Farming in Nature's Image: An Ecological Approach To Agriculture
305
Farming in Nature's Image: An Ecological Approach To Agriculture
305Overview
˜Farming in Nature's Image provides, for the first time, a detailed look into the pioneering work of The Land Institute, the leading educational and research organization for sustainable agriculture.
The authors draw on case studies, hands-on experience, and research results to explain the applications of a new system of agriculture based on one unifying concept: that farms should mimic the ecosystems in which they exist. They present both theoretical and practical information, including:
- a review of the environmental degradation resulting from current farming practices
- a critical evaluation of the attempts to solve these problems
- a detailed description of the ecosystem perspective and the proposed new agricultural system
- a case study illustrating how this new system could be applied to temperate grain production using perennial seed crops and the prairie as a model
- an examination of the potential savings in energy and water use, as well as potential contributions to ecological experiments and yield analysis work from The Land Institute.
Written in clear, non-technical language, this book will be of great interest to soil and agricultural scientists, academics, policymakers, environmentalists, and other concerned with finding long-range solutions to agricultural problems.
Product Details
| ISBN-13: | 9781597269049 |
|---|---|
| Publisher: | Island Press |
| Publication date: | 04/16/2013 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 305 |
| File size: | 3 MB |
About the Author
Read an Excerpt
Farming in Nature's Image
An Ecological Approach to Agriculture
By Judith D. Soule, Jon K. Piper
ISLAND PRESS
Copyright © 1992 Judith D. Soule Jon K. PiperAll rights reserved.
ISBN: 978-1-59726-904-9
CHAPTER 1
Ecological Crises of Modern Agriculture
POLLUTION, DEPLETION, DEGRADATION, erosion, contamination, poisoning—these are terms usually associated with heavy industry and cities, not with our green countryside of fields and scattered farmsteads. But these are all terms that are applicable to the environmental problems caused by conventional U.S. agriculture today. Agriculture has become very like traditional manufacturing industries, with many of the same environmental risks and waste-disposal problems among its side effects. This analogy has a dangerous flaw: because of agriculture's extensiveness and its use of toxins that are broadcast into the environment, its impacts are more wide-ranging than those of most other industries. In fact, they are so widespread that they are generally overlooked. This chapter explores the major ecological problems of agriculture: soil erosion, loss of genetic and biotic diversity, depletion of energy and water resources, chemical contamination of water, workers, and food, and creation of new and more serious pest problems. The breadth and seriousness of these problems present strong evidence that current agricultural practices are ecologically unsustainable.
DAMAGE AND DEPLETION
Despite major awareness stirred up by the Dust Bowl of the 1930s, and more than fifty years of research and government-sponsored soil conservation programs, modern agriculture has failed to produce a system that sustains its own capital—the living soil. Each year more topsoil slips away, down the earth's rivers to the sea. With each harvest, more soil is used up than is rebuilt, as, in effect, the soil is mined from farm fields. Likewise, the other pieces of our agricultural resource base—genetic diversity, fossil energy supplies, and water sources—have been damaged or depleted. In North America this exploitative approach produced the bounty that permitted the rapid colonization and development of an affluent society. Now that humankind has colonized the whole earth, however, people can no longer abandon spent fields and just wander off looking for new soil. As a society we must face the price of our wastefulness and the limits of the planet's ecological foundations.
EROSION
On the hopeful side, soil can be improved, even restored, given enough time. Soil-building processes can be enhanced, and remaining soil can be protected from further erosion. It is not a hopeless problem. But for anything to improve, society must first recognize the seriousness and magnitude of the problem.
On the Farm. Soil erosion increased at an alarming rate in the 1970s. Encouraged by booming export markets and federal farm programs, farmers removed shelterbelts, grassed waterways, and terraces so that they could plant fencerow to fencerow. As millions of acres of erosion-prone land were brought into production, erosion rates rose dramatically. In 1977, the Soil Conservation Service (SCS) initiated the National Resources Inventory (NRI) to document just how much soil was washing and blowing away. They found that, on average, the country was losing 1.8 tons of soil per acre (4 metric tons per hectare) in excess of the "officially tolerable" average annual replacement rate ("T") of 5 tons per acre (11 metric tons per hectare).
