Dishing the dirt.
From the food we eat to the clothes we wear and the air we breathe, humanity depends upon the dirt beneath our feet, but for the better part of society, dirt barely gets a sideways glance. Even among the environmentally minded, soil hardly makes a blip on the radar of important causes. Despite humankind’s long relationship with soil, the stuff remains a mystery. Even our language manages to maligns it. Somehow, “dirt” has acquired a bad reputation. And it’s been codified in some of our most common idioms, with people described as “dirty rotten scoundrels,” “poor as dirt” or “dirtbags.” The modern word “dirt” itself descends from the less than complimentary Old English word “drit,” meaning “excrement.” Instead of marvelling at the mystery of soil, we mock it.
Granddads time
Since Neolithic times, when our ancestors adopted settled agriculture, our relationship with soil has been intimate and intense. Throughout history, a story has repeated itself: Great civilizations have grown where soils were fertile enough to support high-density human communities, and fallen when soils could no longer sustain our rough treatment. Mesopotamia was one and Ancient Greece suffered a similar fate. The philosopher Plato, writing around 360 B.C., attributed the demise of Greek power to land degradation: “[In earlier days] Attica yielded far more abundant produce. In comparison of what then was, there are remaining only the bones of the wasted body; all the richer and softer parts of the soil having fallen away, and the mere skeleton of the land being left.” Easter Island in the Pacific died because of deforestation, erosion and soil depletion. The 1930s Dust Bowl is perhaps the most extreme example of this consequence in modern U.S. history. For nearly a decade between 1931 and 1939, prolonged drought acted on severely misused land to cause massive erosion over millions of acres in southern Great Plains states. Destruction of a significant portion of agricultural acreage caused a mass exodus of millions of people and bogged down an already depressed national economy. According to the United Nations Convention to Combat Desertification, during the Dust Bowl years, “At least five inches of topsoil were lost from nearly 10 million acres.”
Its our turn now
Today, we are facing many of the same issues as these former civilizations: forest loss, over-consumption, dwindling freshwater supplies, overpopulation and over-worked soils nearing the brink of collapse. In many regions, including the U.S., Australia, China and Mexico, wind and water erosion are major threats. In the arid southwest of the U.S. massive irrigation is causing soils to become salty, in some cases to the point that plants can no longer grow. Soil compaction wherever farms or livestock operations (especially confined livestock operations) exist; and in many countries with naturally acidic soils, such as Ghana, the soil has become so unnaturally acidic that it can no longer grow its native sorghum crop. Declining soil fertility—the result of over-intensive farming—is a serious problem worldwide. Population pressures is forcing more and more farmers to remain on the same nutrient-depleted land, to grow their crops year after year—a practice known as “mining,” because nutrients are literally extracted from soil with nothing given in return. a third of Sub-Saharan Africa’s population is chronically undernourished, according to a study released this year by the International Centre for Soil Fertility and Agricultural Development (IFDC). The study tracked soil health across Africa from 1980 to 2004, describes the situation now facing Africa as a “soil health crisis.” Some 75 percent of Africa’s farmland is severely degraded and rapidly losing basic soil nutrients needed to grow crops, the report states, “now our poor husbandry of this essential resource is catching up with us”
Keeping your feet dry
The subject of soil is rarely billed as glamorous or sexy, but it should be. From its remarkable properties to its critical ecological importance, the dirt under our feet is a scientific wonder. Thanks to the Earth’s soils, most of the rainfall hitting our planet is trapped and absorbed, watering plants and replenishing aquifers, rivers, lakes and streams. If soil didn’t catch and apportion this water, it would run off the land into the oceans, and the continents would be barren wastelands.
If it weren’t for the stabilizing effect of soil, ancestral plants could never have survived the fierce raw weather of primordial Earth. Over millions of years, these plants and their offspring created the life-sustaining atmosphere required for land animals to evolve. Essentially an organ of Mother Earth, soil is a vital living system, the very skin of our planet that nourishes the plants we eat, the animals we use for food and fiber, and the thriving underground kingdom of bacteria, fungi, protozoa, earthworms and other microbes that are critical to the planet’s food webs.
To put it another way, without soil humans would be creatures of the sea. Only about 20 percent of the Earth’s surface is covered by land. However, much of this land is too inhospitable to support our species. Only about eight percent of the planet’s soil surface is actually arable. This means, explains Wes Jackson of the Land Institute, that all six billion people living today have but a tiny fraction of soil to thank for their survival and diverse ways of life.
Magic mushrooms
Deceptively simple to the naked eye, healthy soils are dynamic ecosystems made up of a mixture of minerals, air, water, organic materials and a healthy population of micro organisms. The range and concentration of minerals present depends on the parent bedrock. Healthy soil is also extremely porous: Air accounts for about half its volume, providing channels for water to flow, pathways for roots and space for organisms to move around. Compaction, primarily the result of heavy farm machinery and livestock, squeezes air out of soil, depleting available oxygen.
When soil is healthy, however, it is a hotbed of thriving biological activity. We can’t see most of that ongoing on but a single gram of fertile soil can contain several million microbes. One heaping tablespoon of healthy soil may contain up to nine billion micro organisms, which is more than the human population on Earth, an acre of healthy topsoil can contain 900 pounds of earthworms, 2,400 pounds of fungi, 1,500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of arthropods and algae, and in some cases, even small mammals. When this diverse soil community is disrupted or damaged, the consequences may be dire to the Earth.
You scratch my back and ill scratch yours
Long ago in Earth’s evolutionary history, early soil microbes forged one of the first symbiotic relationships with early land plants when some algae and bacteria developed the ability to “fix” nitrogen, a nutrient essential for plant growth. Nitrogen is plentiful in the atmosphere, but most plants can’t use it in that pure form. They can only use nitrogen that’s been incorporated into compounds like ammonia or nitrate. Once nitrogen-fixing organisms evolved billions of years ago, pioneer plants were able to creep onto the land.
