The scoop on dirt: why we should all worship the ground we walk on.
From the food we eat to the clothes we wear to the air we breathe, humanity depends upon the dirt beneath our feet. Gardeners understand this intuitively; to them, the saying "cherish the soil" is gospel. But for the better part of society, dirt barely gets a sideways glance. To most, it's just part of the background, something so obvious it's ignored.
Even among the environmentally minded, soil sags well below the radar of important causes. But the relationship between soil quality and other aspects of environmental health is intricately entwined. What's more, it's a relationship that encore passes a vast swath of territory, from agricultural practices to global climate change, and from the well being of oceans to that of people.
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 "dirt-bags." The modern word "dirt" itself descends from the less than complimentary Old English word "drit," meaning "excrement." Instead of marveling at the mystery of soil, we have mocked it, by dredging and paving; desiccating and polluting; and working it to exhaustion.
Now our poor husbandry of this essential resource is catching up with us, in the form of disconcertingly rapid erosion and loss of farmland, widespread agricultural pollution, damage to fisheries, and alarming levels of pesticides and other chemicals building up in our bodies. 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 goldmine of scientific wonderment, and it's about time people got excited about soil.
Soil is Special Stuff
Soil types vary considerably on our planet, from the hottest deserts to the coldest poles. Soil directly and indirectly affects agricultural productivity, water quality and climate. 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.
Anatomy of Healthy Soil
So what is healthy soil? 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 microorganisms. 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 work, save perhaps on particularly rainy days when earthworms flock to the surface or a large insect scuttles across the ground. But a single gram of fertile soil can contain several million microbes. One heaping tablespoon of healthy soil may contain up to nine billion microorganisms, which is more than the human population on Earth, points out Harvey Blatt, author of the 2004 book America's Environmental Report Card. 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.
Plants are the first to suffer from damage to the soil community. Interestingly, soil microbes play a critical role in plant health. Long ago in Earth's evolutionary history, early soil microbes forged one of the first symbiotic relationships with early land planks when some algae and bacteria developed the ability to "fix" nitrogen, a nutrient essential for plant growth. Nitrogen is plentiful in the atmosphere, but 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. As these early plants gained a foothold on the rocky ledges poking out of the primordial seas, they helped build the terrestrial soils.
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 plowing 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 Carbon Link
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. Paul Hepperly of the Rodale Institute's experimental research farm in eastern Pennsylvania defines organic matter as "mostly the resistant remains of plants." 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 color of dark chocolate. Hepperly explains that humus is saturated with carbon.
"Carbon is really the glue that holds everything together in fertile soil," Hepperly says. "When you introduce tillage and compaction, there's excess air, and humus breaks from long chains of carbon into carbon dioxide, which then goes into the air." 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, harbor 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," Hepperly says. "If you take away the glue, everything falls apart."
Soils in Trouble
Unfortunately, in many parts of the world, that "glue" is deteriorating rapidly. The explosion in human population, fuelled by agricultural and technological advancements, has led to soil erosion, compaction, salinity and loss of fertility. As the figurative "lifeblood" of many organisms, including humans, problems at the level of soils may reverberate through entire ecosystems--or civilizations.
In the 1930s, Hugh Hammond Bennett--a USDA scientist widely regarded as the "father of soil conservation" (see sidebar)--commented, "Soil erosion is as old as agriculture. It began when the first heavy rain struck the first furrow turned by a crude implement of tillage in the hands of prehistoric man."
Any discussion about the health of soil ends up addressing agriculture. Since Neolithic times, when our ancestors adopted settled agriculture, our relationship with soil has been intimate and intense. Throughout history, the 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. According to the International Task Force on Land Degradation, the great early civilizations of Mesopotamia arose because of the richness of their soils, and collapsed because of declines in soil quality. Poor land management and excessive irrigation caused soils to become increasingly degraded, leading to power struggles, migrations, and ultimately, the collapse of the Fertile Crescent civilizations.
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."
Many experts also blame the collapse of the great Mayan civilization and the peaceful Harappan society of the Indus valley on soil exhaustion and erosion, resulting from agricultural practices and clear-cutting of forests. According to Jared Diamond, a UCLA professor and author of the books Guns, Germs and Steel and Collapse, 90 percent of the people inhabiting Easter Island in the Pacific died because of deforestation, erosion and soil depletion. In Iceland, farming and human activities caused about 50 percent of the soil to end up in the sea, explains Diamond. "Icelandic society survived only through a drastically lower standard of living," he says. Not surprisingly, the practice of destroying soils by torching or salting farms and fields has been employed by armies in wars, from Alexander the Great to Napoleon.
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. While other social and economic factors also threaten soils, intensive, unsustainable agricultural practices continue to bear the brunt of the blame, despite lessons from history. Non-agricultural activities such as logging, construction, off-road vehicles, floods, droughts and fires also increase erosion, but the Natural Resource Conservation Service (NRCS) reports that agriculture is responsible for at least 60 percent of the erosion afflicting the U.S.
