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Toward Sustainable Agricultural Systems in the 21st Century 1 Understanding Agricultural Sustainability Agriculture worldwide faces daunting challenges because of increasing population growth and changing food consumption patterns, natural resource scarcity, environmental degradation, climate change, and global economic restructuring. Yet, at the same time, there are unprecedented hopeful changes and opportunities for the future, including a remarkable emergence of innovations in farming practices and systems and technological advances that have generated promising results for improving agricultural sustainability and an increase in consciousness and concern by consumers about the sources of their food and how it is produced. One of the first comprehensive reports on the scope and importance of systems approaches to improve sustainability of agriculture was documented in the National Research Council report Alternative Agriculture (1989b). The report analyzed and described the economic and environmental results of agricultural practices that could improve sustainability being developed and used by a small subset of U.S. farmers in the second half of the 20th century, and it helped to legitimize an approach to agricultural-systems research that had previously been considered nonscientific. Many so-called alternative practices at that time (integrated pest management, no-till farming, and cover crop planting) are now used by some farmers in mainstream agriculture. Despite the potential benefits of farming practices and systems that improve sustainability, their adoption is far less widespread than society might want. One reason for the low rate of adoption is because of social, economic, and policy incentives that discourage fundamental changes in farming systems. Another reason is that some of those practices have tradeoffs so that they might provide benefits in one aspect and negative consequences in another. The movement toward improved sustainability could be hampered by society’s lack of common agreement on which objectives are the highest priority and how tradeoffs should be managed. Since Alternative Agriculture was published, many changes have been made in how farmers farm. While incremental approaches offer movement toward sustainability, such approaches might not tackle fundamental problems. Systemic changes and multiple paths will also need to be pursued. Indeed it can be argued that sustainability is the process of
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Toward Sustainable Agricultural Systems in the 21st Century constantly adapting farming or food systems to meet clearly articulated and desired outcomes in a robust and resource-efficient manner that also reflects social responsibility. PURPOSE OF THIS REPORT With the support of the Bill and Melinda Gates Foundation and the W.K. Kellogg Foundation, the National Research Council convened a committee to study the science and policies that influence the adoption of farming practices and management systems designed to reduce the costs and unintended consequences of agricultural production. (See Box 1-1 for the statement of task.) To address the statement of task, the committee solicited input from many experts in academia and federal agencies in a series of open meetings and workshops, in addition to drawing on members’ expertise. Two sets of case studies were used to examine farming systems that address those concerns and to explore the factors that affect their implementation, economic viability, and success in meeting environmental and other goals of sustainability. This report reviews the state of knowledge on farming practices, technologies, and management systems that have the potential to improve the environmental, social, and economic sustainability of agriculture and discusses the tradeoffs and risks that might present themselves if more farms were to adopt those practices, technologies, and systems. The report also identifies knowledge gaps in improving agricultural sustainability and makes recommendations for future actions aimed at improving agricultural sustainability. BOX 1-1 Statement of Task The National Research Council Committee on Twenty-First Century Systems Agriculture was tasked to: Provide an overview of the current state of U.S. agriculture in the domestic and world economies, and describe major challenges to farmers and problems in agricultural production related to the environmental, social, and economic sustainability of agriculture. Review the state of knowledge on farming practices and management systems that can increase the environmental, social, and economic sustainability of agriculture. Identify factors that influence the adoption of farming practices and systems that contribute to the goals of increasing agricultural sustainability. Provide an update to the 1989 report’s methodology to compare the productivity and economics of different systems and practices at levels of increasing complexity (from the level of individual components in a farm, to a whole farm, to a regional level). Describe and analyze several case studies (including some from the 1989 report) that illustrate farming practices and management systems that pursue greater agricultural sustainability. Include general information about the operation, features of the management systems being used, and indicators of productivity, environmental, and financial performance. For case studies from the 1989 report, include a retrospective review of the past performance and the evolution of decision making by those producers over time. Recommend research and development needs for advancing a systems approach to farming in the United States, and suggest ways to strengthen federal policies and programs related to improving agricultural production. Evaluate the transferability of principles underlying farming systems and practices that could improve sustainability of different agricultural settings, and develop supportable conclusions and recommendations to improve the sustainability of agriculture under different natural, economic, and policy conditions in different regional or national settings.