Today, the symbiosis between soil organisms and plants is deeply intertwined. Many soil microbes feed on by-products from growing roots and, in turn, help plants by extracting minerals and vitamins from the soil. Like microscopic farmers ploughing and tilling their subterranean plots, these organisms enhance soil structure and help control plant-preying pests, cultivating an underground ecosystem. These “chthonic” (pronounced “thonic” and meaning “of the Earth”) creatures also provide another overlooked but critical function: They are perhaps the world’s most prolific recyclers. Without the help of soil microbes to break down decaying plant and animal matter, fertile soils would not exist. Dead animals would never decompose, and the litter of leaves dropped from trees every autumn would soon bury buildings and roads.
The big C
Soils also play an important role in the process of recycling carbon, the most vital element for living beings. Healthy soils can be an important carbon sink, binding up carbon that might otherwise enter the atmosphere, potentially contributing to global warming. According to the Environmental Literacy Council (ELC), soils contain twice the amount of carbon found in the atmosphere, and three times more carbon than is stored in all the Earth’s vegetation. Thanks to soil microbes, as plants and animals decompose, some of their carbon becomes part of the organic matter in soils instead of escaping into the atmosphere as carbon dioxide and when this material combines with the mucus, slime and digestive products of soil organisms, it forms the material known as humus—an extremely rich component of soil the colour of dark chocolate and saturated with carbon.
“Carbon is really the glue that holds everything together in fertile soil but when you introduce tillage and compaction, there’s excess air, and humus breaks down from long chains of carbon into carbon dioxide, which then adds to the green house affect. Since humus is highly concentrated organic matter, soils with a lot of humus tend to be more fertile. By the same token, damaged soils have less organic matter, hold less carbon, harbour a much more fragmented community of soil microbes, support fewer plants and animals, and are much more vulnerable to erosion and other problems. Organic matter is really what holds water in the soil when you have droughts or floods.
Between a rock and a hard place
While erosion occurs naturally because of wind, water and ice acting on any exposed rock or soil surface, the process has been tremendously exacerbated by human activities, especially agriculture, logging and construction. It is now estimated that humans are responsible for 60 to 80 percent of all erosion. According to the American Society of Agricultural and Biological Engineers (ASABE), lost food production is the direst consequence of erosion. A 2002 position paper adopted by ASABE, the group estimated that soil erosion is adversely affecting the ecological health of 39 percent (145 million acres) of rangeland. Worldwide,
In many places, soils are eroding faster than they can be rebuilt. Though a renewable resource in theory, soil forms very slowly. “The fastest soil regeneration is about 200 years, but it can take a million years, depending on the geologic process. Soil lost to erosion contains about three times more nutrients and 1.5 to five times more organic matter than the soil that remains behind. Further, loss of topsoil increases a soil’s overall vulnerability to erosion, thus creating a vicious, exponentially worsening cycle of damage.
Pick your Pesticide
Like fertilizers, pesticides are often over-applied. According to Blatt, pesticides have become 10 to 100 times more toxic than 30 years ago, which has resulted in about 3.5 to 5 million acute poisonings each year Farmers who work with certain kinds of pesticides have been found to get Parkinson’s disease and several types of cancer more often than the general public. Pesticides have also been linked to learning disabilities, hyperactivity, emotional disorders, weakened immune systems, birth defects and low sperm counts. Further, Blatt says that while less than one percent of pesticides applied to fields actually reach the target pests, at least 53 carcinogenic pesticides are presently applied in massive amounts to major crops. Many of the chemicals developed for agricultural use have not been tested for their effects on humans or are poorly regulated. Gradually, the world’s soils have been accumulating pesticides and fertilizers, and as these soils erode, their chemical burdens pollute the surrounding environment or enter the food supply. According to a Food and Drug Administration (FDA) study, more than 80 percent of conventional, non-organic produce tested in grocery stores had measurable levels of pesticides. .“ Our bodies are now contaminated with more than 300 man-made chemicals” (Friends of the Earth) Minowa says that most pesticides accumulate for years in people’s bodies, collecting in fat cells and other tissues. Children are particularly vulnerable to pesticides, with studies showing numerous detrimental effects to their health.
Red seas, dead zones.
When soils erode, much of the displaced sediment—as well as the pesticides and excess nutrients mixed with it—ends up washing into streams, rivers and eventually oceans. The World Resources Institute says that the surfeit of excess nutrients on the land—primarily from a massive surge in fertilizer use since the 1940s, deforestation and the burning of fossil fuels—has resulted in “a glut of nitrogen,” the effects of which “reach every environmental domain, threatening air and water quality, and disrupting the health of terrestrial and aquatic ecosystems.” The Institute adds, “Aquatic ecosystems have probably suffered the most so far. They are the ultimate receptacles of much of the nutrient overload.”
The Environmental Protection Agency (EPA) reveals that at least 40 percent of the affected stream miles and 45 percent of lake and reservoir areas were damaged because of eroded sediments. More broadly, Blatt writes that farms produce 70 percent of all stream pollution in the U.S.
Dead zones in ocean environments have expanded in size and number around the globe. Agricultural pollution originating in the Midwest is the primary cause of a chronic pollution problem in the Gulf of Mexico known as hypoxia. When excess nutrients pollute water, toxic algal blooms grow, (red seas) which suck up most of the available oxygen. This leads to the death of aquatic organisms. The mouth of the Mississippi River now has a yearly dead zone larger than the size of New Jersey and brown shrimp harvests have routinely been 25 percent of their historical catch size. The problem is similar in the Chesapeake Bay.
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