In America, our history has arguably been shaped from the outset by unsound farming practices. From the moment the first Europeans stepped off the boat, we set plow to earth and began to dredge the soft, overworking it through constant tilling and planting. "The farming practices of our forebears caused a one percent per year breakdown of essential organic matter, so that in 50 to 100 years families could no longer farm their home plots," explains Hepperly. He adds that the need to seek new fertile soils and farmsteads was a major factor in the westward movement of settlers.
Fortunately for those early colonists, there was always an abundance of fresh, new land. Today, humans have colonized just about every viable land surface on the planet. No fabled flesh frontiers remain. As the world's human population continues to grow, placing ever more strain on already stressed soils, will human societies find themselves near the brink of collapse?
Threats to Soils
Not all soil problems are equal everywhere. 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 abounds wherever massive farms or livestock operations (especially confined livestock operations) exist; and in many countries with naturally acidic soils, such as Australia and Ghana, overuse of fertilizers is causing soils to become even more acidic. In the case of Ghana, Hepperly says that 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, but it is particularly acute in Sub-Saharan Africa, where severe depletion of soil nutrients is a major cause of poverty and hunger.
Among the soil problems, it is generally agreed that soil erosion is one of the most serious, in part because it often precedes or accompanies other forms of soil degradation or environmental problems. 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.
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."
While erosion isn't as dramatic in the U.S. today as it was in the 1930s, the problem continues to haunt farmers and urban developers. In a 2002 position paper adopted by ASABE, the group estimated that soil erosion is damaging the productivity of 29 percent (112 million acres) of U.S. cropland and is adversely affecting the ecological health of 39 percent (145 million acres) of rangeland. Worldwide, erosion is one of the biggest causes of soil degradation. "An outrageous amount of soil is being lost" says Craig Minowa, an environmental scientist with the Organic Consumers Association (OCA).
In many places, soils are eroding faster than they can be rebuilt. Though a renewable resource in theory, soil forms very slowly, measured in centuries. For all practical purposes, the soil we lose to erosion will never be replaced in our lifetimes.
"The fastest soil regeneration is about 200 years, but it can take a million years, depending on the geologic processes;' says Dan Yoder, a professor in the Department of Biological Systems Engineering and Soil Science at the University of Tennessee. "Coarse sand, for instance, doesn't form soil very easily."
Hepperly says that each American erodes an average of 3.5 tons of soil yearly. "In fact, it is our biggest national export," he quips. A single rainstorm can wash away centuries-old accumulations of soil from damaged, neglected or badly managed ground.
Human-caused erosion (also known as "accelerated erosion") is most damaging to topsoil, the soil's uppermost layer. In addition to being the most productive soil layer (it contains the highest concentration of organic material), topsoil is also the layer in which plants grow best. But topsoil is also the thinnest layer, usually not more than a foot deep. Preston Sullivan of the National Sustainable Agriculture Information Service says that 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.
The developing world is especially at risk from the negative effects of soil erosion and declining soil fertility. In Africa, many nations are facing a veritable soil health crisis, due in large part to increasing population pressures, poverty, and the limitations inherent to many tropical soils. Tropical soils are naturally lower in fertility, and also foster increased weeds and pests, says Hari Eswaran, national leader of the NRCS-affiliated Office of World Soil Resources and an expert on soil erosion problems.
"In Nigeria two to three years ago, I visited a farmer growing tapioca, a tuber which is a staple crop there. His average yield was about three tons per acre," Eswaran says. "In contrast, the average yield is 30 tons per acre in India ... You combine these problems, and that's why they practiced shifting cultivation. After two years, production decreased and people moved on. That only works with lower population.
Population pressures are now forcing 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. Among other problems, farmers often have practically no access to soil-enriching fertilizers.
"Here in the U.S. land starts to degrade and farmers see it in terms of decreased productivity. They counteract it with massive amounts of fertilizers and chemicals," Eswaran says. But in Africa, farmers often have to walk for miles to buy fertilizer, he explains. Many are also ignorant of proper fertilizer use and simple farming techniques that could significantly minimize soil damage. The result is that at least a third of Sub-Saharan Africa's population is chronically undernourished, according to a study released this year by the International Center for Soil Fertility and Agricultural Development (IFDC), a U.S.-based nonprofit. The study tracked soil health across Africa from 1980 to 2004, and 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. Many sub-Saharan countries can't feed themsleves;' says Eswaran.
A 1995 study published in Science concluded that the loss of soil and water from U.S. cropland decreases agricultural productivity by about $27 billion per year. A 2000 story in the Australian rural weekly paper Landline estimates that soil degradation costs Australian farmers $2.5 billion a year in lost production. It added that nobody has even calculated the off-farm costs of soil degradation, such as salt-polluted rivers or the loss of biodiversity and wildlife habitat.