In 1982, SCS repeated the NRI, using more comprehensive methods, and came up with even gloomier figures. More highly erodible land had been brought into production during the five years between surveys, and the average loss per acre from croplands was now 8 tons per acre (18 metric tons per hectare), or 3 tons (2.7 metric tons) above T. That meant that 3.4 billion tons (3.1 billion metric tons) of soil were being washed or blown away each year. And that occurred in spite of the fact that acreage farmed with conservation tillage, which reduces erosion, nearly tripled during this period.
Although a small proportion of the cropland accounts for most of the erosion, the majority of the cropland is affected at some level. Twenty percent of U.S. cropland is subject to serious erosion, but fully one third (118 million out of 350 to 400 million acres, 48 million out of 142 to 162 million hectares) is classified as "highly erodible land" (HEL) under the conservation provisions of the 1985 farm bill. The HEL designation means that the land is highly vulnerable to erosion when cropped. While the Conservation Reserve Program (CRP) is removing some HEL cropland from production (25.5 million acres, or 10.3 million hectares, of the pool of 118 million acres, or 48 million hectares, as of February 1988), it is not yet clear how effective this has been at reducing erosion. Regions with the largest acreage of HEL cropland had low enrollment in CRP as of February 1988. For example, only 3.6 million acres out of a pool of 19 million acres (1.5 million hectares out of 7.7 million hectares) HEL in the Corn Belt were enrolled.
Tolerated Losses. What do these sobering figures mean in terms of the depth of soil lost, the productivity sacrificed, and, more importantly, the land's sustainability? The first step is to translate soil loss from tons into inches. It is generally recognized that deeper soils can sustain productivity longer than shallower soils. They can withstand more erosion before they will show much loss in productivity. In Iowa, where soils were deep to start with, it took a loss of 10 inches (25 centimeters) of soil to reduce corn yields by 50 percent. On shallow soils in Nigeria, a loss of only 2 inches (5 centimeters) cut corn yields in half. It takes from 300 to 1000 years for an inch (2.5 centimeters) of soil to be formed naturally. When agriculture causes soil loss to proceed much more rapidly than soil building, the system is literally losing ground; it is an unsustainable system.
If you removed the top inch of soil from an acre of land, it would weigh about 160 tons (145 metric tons). That means that at the national average rate of loss of 8 tons per acre (18 metric tons per hectare) each year, an inch of soil from the average acre of cropland is lost every twenty years (or 1 centimeter every 8 years). That may not sound like a particularly dramatic rate of loss, but when compared to the soil formation rate (300 to 1000 years per inch, or 120 to 400 years per centimeter) it becomes obvious that erosion rates are well beyond sustainable loss. Furthermore, erosion is much higher than average in some regions. At the rate of 100 tons per acre (224 metric tons per hectare) that is lost on some slopes (in some years) in the wheat-growing region of the Palouse in Washington State, it would take only 1.6 years to lose an inch of soil. The average acre in this region loses an inch of soil about every twelve years (14 tons per year, or 12.6 metric tons per year), and this has been going on since the 1920s. Soils were originally so deep and rich in that region that erosion seemed to be inconsequential.
The signs in the Palouse that soils are losing productivity are obvious now. The soil on hilltops is now universally paler than that on the slopes, almost all of which have noticeable rills, many even gullies. The crops are thinner on hilltops too. The apparently limitless rich Palouse soil, originally lying to depths measured in feet, is reaching its limit after only 100 years in production. Still, farmers don't perceive the problem to be as severe as USDA guidelines for the CRP would indicate. In one watershed, 84 percent of the land fell into the USDA HEL land class. Yet farmers only estimated that 24 percent of their land was highly erodible.