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Toward Sustainable Agricultural Systems in the 21st Century Sustainability in agriculture is a complex and dynamic concept that includes a wide range of environmental, resource-based, economic, and social issues. The committee’s definition of sustainable farming does not accept a sharp dichotomy between unsustainable or sustainable farming systems because all types of farming can potentially contribute to achieving different sustainability goals and objectives. Ultimately, the committee believes that sustainability is best evaluated against a range of environmental, economic, and social goals that reflect the views of diverse groups in society. The most intense controversies about the relative sustainability of different farming practices or farming systems necessarily take place within the domain of politics because preferences for particular farming systems reflect the priorities of various stakeholders with different working definitions of sustainability. Although a final assessment of the sustainability of any particular farming practice or system is a social and political act, the committee believes that public debates about improving the sustainability of U.S. agriculture need to be based within a good understanding of the existing scientific research. Science documents the performance and impacts of different agricultural practices and systems, predicts outcomes likely to result from the use of different systems, develops indicators to measure progress toward sustainability goals, and expands the range of technological tools and farming management approaches available. The issue of water quality illustrates the critical role science plays. Societal concerns about water quality led to passage of the Clean Water Act, which has resulted in various local, state, and federal guidelines that require use of “best management practices.” Guidelines are provided for acceptable soil phosphorus upper limits, soil erosion rates, water conservation, tillage practices, pesticide use, and a wide array of other process-type practices, all of which were determined through extensive scientific research. This chapter first defines key terms used in later chapters and then discusses concepts of agricultural sustainability. It identifies the boundaries, or scope, for the overall science assessment of sustainability. Ultimately, this report focuses on current scientific evidence about the performance of farming practices and systems that can contribute to moving U.S. farming systems along a trajectory toward meeting various sustainability goals. Indicators that can be used to provide quantitative assessment of progress toward sustainability are also discussed. The structure of the report is outlined at the end of this chapter. FARMING AND AGRICULTURE General Definitions The terms “farming,” “agriculture,” and “farming systems” can comprise a diverse range of activities. The definitions of agriculture used in the National Research Council (NRC) report Investing in Research: A Proposal to Strengthen the Agricultural, Food, and Environmental System (NRC, 1989a) provide some useful definitions and underscore the potential breadth of farming-related activities and goals (Box 1-2). Various crop and livestock enterprises on individual farms can interact in complex ways with one another and with their surrounding ecosystems (USDA-CSREES, 2007). Combinations of different activities can generate properties of system behavior that might not be understood or predicted by looking at each practice individually. That behavior is manifested at various scales ranging from the field, whole farm, landscape, watershed, and region. Moreover, every farm is embedded in a particular biophysical environment that provides opportunities and constraints for using different practices or management strategies, which shapes the impacts of farming activities on environmental, economic,
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Toward Sustainable Agricultural Systems in the 21st Century BOX 1-2 General Definitions Agriculture encompasses the entirety of the system that grows, processes, and provides food, feed, fiber, ornamentals, and biofuel for the nation. Agriculture includes the management of natural resources such as surface water and ground water, forests and other lands for commercial or recreational uses, and wildlife; the social, physical, and biological environments; and the public policy issues that relate to the overall system. All activities, practices, and processes of the public and private sectors involved in agriculture and forestry are contained within the system. (Adapted from Investing in Research: A Proposal to Strengthen the Agricultural, Food, and Environmental System [NRC, 1989a]). A farm is most correctly used to mean a single, identifiable operational unit that manages natural resources such as water, forests, and other lands to provide food, feed, fiber, ornamentals, energy, and a range of environmental and other services. “Any operation that sells at least one thousand dollars of agricultural commodities or that would have sold that amount of produce under normal circumstances” is considered a farm by the U.S. Department of Agriculture (USDA) (USDA-ERS, 2008). Every