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.
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, 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, says Hepperly, and brown shrimp harvests have routinely been 25 percent of their historical catch size. The problem is similar in the Chesapeake Bay.
Erosion isn't just an agricultural phenomenon. Urban erosion is an equally significant problem--one that has often been overlooked, but is becoming more serious as population pressures fuel development and urban expansion. Housing and construction projects gouge the soil and strip its vegetation, leaving it exposed to the elements for long periods of time. Erosion rates remain higher after construction is completed, as vegetation is reduced and rooftops shed water that would have been trapped by plants. When it rains, the soil washes away like sand from a shovel, eventually finding its way into city sewers and gutters, and eventually, streams and waterways.
"One of the hot areas of soil science is erosion at construction sites," says the University of Tennessee's Yoder. "In agriculture, I think we have a pretty good handle on how to control soil erosion. Construction sites are something else. You have steep slopes, and they're completely bare."
One of the major problems with urban erosion, Yoder explains, is that there is currently no unified national standard for erosion monitoring and control at construction sites. While soil conservation measures on farms were adopted in the 1970s and '80s requiring farmers who receive federal support to prove they had adopted conservation practices, no such regulatory structure exists at construction sites. "You have the EPA watching, but each state has its own agency for permitting of construction sites" Yoder says. "There's not much concentration on soil conservation."
The available statistics on construction site erosion are disconcerting. According to Cathy Rofshus, an administrator for the Shell Rock River Water District in Minnesota, "The Environmental Pollution Control Agency estimates that 20 to 150 tons of soil per acre runs off construction sites with rainwater. That would be 1,600 to 12,000 tons of soil for an 80-acre site." Wal-Mart alone may thus be responsible for between 1.5 million and 11.25 million tons of soil erosion in the U.S. through construction of its stores. According to AlterNet, Wal-Mart's 3,600 U.S. stores and 100 distribution centers, including their parking lots, currently occupy roughly 75,000 acres.
To minimize erosion at construction sites, Yoder says there are a number of fairly simple measures developers can employ. Silt fences can be placed at the bottom of slopes to stop sediment from getting into waterways. A wall of soil may build up behind them, which is then returned to the hillsides. Sediment basins are more permanent versions of these structures that trap runoff and allow the suspended soils to settle out before water carries sediments into streams. Erosion-control mats are usually made out of straw and placed on the tops of slopes so that wind and rain will be less likely to carry soil away. Hydro-mulching is a similar measure whereby a water-seed-straw mix that will absorb rain is blown over the bare land.
The Funding Erodes, Too
Even as soil problems have increased in severity, federal funding of soil research and conservation has steadily declined over the years (see sidebar, "The Lay of the Land"). Where as the government practically lavished money on soil projects in the 1930s and '40s, scientists proposing soil-focused research projects today are having trouble getting funded. They have to compete with research proposals on "hot" science topics that are more attractive to major grantees, or they have to adapt their research to fit the funder's interests, Yoder says.
Staff in Eswaran's World Soil Resources office once traveled extensively in developing countries educating farmers about soil management and providing support. For the past 10 years, however, Eswaran says the office "has had no funds to travel." Most of the direct scientist-to-farmer work once possible with federal funds--primarily from USAID--has had to be aborted. USAID gave Eswaran's office about $65 million in the early 1980s for agricultural research. By the early 1990s, his funding had dropped to about $10 million, a decrease of almost 85 percent.
And yet in some African countries, simple education of farmers in better land management techniques and better access to fertilizers could arrest the worst of problems. In Yoder's view, part of the problem is that "nobody thinks long-term anymore."
Is Bigger Better?
One reason why agriculture can be so detrimental to soils is because of the sheer scale of most farming operations today. According to USDA, since 1900 the number of farms has fallen by 63 percent, while the average farm size has risen by 67 percent. In 1900, the average farm size was less than 100 acres; in 2002 it was more than 400 acres. Farm operations have also become increasingly specialized, from an average of about five commodities per farm in 1900 to an average of one per farm in 2000. Most important, the USDA says that all of this has taken place with no variation in the amount of land being farmed.
Small family farms have steadily disappeared in the midst of increasing urbanization and decreasing profitability, and the mega-farms that now dominate U.S. agriculture have transformed into "agribusinesses" that receive most federal farm subsidies. What this means is that the intensity of agriculture has dramatically increased.
While individual farms have shrunk, yields have increased, thanks to growing reliance on pesticides, herbicides and fertilizers. But while this practice has allowed farmers to control pests and nutrients in the short term, the net result is artificial enrichment of overworked soils that often lose stability.