The major reason for this discrepancy is probably the fact that the land is still highly productive, and productivity remains the major currency of agriculture. Improved crop varieties and increased fertilizer applications have enabled farmers to disguise soil losses. Yet one must wonder what yields would now be if all that soil were still in place. Could the same high yields now be possible with much less added fertilizer, perhaps? One study of those eastern Washington wheat fields concluded that 90 years of soil erosion has robbed the land of 50 percent of its potential productivity.
Costs on the Farm. Not only does a focus on productivity disguise the fact of soil erosion, but it ignores many other costs of erosion. Failing to recognize these other costs causes society to underestimate the cost of erosion and overemphasize the cost of soil conservation. Erosion clearly increases the direct costs of farming. More fertilizer must be applied to compensate for loss of fertility. Other potential costs of erosion include higher fuel and tractor maintenance costs as soils thin, organic content declines, and the heavier, denser subsoil becomes incorporated in the tillage layer. Erosion increases the risks of farming. Crops may be more vulnerable to drought, disease, and insect damage when growing in eroded soil, which is poorer in organic matter. If all these costs were routinely included in farm budgets, soil conservation practices would be much more popular.
In addition to removing soil, erosion changes the physical structure and biological properties of the remaining soil. Fine particles of organic matter are light, concentrated near the soil surface, and thus the first to go when erosion occurs. This means that the remaining soil has reduced nutrient-holding and water-holding capacity and supports a poorer living soil community. As water-holding capacity declines, soil is less able to absorb rainfall, and more rain runs off the surface. This causes erosion to accelerate. Erosion thus disrupts the natural processes that allow organic matter to accumulate in the soil and to hold soil in place and that perpetuate soil-building processes, while it sets in motion processes that only make the problems worse. The longer erosion is allowed to occur, the faster it will occur, until this waste of "capital" bankrupts a precious resource.
Costs Off the Farm. Significant consequences of erosion occur off the farm as well. Eroded soil is a nuisance, even a hazard, where it is deposited. Reservoirs commonly catch huge volumes of such soil. There the deposition interferes with municipal water supplies and recreational potential. In the United States, 1.4 million acre-feet (0.17 million hectare-meters) of reservoir and lake capacity are lost to sedimentation each year. Dredging to remove sediments is expensive and creates its own problem: what is to be done with all that sludgy material? Municipal water systems bear the brunt of this dilemma, and thus a farm problem becomes an urban problem as well.
Erosion from cropland is the single largest source of nonpoint pollution in the United States, producing about 50 percent of suspended sediments. Sediments interfere with the breeding and feeding of aquatic species, destroying fish, mussels, and benthic insect populations. The problem is compounded when sediments carry nutrients or pesticides with them. Nutrient-enriched waters support algal blooms, reduced oxygen supplies, and rapid aging of lakes.
Flooding also follows erosion, for as the soil's water-holding capacity diminishes, run-off increases, and streams receive more water to carry. At the same time, the sediment loads carried off fields are deposited in riverbeds and wetlands (nature's sponges). As these streams and wetlands become filled with sediments, both the watershed's capacity to hold excess water, and the rivers' capacity to carry it away, diminish. This combination greatly increases the frequency and severity of flooding. Erosion disrupts the natural moderating systems of watersheds and sets into motion processes that are self-accelerating.
Water-caused erosion is not the only problem. Soil particles carried by wind are a significant source of air pollution. Wind erosion accounts for some 33 million to 239 million tons (30 million to 217 million metric tons) of airborne particulates annually. Even the low estimate is larger than the 20-million-ton (18-million-metric-ton) contribution of smokestacks and other point sources. In dry regions, such as the Great Plains, wind erosion is the primary form of soil erosion.