farm is embedded within a temporal and spatially dynamic context (environment) and interacts with the geophysical, biological, economic, and social variables of that environment. Farms employ a wide range of production techniques and strategies known as “farming practices.” Farms also use marketing techniques and strategies. A farming system is the mix of crops or animal components, or some combination thereof in a farm, their arrangement over space and time within the farm, the resources and technologies used in their management, and the nature and effectiveness of hierarchical relationships both within the farm and with the ecological, social, economic, and political environments within which it operates. The farming system thus includes community linkages, market integration, labor relationships, and interaction with a wide array of other influencing factors. A farming system type can be defined by any commonalities that one might wish to specify—for example, rangeland, dryland, irrigated, dairy, field crop, high-value crop—and includes the broad range of context-specific farming systems within the type. Food systems and agrifood systems refer to the complex set of actors, activities, and institutions that link food production to food consumption. Studies of agrifood systems often use a “commodity chain” approach, where they examine the production, processing, trade, wholesaling, retailing, and consumption of particular commodities, as well as the upstream and downstream processes that connect the various links in the chain. These terms differ from farming system in that the primary focus is beyond the farm gate. Systems agriculture is used to define an approach to agricultural research, technology development, or extension that views agriculture and its component farming systems in a holistic way. The approach treats components and processes within and across hierarchical levels and scale with appropriate context, and gives major importance to interactions among them. The USDA Cooperative State Research, Extension, and Education Service (CSREES) defines its agricultural systems approaches as follows: “Agricultural enterprises—crop or livestock—deal with such concepts as labor supply, marketing, finances, natural resources, genetic stock, nutrition, equipment and hazards. Although it is possible to effectively manipulate each mechanism of successful farming individually, better results can often be obtained by treating the farming operation as a system. The interactions, then, among system components might be more important than how each component functions by itself. Treating production operations holistically offers greater management flexibility, provides for more environmentally and economically sound practices, and creates safer and healthier conditions for workers and for farm animals.” SOURCE: USDA-CSREES (2007). and social outcomes. This committee also recognizes that farms operate within a complex market, policy, and community context, and interactions with those institutions and social systems affect the performance of every type of agricultural system. Because of the complex interactions at various scales, this committee has chosen to cast a relatively wide net in its assessment of the performance of different farming practices and
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Toward Sustainable Agricultural Systems in the 21st Century systems. The ensuing chapters discuss the impact of individual farming practices not only as individual components of a particular farm enterprise, but also in the context of whole farming systems and as pieces of a larger farming landscape at the watershed, regional, or national scale. Although this report discusses how farmers might be affected by opportunities and constraints created by the larger agrifood system (see Box 1-2), a detailed assessment of the overall social, economic, and environmental performance of the food processing, distribution, and retailing sectors is beyond the scope of this report. Farming Practices and Systems At the time that the report Alternative Agriculture (NRC, 1989b) was released, the term “alternative agriculture” was commonly used to refer to farming approaches (most notably, organic farming) that appeared to be dramatically different from the dominant or “conventional” farming systems that characterized contemporary crop and livestock production in the United States. Today such alternatives are more likely to be referred to as “sustainable” farming, but the phrase is unfortunately ambiguous. Not only do farming enterprises reflect many combinations of farming practices, organization forms, and management strategies, but also all types of systems can potentially contribute to achieving various sustainability goals (for individual farmers and for resource use and environmental sustainability at the landscape scale). At some level, the distinctions between what some call “conventional” agricultural systems and a range of alternative systems have some basis in empirical reality in the U.S. context. The characteristics and examples of practices associated with each system are summarized briefly in the following sections to clearly define those terms and how they are used in this report. Conventional and Industrial