According to David Tilman, who wrote the 1998 Nature article "The Greening of the Green Revolution" only about half of all fertilizers are absorbed by plants. The remaining chemicals pollute the atmosphere, soils and waterways. OCA's Minowa attributes much of this chemical overuse to a comparative detachment of industrial farm workers from the land. "Farmers working their family land knew they'd be working that plot, and their children would be working that plot, for a long time, so they would take care of it and respect it more" he says. "Agribusinesses, on the other hand, are primarily concerned with profitability, which means using the land more intensively:'
Yoder cautions against placing all the blame on agribusiness, however. Sustainable management of farms can be expensive, he says, and small farms sometimes can't afford the risk.
Farmers generally apply some fertilizer to their crops, although some are "natural" including cover crops used in winter to help feed nutrients back into the soil. However, most fertilizers employed by conventional farmers are synthetic versions of the NPK (nitrogen, phosphorus, potassium) formula. These nutrients are depleted from intensively worked soils over time. But synthetic fertilizers can also wreak havoc on the underlying ecology, as well as on humans and ecosystems far away from the farms on which they are used. EarthWorks News reported, "The high salt content of many synthetic fertilizers ... may overwhelm the natural balance of organic decomposition taking place in the soils."
Like fertilizers, pesticides are often over-applied. According | to Blatt, pesticides have become 10 to 100 times more toxtic 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.
For instance, the manufacturers of Atrazine, one of the most commonly used pesticides, recommend that farmers apply two pounds per acre, Hepperly says. However, only half of it breaks down in a year, so at the end of the planting season, one pound still remains through the following year.
Why do farmers continue to apply so much? By recommending that farmers apply more of the pesticide than is needed, the chemical manufacturers reap a bigger profit. What is particularly troubling about Atrazine, though, is that recent studies have linked very low doses to developmental problems in frogs, which are experiencing global declines. Several European countries have now banned the chemical.
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. Minowa says that most pestiddes 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.
Hepperly believes our continued use of pesticides and fertilizers has made the soil problems we faced 20 or 30 years ago much more severe. "This can be measured in water quality;' he says. "Dead zones in ocean environments have expanded in size and number around the globe."
Factory Farming and Feed Lots
A nother side effect of modern agribusiness is that instead of raising livestock and crops together, animals are now raised on enormous Confined Animal Feeding Operations (CAFOs), while crops are mass-produced on separate farms. Concentrating so many heavy-hoofed animals in a relatively small space wreaks havoc on soil health, ruining its porous structure. Excess animal waste over-fertilizes soils, and pollutes the environment.
Once upon a time, small farms used the manure generated by their animals to naturally fertilize their crops. Today, however, it is too costly to transport the mass quantities of manure generated on CAFOs to the big crop-producing farms. As a result, these farms make heavy use of synthetic fertilizers in order to support high-intensity monocrops, while the CAFOs generate huge amounts of animal waste, which eventually pollutes the surrounding land.
Some would argue that commercialized agriculture has been necessary to feed the world's growing population, and that as a result, it has been beneficial to society. While this is true in some respects--particularly in our ability to supply starving people in developing nations with food, and in our ability to allow cities to grow even as farmland has been shrinking--agribusiness has, on the whole, fostered some disturbing social and environmental trends. In the long run, dramatic increases in crop yields may have disastrous implications.
Minowa likens the current state of modern agriculture to speeding up on the highway. "People have their foot on the pedal and don't see how much gas they're using," he says. "But intensive agriculture is disrupting the microorganism and nutrient ratios in soil, and causing a build-up of pesticides." At some point, the system may run out of gas and crash.
Fortunately, there are measures we can take today to help save our soil. Educating farmers in the U.S. and abroad about the damaging effects of intensive agriculture and over-application of synthetic fertilizers and pesticides is a good place to start.
Sustainable Farm Management
Progressive farmers can reduce damage to soils by reducing tillage, managing irrigation to minimize water loss (and hence salt build-up from evaporation) and planting cover crops. Planting wind barriers on hillsides (also known as "shelterbelts") and maintaining healthy grass cover on pastures can help prevent erosion. If streams run through a farm property, planting grassed waterways along the stream banks can help trap eroded sediment and bind it up, keeping it from entering and polluting larger water bodies.
Tillage, a standard procedure during planting season, is extremely damaging to soils over time. While it has historically helped increase plant yields, it also fosters erosion and breakdown of organic matter by killing worms, chopping up residual root and plant parts, and disrupting the microbe community. Ultimately, farmers are forced to make up for declining soil fertility by relying on synthetic fertilizers.
No-till has been touted as one alternative, but it has drawbacks of its own. Hepperly says that no-till often leads to greater rather than less pesticide use (about four times as much, he says), and ends up costing farmers more money. Because of this, the pesticide industry is one of the bigger proponents of no-till. "Is tillage the lesser evil, or reduced pesticides the lesser evil?" Hepperly asks. He argues that a combination of no-till for some crops and tillage for others will help reduce both damage to soil structure and use of synthetic chemicals.