Modern agricultural practices also destroy soil in other ways besides eroding it away. Irrigation can be very destructive to soil, particularly in arid regions. Waterlogging, salinization, and alkalinization have damaged about half of the world's irrigated lands. Once salinization has proceeded to the point that a salty, white crust covers the soil surface, the land becomes unfit for cultivation and can only be reclaimed by extremely expensive procedures. In arid regions, soil and groundwater are typically high in salts, natural drainage is poor, and evaporation is high. With this combination of features, irrigation is a sure formula for land damage. Poor drainage of irrigation water allows water tables to rise and soil to become waterlogged in the crop root zone. Salty groundwater can then seep through unlined irrigation canals to reach the surface, where it evaporates and forms a crust on the soil surface. These problems occur wherever large acreages of cropland are irrigated—from Pakistan to the San Joaquin Valley in California.
Future Costs. Projections of future consequences of current erosion trends range from the absurdly optimistic view that modern technology is freeing humankind from the need for soil anyway, to the gloomier statistic that at current rates 5 hectares of cropland are destroyed each minute by erosion, worldwide. This amounts to a loss of 3.3 percent of cropland worldwide (3 percent in the United States alone) by the year 2000 (based on 1975 cropland acreage). In Family Farming, Marty Strange projects that a continuation of 1980 erosion rates for fifty years would reduce U.S. yield by the equivalent of a loss of 23 million acres (9.3 million hectares). Another estimate for the United States predicts that productivity losses due to erosion over the next fifty years would be equivalent to the loss of 8 percent of the total base cropland. Given a base of 350 million to 400 million acres (142 million to 162 million hectares), this amounts to 27 million to 32 million acres worth of productivity lost (equivalent to 11 million to 13 million hectares). Set against an expected worldwide population increase of more than 50 percent over the same time span, even a 3 percent loss of farmland should be considered intolerable, especially when it is a preventable loss.
The USDA is counting on a combination of retiring highly erodible land into the CRP and disguising productivity losses on the remaining land with new technology. They project that, given another hundred years of 1982 erosion rates, more than half the crop acreage would lose only 2 percent of its productivity and that this could easily be countered with improved crop varieties, additional fertilizer, etc. The trouble is that the CRP was set up for only a ten-year span, and thinking in terms of a hundred years is still rather shortsighted. To achieve sustainable production, society must learn to think in terms of maintaining the land's productive potential indefinitely.
Despite disagreement on the importance of current erosion rates, most scientists agree that the more land that is brought under cultivation, the more erosion will occur, unless methods change. This is because the best, least erosion-prone lands are already being cultivated. New farmland will be less suited to cultivation and more highly erodible.
LOSS OF GENETIC DIVERSITY
One of the dominant themes of modern agricultural development has been reduction in diversity. This is seen in crop and livestock breeding, where the genetically narrow varieties and breeds that now dominate agriculture have replaced a multitude of locally adapted strains. It is also apparent in cropping systems, as the acreage in continuous monoculture has increased at the expense of acreage in rotation and mixed culture. Even at the global landscape level, conversion of diverse ecosystems to modern-style monocultures reduces the genetic diversity of the earth. Yet diversity is the currency of adaptation. Without it, humans lose the ability to adapt crops and livestock to changing conditions. Likewise, the ecosphere—the living "skin" of the earth—is handicapped in its ability to adapt to change and to remain vital when diversity declines. Declining genetic and species (biotic) diversity threatens the sustainability of agriculture and the resiliency of the ecosphere.
(Continues...)
Excerpted from Farming in Nature's Image by Judith D. Soule, Jon K. Piper. Copyright © 1992 Judith D. Soule Jon K. Piper. Excerpted by permission of ISLAND PRESS.
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Table of Contents
ForewordPreface
Introduction
Chapter 1. Ecological Crises Of Modern Agriculture
Chapter 2. Roots Of The Crises
Chapter 3. An Ecological Perspective On Sustainability
Chapter 4. A New Agricultural Perspective: The Case For Ecological Agriculture
Chapter 5. The Feasibility Of A Prairielike Agriculture
Chapter 6. Culturing Sustainability
Notes
Bibliography
Index