the permanent caretaker of the land. Ethanol-driven land degradation will not disappear even if the much-touted cellulosic ethanol technology is commercialized. The cellulosic process uses crop residues like corn stalks and wheat straw (rather than grains like corn or soy) to make ethanol. While cellulosic ethanol won’t directly use food as fuel, the loss of crop residues would further expose soils to erosion. And it would also reduce organic matter in soils, greatly diminishing their fertility, Cox says. “I’m very concerned there will be serious consequences for soils if cellulosic ethanol goes forward.”

Hard Rains of Climate Change

Strange new weather patterns linked to global climate change could further harm vulnerable soils. Increasing corn and soy production could expose soils to the hard rains that climate change is producing.

A number of studies have documented increased rainfall intensity in the US since 1970. In many regions, the amount of overall rainfall hasn’t changed, but the rain comes in shorter, more intense bursts, doubling the normal rates of erosion. This is particularly noticeable in the southern US, Cox says. A brand new computer climate model that uses data collected over the last decade reveals that soil scientists have substantially underestimated the amount of erosion from climate change’s hard rains. “It could be four times higher than we thought,” Cox says. And that rate appears to be accelerating as hard rains wash soil off the land, ruining streams and destroying aquatic habitat. The soil conservation techniques of yesterday may not be enough to keep soil healthy with climate change, he says. “There has been very little attention paid to the impact of climate change on soil conservation.”

“Soil is the connection to ourselves. … To be at home with the soil is truly the only way to be at home with ourselves, and therefore the only way we can be at peace with the environment and all of the earth species that are part of it. It is, literally, the common ground on which we all stand.”
— Fred Kirschenmann

There are some 2,300 billion tons of carbon locked in the world’s soils, far more than the 790 billion tons currently in the atmosphere. Land degradation, including deforestation of farmland and desertification, may account for as much as 30 percent of the world’s greenhouse gas releases, according to studies by Rattan Lal of Ohio State University. Aside from removing the natural vegetation, plowing the soil releases organic carbon into the atmosphere as carbon dioxide. Conventional agriculture methods have already reduced soil carbon by 30 and 60 percent in much of the US, says Don Reicosky, a research soil scientist with the US Department of Agriculture who is based in Morris, Minnesota. Carbon is a key ingredient for plant growth and crucial for soil fertility. For Reicosky, carbon is the primary driver of the entire living soil ecosystem: “Carbon does great things for the soil but it takes a generation to see the impacts.”

Farmers have only been able to escape the impacts of this massive loss of organic carbon thanks to cheap chemical fertilizers made from fossil fuels. But that short-term solution is just making matters worse, according to a new study out of the University of Illinois. In examining crop records and soil samples from the Illinois Morrow Plots dating back 100 years, soil scientists were surprised to see corn yields falling on plots that had received the most chemical nitrogen fertilizers and crop residues. It turns out that even with additional crop residues, fertilized soils have much less soil carbon, likely resulting in higher releases of carbon into the atmosphere.

Keeping carbon in the soil may be one of the quickest ways to reduce global carbon emissions. And if that’s not enough reason to substitute carbon storage for crop yield as the ultimate goal of farming, then the improvements in soil fertility and declines in erosion that will give us a chance at feeding a crowded world ought to.

“Blaming the farmer for these problems is futile, since we’ve created the economic system they operate in,” says Fred Kirschenmann, a North Dakota organic farmer who works at Iowa State University’s Leopold Center for Sustainable Agriculture. That system forces farmers to produce as much as possible no matter what the cost, Kirschenmann says.

A Different Way of Farming

The Kirschenmann family broke out of that system in the late 1960s when Fred learned of organic farming around the same time that his father, a veteran grower, saw their farm’s soil quality deteriorating despite best efforts to protect it. Their primary objective was to rebuild the soil, and after years of trial and error, their 3,500 acres were certified as organic in 1976; they have never looked back. Today, about 1,000 acres are in native prairie and used for grazing livestock, and the rest is managed in a diversified operation with eight to nine crops each year in three different rotations. Being debt-free — a rare privilege in farming country — enabled the Kirschenmanns to take the economic risk of finding a way to farm that was environmentally sustainable.

While organic farmers eschew chemical fertilizers, they often use intensive tilling to eliminate weeds, which can break up soils. But most organic farmers are careful to maintain cover crops and add manures to keep the soil covered and well fed with organic matter. As a result, erosion is many times less than on conventional farms. And because organic soils are more fertile, they absorb more water deeper, further reducing erosion and allowing them to better withstand droughts. A USDA study using data collected between 1994 and 2005 confirmed that organic fields have much more living soil matter than those farmed by conventional methods that did not till the soil. Corn on the organic plots also produced 18 percent higher yields.

“Agriculture’s biggest problem is the health of soil; erosion is just a symptom,” Kirschenmann says. Overcoming that problem means fundamentally re-thinking our food production systems so that the first priority is to preserve the fertility and ecological health of the land. As to how this can be done, Kirschenmann refers to the writings of Sir Albert Howard, a British botanist who wrote in 1940 that farmers ought to farm as nature does in the forest. There should always be livestock and a multitude of plant varieties; all “wastes” should be returned to the soil so that growth and decay balance each other; great pains need to be taken to store rainfall. In such a system, Howard wrote, plants and animals protect themselves from disease.

That approach may seem quaint in our technology-driven industrial culture, but Kirschenmann points out that the cows on his farm no longer need visits from the vet. Soil considerations aside, Kirschenmann wonders why — if conventional agriculture is so effective — 62 percent of Iowa farm families have off-farm jobs.

“Our system is clearly dysfunctional, and in destroying soil, we are putting enormous burdens on future generations,” he says. “We need to start to be behave as members of the land community instead of continuing to act like conquerors.”

Stephen Leahy is a freelance environmental journalist who has written for many publications, including New Scientist and The Sunday Times (London), and is the science and environment correspondent for Inter Press Service News Agency (IPS), a wire service headquartered in Rome.

You Make Our Work Possible

You Make Our Work Possible

We don’t have a paywall because, as a nonprofit publication, our mission is to inform, educate and inspire action to protect our living world. Which is why we rely on readers like you for support. If you believe in the work we do, please consider making a tax-deductible year-end donation to our Green Journalism Fund.

Get the Journal in your inbox.
Sign up for our weekly newsletter.

Subscribe Now

Get four issues of the magazine at the discounted rate of $20.