Pesticide use can be greatly reduced by adopting an integrated pest management system, which relies on such practices as crop rotation (which deters plant-specific pests from taking up long-term residence in soil) and natural biological controls. Planting marigolds around tomato plants in gardens to discourage pests is one such example. Many other plants or insects have similar beneficial pest-deterring properties when intermixed with agricultural crops. Jerry Bisson, an environmental compliance officer with USAID, says his agency promotes developing world farmers using simple technologies to improve land management. "Farmers can be taught to use string, rock and wood as barriers, for example. They can see how they benefit."
The Organic Revolution
Even without becoming organic farmers ourselves, we can do a lot to help soils. Buying organic food is one of the first actions consumers can take to support sound conservation practices. Organic agriculture is based on the principle that healthy soil is the foundation of the food chain. In order to be certified "organic" by the U.S. Department of Agriculture (USDA), stringent requirements must be met. As a result of these standards, organic farms employ only natural fertilizers. Healthy populations of soil microbes thrive on organic farms, and effects of erosion and soil compaction are greatly minimized.
Supporting organic farming also tends to support strong local communities. Mega-farms have no obligation to circulate their profits back into local communities, and often don't. Buying locally has the double effect of encouraging investment in healthy towns and a healthy environment. Even if organic goods aren't from a local farm, buying them still sends a powerful message that sustainable soil is a national priority. That message seems to be getting through: in March 2006, statistics showing a leap in organic food sales caused Wal-Mart to announce plans to stock more than 400 organic items in its stores (see Currents, "High-Volume Organic" this issue).
While industrial agriculture currently dominates the market, it may not remain king of the hill indefinitely. As the costs of oil and natural gas go up, the price of fertilizers, a majority of which are fossil fuel based, is also increasing. According to Yoder, the price of nitrogen fertilizer has almost doubled in the last two years. Because mega-farms rely so heavily on fertilizers, and then must pay for transport to supermarkets scattered around the country or globe, these farms are seeing costs skyrocket.
Organic farming is the fastest growing sector of the farm industry, and is becoming increasingly profitable. Can organic farming achieve the same high yields as conventional agriculture? For 25 years, the Rodale Institute has been conducting a continuous experiment on its Pennsylvania farm, comparing organic and conventional methods. Throughout the study, the organic plots have repeatedly performed better than the conventional plots, especially during severe weather events.
The Big Picture
There are deeper societal issues that need to be addressed when looking at soil conservation on a global scale. First, urbanization needs to be better managed. The wholesale conversion of rural lands to concrete jungles consumes and degrades vast amounts of soil. In many places, particularly much of the developing world, the roots of mass migration to cities--poverty, war, desperation--need to be addressed. Franklin suggests, "The more small farmers have control over their land, the less likely they'll be to mine the soil." In addition, cities can mitigate damage to soils by supporting low-impact development and construction of eco-roofs and integrated parking lots.
Fundamentally, Hepperly believes people need to reestablish their connection to the land. "We need people to grow something--tomatoes, raspberries, flowers--so they understand why the land, returning soil to its rightful place in the very center of our lives. CONTACT: National Sustainable Agriculture Information Service, (800)346-9140, www.attra.org; USAID, (202)712-4320, www. usaid.org; World Resources Institute, (202)729-7600, www.wri.org.
RELATED ARTICLE: Just deserts: bad soil practices create a sea of sand.
Drylands cover 41 percent of the Earth's land surface. Of that area, desertification has rendered 20 percent unfit for human use, and an additional 70 percent remains vulnerable. According to the United Nations, desertification is degrading soil quality in 110 countries, directly impacting 250 million people and threatening a billion more, all without creating a single new desert.
"True deserts have evolved for millions of years," says Exequiel Ezcurra, research director for the San Diego Natural History Museum. "When you get degradation in Oklahoma, you don't get a desert popping up, you just get barren soil."
The UN has declared 2006 the International Year of Deserts and Desertification. The latter phenomenon occurs around deserts on semi-arid and semi-tropical land, which is often used for grazing or cropland. "Desertification is caused by human activity and exasperated by climate impact," explains David Mouat of the Desert Research Institute. Overgrazing and improper farm management leaves land vulnerable to being stripped bare, the result of erosion. Wind scatters the exposed soil during droughts, and water washes it away during rainfall.
According to Charles Hutchinson, director of Arid Land Studies at the University of Arizona in Tucson, desertification changes more than just the appearance of the landscape. "Once you've removed the cover of vegetation you're going to change what's going on in the soil. Many times it won't recover. In many parts of Africa they're getting 'shrubification,' a change from grasslands to scrubland," Hutchinson explains.
Though desertification endangers semi-arid lands in both Africa and Arizona, as well as in China and Spain, developing countries feel the consequences of denuded land more immediately. "What people do to cause desertification occurs in both developed and developing countries," says Mouat. "The difference is in how people are affected and what they can do about it."
Reversing the damage is impossible or too costly for developing nations, and the changes affect the livelihoods of local communities. "When biodiversity is impacted," Mouat cautions, "that impacts people's ability to extract goods and services from the land." Herds no longer have the grasslands as a food source, and degraded soil does not produce crops. Desertification currently costs the world $42 billion worth of agricultural production a year.
A country's desertification quickly becomes a problem for its neighbors as well. Dust clouds, drawn into the air by high-pressure systems over central China, have closed Korean airports, and Hutchinson claims that the same dust clouds make their way across the Pacific to North America. "When that surface is exposed it can be moved by wind," he says, "and we're tracking the movement of those plumes of dust over to the U.S." The dust can cause eye infections and respiratory problems, though Mouat doubts that those effects will be particularly severe in the U.S. Still, he emphasizes the importance of an international response. "It's important to recognize it's a global problem," he says, "not just because of the climate feedback, but because we're a global society."
Avigad Vonshak, director of Israel's Jacob Blaustein Institutes for Desert Research (see Currents, this issue), agrees with Mouat's conclusion, and takes it a bit further. "It's a mistake to refer to desertification as something not affecting all of us," he says. He cites dust storms as a factor in the 50 percent increase in eye infections over the past few years in U.S. and European babies. "Sand dunes in Africa are usually stabilized by a crust cover," Vonshak says. "If you have humans acting in an unsustainable way, the natural cover is destroyed and the dunes can move and produce dust storms. This is globalization." CONTACT: Desert Research Institute, (775) 673-7300, www.dri.edu; UN Conference to Combat Desertification, (011)49-228-815-2800, www.unccd.int.
--Paul Gleason and Stephanie Freid
RELATED ARTICLE: Toxic sludge: is it good for you?
Can toxic waste be turned from a disposal problem into a useful and benign fertilizer? That's the question some scientists and activists are asking about a product that is routinely used by farmers and home gardeners to feed their soils.
The U.S. Environmental Protection Agency says it "has continually encouraged the beneficial reuse and recycling of industrial wastes, including hazardous wastes, when such wastes can be used as safe and effective substitutes for virgin, raw materials."
The key words, opponents would argue, are "safe" and "effective." In the mid-1990s, fertilizers sickened small-town Washington farmers and killed their crops, the farmers say. The big problem, according to reporter Duff Wilson who broke the story in the Seattle Times, was that companies did not disclose the potentially dangerous chemicals their fertilizers contained, such as heavy metals.
There have been many reports of sludge-related illnesses. A 2002 scientific study published in Cornell University's New Solutions (co-authored by E cover girl Summer Rayne Oakes) tracked symptoms, including headaches and respiratory problems, involving 328 people in 39 incidents in 15 states. The study concluded that greater investigation of health claims is needed, and that the practice of spreading sewage sludge on the soil surface "appears to present a particularly high risk."
In 2003, a coalition of 73 groups, including the Organic Consumers Association (OCA), petitioned the Environmental Protection Agency (EPA) to place a moratorium on the land application of sewage sludge. An OCA spokesperson said the food supply was being "poisoned" by the sludge. But the petition was denied.
Patricia Martin, who was mayor of Quincy, Washington when Wilson wrote his stories, says that current rules fail to protect the public. Her group, Safe Food and Fertilizer, wants the federal government to force state regulators to cap various contaminants at set amounts.
Others say that reforms have already occurred. "Everybody understands the need to look for these contaminants because of the Duff Wilson episode," says Rufus Chaney, a U.S. Department of Agriculture (USDA) scientist. Companies meet safe metal limits that states set, he says.
The Washington farmers got what they paid for, says George Latimer, who monitored fertilizers during the scare as the Texas State Chemist. Small-time dealers might sell their contaminated sewage sludge before regulators can stop them, Latimer says, but people who buy only well-known fertilizers are safe. "I don't think, in general, that the consumer needs to be concerned about heavy metals in fertilizers," he says.
But Shiou Kuo, soil scientist and professor at Washington State University's Puyallup Research and Extension Center, sounds a cautionary note. If plants do not pick up metallic "so-called trace elements," he says, they will remain in the soil, and could run off into surface water.
States such as Texas follow Canadian standards, which have tighter metal limits. Many other states' rules are a lot less demanding: Chaney, meanwhile, says Canada's rules are excessive.
While both countries' fertilizer labels still list only beneficial ingredients, not potentially dangerous metals, some states now maintain on-line databases that itemize the ingredients of fertilizers. Martin says that current laws allow farmland to be "used as a disposal site." And to that Kuo adds, "Once you find out there is a problem, it's too late." CONTACT: Safe Food and Fertilizer, (509)787-4275, www. safefoodandfertilizer.org.--Adrian Larose
RELATED ARTICLE: John Havlin: soil scientist.
Interviewed by Jim Motavalli
If soils do indeed achieve the higher profile they so desperately need, John L. Havlin will be one of the people to thank. The professor at North Carolina State University is past president of the Soil Science Society of America, and a dedicated campaigner whose work is helping to establish the House of Representatives Soils Caucus and a $4 million Smithsonian educational exhibit on the subject, opening in 2008. The goal is to help the national museum's six million visitors a year "understand how soil is intricately linked to the health of humanity, the environment and the planet."
It's often said that the Native Americans had a special relationship with the Earth. Do you think we need to rekindle a relationship with the earth, meaning the soil beneath our feet?
There's no question that people today do not understand the importance and value of soil and other natural resources to their very existence. Yes, it needs to be rekindled. People need to understand that if we didn't have that thin layer of material on the Earth's surface we couldn't exist on this planet. And when I say it's a thin layer, let me use this example from our grade: If you take an apple, the thickness of the skin of the fruit is approximately the soil on the Earth's surface. And if you slice that apple in sections 32 times, one of those small sections is the amount of land that we produce food on.
Is part of the problem the fact that so few Americans make a living from agriculture?
Absolutely. We have less than two million farmers, people on the land, according to USDA statistics. In 1900, farmers were 70 to 80 percent of the population.
In the 1960s we had what was called the green revolution, which increased agricultural productivity. And I think people assume that this cycle will continue endlessly, that by using fertilizers and pesticides we can continue to increase farm yields. But when does soil depletion cause that to change?
Technology has been and is being developed that will enable adequate food production without degrading the soil. Obviously, you can go back in history and see many, many examples of failed civilizations and many failures in this country due to soil degradation. A civilization cannot sustain itself without productive soil. But what folks don't understand is that we have made huge strides in this country in technologies to enhance the productive capacities of our soils.
What are some of those advances?
We know now that you can't leave the soil surface bare in environments that are highly erodable. For example, we have a program in the U.S. that pays farmers to take land out of production and put it back into grass. It really has protected soils in the Great Plains, predominantly, from wind erosion. It also provided resources to take highly erodable lands out of areas that are influenced by water erosion. Our experiments throughout the Great Plains show that soils are becoming more productive under those circumstances. The practice of soil tillage leaves crop residues on the surface and can increase productivity.
Is it fairly widespread, the use of covers like that?
It's increasing nationally at fairly decent rates. For instance, in North Carolina in the 1950s and 1960s, the soil was fully tilled before planting. But now we have no-till, which means that soil is not disturbed in the planting and production of a crop. And now in North Carolina, depending on where you are, 30 to 50 percent of the producers are using these methods.
Another big trend obviously is toward organic agriculture. And certainly this should have multiple soil benefits.
There's no question that if organic agriculture incorporates those kinds of technologies in which soils are not disturbed, and are protected from erosive losses of the valuable organic matter, then productivity will be enhanced.
Are you optimistic in the long run that we will preserve our soil health in some of the richest farmland in the world?
Only if we educate our young people so that they understand where food comes from, how it's produced and why soils have to be protected. One issue is degradation of soils, but the other is land use. Many cities were originally established in areas with very high soil productivity. Chicago, for example, was developed because there was a large body of water, and some of the most productive soils on the planet. But Cook County no longer has anything to do with agriculture. And the surrounding counties have been zoned out of farmland, too. And that's the real challenge: we have to figure out a way to have an additional three billion people and still maintain our most productive lands for the purpose of growing food. If we continue to build parking lots and shopping malls on our most productive soils, we're eventually not going to be able to be the agricultural exporter that the U.S. has been in the last century. CONTACT: Soil Science Society of America, (608)273-8080, www.soils.org.
Paul Gleason contributed research to this interview.
RELATED ARTICLE: NRCS: the feds get their hands dirty.
Federal involvement in soil conservation began with a very passionate and motivated soil scientist by the name of Hugh Hammond Bennett, whose career as an agronomist began in 1903 when he joined the Bureau of Soils in the U.S. Department of Agriculture (USDA).
Bennett was hired to conduct soil surveys, which led to his personal conviction that soil erosion was a "national menace" and if left unchecked would disrupt the nation's ability to produce food. His efforts led Congress in 1929 to approve soil erosion experiment stations.
In the 1930s, the Great Depression provided the opportunity to further Bennett's "dirty work" when the National Industrial Recovery Act authorized erosion control efforts. Bennett argued that effective erosion control needed a comprehensive and multidisciplinary approach involving agronomists, engineers, foresters, wildlife biologists and social scientists.
Congress then created the Soil Erosion Service (SES) under the U.S. Department of the Interior, and named Bennett the first director. In his new position Bennett set up demonstration projects to educate communities about the benefits of erosion control. The Civilian Conservation Corps did most of the labor.
In 1935, Bennett found himself once again attempting to persuade Congress that more needed to be done: the dirt problem became a dust problem as once-productive farmlands in the Great Plains morphed into the infamous Dust Bowl. As Bennett testified, he watched the Senators become increasingly bored. But just as he was beginning to lose hope, the sky went dark and a great dust storm descended on the Capitol. The terrifying experience was enough to convince Congress to unanimously pass more soil conservation legislation.
Declaring soil erosion a menace to the national welfare, Congress renamed the SES the Soil Conservation Service (SCS) and granted it broad powers to attack the problem. Following a power struggle, it emerged as a branch of the USDA. In 1937, President Roosevelt worked with the states to create conservation districts with locally elected representatives, allowing for federal assistance without complete centralized control.
Under the Emergency Watershed Program, the agency has assisted many communities in recovery from natural disasters such as Hurricane Andrew and the Oakland-Berkeley Hills fires of 1991. SCS became the Natural Resources Conservation Service (NRCS), which encompasses water, air, plants and animals in addition to soil.
Today there are a number of advocacy groups devoted to soil conservation, such as the Soil and Water Conservation Society and the Land Institute, boasting a diverse membership, including researchers, planners, policymakers, administrators, teachers, students, farmers and ranchers. There is room for everyone to roll up their sleeves and do a little dirty work.
CONTACT: National Association of Conservation Districts, (202)547-6223, www.nacdnet.org; Natural Resources Conservation Service, www.nrcs.usda.gov; Soil and Water Conservation Society, (515)289-2331, www.swcs.org; The Land Institute, (785) 823-5376, www.landinstitute.org.
RELATED ARTICLE: The lay of the land: is soil science a vanishing skill?
By Keith Goyne and peter Motavalli
Randy Miles likes to teach soil science from pits dug deep into the earth. The University of Missouri soil science professor enjoys taking his students into the field, prying clods from the pit face and showing the distribution and properties of soils across Midwestern landscapes. "It's hard for students to understand the fundamental changes in soils over landscapes and make interpretations for land use unless they walk the land and kick the clods," he says.
However, despite his efforts and those of other dedicated practitioners, there are fewer and fewer soil scientists with practical field experience, and that makes it harder for governments to make informed land-use decisions. According to Fred Miller, former director of the School of Environment and Natural Resources at Ohio State University, "Soil degradation and poor soil management undermine the ecological functions that support the very essence of human well-being and sustenance."
The number of U.S. undergraduates majoring in soil science has declined precipitously since the 1970s, and that's a "serious problem," says Mary Collins, president of the Soil Science Society of America. Daniel Fritton of Penn State University estimates that only a quarter to a third as many make that choice as did 25 years ago. "It is a struggle to attract students into the field," says Fritton. Don Post, professor emeritus at the University of Arizona, adds that he sees a decline in field courses, due in part to high costs and "student inconvenience."
Couple the declining numbers of soil science graduates with the fact that 50 percent of soil scientists employed by the U.S. Department of Agriculture (USDA) and the National Resources Conservation Service (NRCS) will retire in the next five to 10 years, and the problem is magnified several-fold. Bill Pauls, NRCS assistant state soil scientist for Missouri, has also observed an overall decrease in the number of field-experienced soil scientists.
As a scientific discipline, soils struggle to be seen as sexy and glamorous. But the people who love it are trying hard to change that impression. Student members of university soil-judging teams coin fun nicknames for themselves, such as "Spodalicious" and "Sexyoxide."
Under the auspices of the National Academy of Sciences, Collins chairs a subcommittee to investigate trends in undergraduate soil science enrollment and explore possible changes. Additionally, universities nationwide are trying various approaches, including offering scholarships to students who study soil science; changing course lectures and field trips to address environmentally related topics; integrating new technologies (computer simulations, geographic information systems, or GIS, and remote sensing) into the classroom; creating environmental science majors that include a soil science emphasis area; and developing internship opportunities with state and federal agencies and private companies.
Fading away are the days when a stalwart soil scientist wandered through forests and fields, focusing solely on mapping uncharted soils. But modern-day soil scientists are better equipped to interpret information for improved environmental management. These new soil scientists will still need to gain practical field experience and learn from the older generation of experts. Our suggestion is to keep one hand on the keyboard and one foot in the soil pit at all times! CONTACT: University of Missouri Department of Soil, Environmental and Atmospheric Sciences, (573)882-6301, www.snr.missouri.edu/seas.
KEITH GOYNE is an Assistant Professor of Environmental Soil Chemistry at the University of Missouri; PETER
MOTAVALLI is an Associate Professor of Soil Nutrient Management at the same school.
TAMSYN JONES is a recent graduate of the University of Missouri at Columbia, currently pursuing further study in Tasmania.
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|Date:||Sep 1, 2006|
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