Agricultural Systems Conventional agricultural systems draw from a set of predominant farming practices in the United States, although conventional farms are diverse in what they produce and in the specific combination of practices they use. The size of farms using conventional production methods ranges from small to large. Most agricultural commodities in the United States are produced in conventional agricultural systems. Conventional crop production makes use of synthetic pesticides and herbicides, and supplements nutrients generated on the farm (manure) with synthetic fertilizer to maintain soil fertility. Fields are more frequently planted in few rotations of marketable crops than left fallow or planted with cover crops. Conventional corn, soybean, and cotton farms are increasingly planted with seeds that are genetically engineered to facilitate weed control or to reduce pest losses (and pesticide use). Conventional animal production varies depending on the species produced, the size of livestock inventories, and the amount of cropland or pasture available per animal unit. Animals might be housed in partial to full confinement structures, with beef cattle, sheep, and goats being less confined (for at least part of their life cycle), dairy cows being more confined than sheep and beef cattle, and conventional hogs and poultry most confined among livestock. Although beef cattle, sheep, and goat farms rely heavily on pastures, most conventionally raised dairy cows, hogs, and poultry receive virtually all their feed from harvested forage and grain crops raised on the farm or purchased from other farmers. Depending on the number of
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Toward Sustainable Agricultural Systems in the 21st Century animals and the resources of the producers, vaccines, antibiotics, medicated feeds, and growth hormones could be used in production. Animal manure is spread on fields or managed in lagoons, with excess liquid sprayed on fields as in the case of some hog farms. Industrial crop and animal production is a term that has come to be associated with operations that, generally speaking, are characterized by large size combined in some cases with a high degree of specialization. Producers of industrial scale are more likely to produce under contract with food processors and handlers. Animals are more likely to be grown in confined housing, with no pasture in the case of swine and poultry, or with portions of the animal life cycle on pasture or low confinement for dairy and beef animals. Feed is more likely to be a purchased input, rather than produced on the farm, than operations of smaller scale. Many of the larger operations likely have cropped land for liquid manure application, but loading limits over time rarely allow long-term stability for adequate disposal or low-rate application for efficient use of water and nutrients. Contract arrangements often are used for distant application of manure. Industrial farms typically operate at a scale that allows for more extensive division of labor and the use of capital intensive machinery and buildings. They more often rely on a hired workforce than do their smaller-scale counterparts. Over the last few decades there has been a major effort to develop new management approaches and farming practices that not only improve the economic performance and productivity of conventional and industrial farming systems, but also prevent and mitigate their potentially negative effects on soil erosion and water quality, some of which also can improve the economic performance and productivity of conventional farming. Examples of practices used in these strategies are summarized in Box 1-3 and will be discussed in depth in Chapter 3. Ecologically Based Farming Systems Some farming approaches have been developed, at least in part, to respond to perceived problems associated with conventional farming. They represent a concerted departure from some of the key features of conventional farming such as the reliance on off-farm and synthetic inputs. Such approaches emphasize the use of natural processes within the farming system, often called “ecological” or “ecosystem” strategies, which build efficiency (and ideally resilience) through complementarities and synergies within the field, the farm, and at larger scales across the landscape and community. Examples of such systems include organic and biodynamic farming (Box 1-4), although “pure” forms of each system are difficult to identify. Like conventional farms, the specific practices used could vary widely from farm to farm, and often include combinations of the practices discussed in Box 1-3. A Farming Systems Continuum A dichotomy between “ecologically based” and “conventional” farming systems has been a component of public debates over the performance of the U.S. farming sector for several decades. The dichotomy has been a heuristic device that scientists use to explore the comparative performance of different farming systems. However, in reality, these terms are to be used with great caution because farming enterprises found in the United States clearly reflect a potentially infinite set of combinations of particular farming practices, organizational forms, and management strategies. (See the case studies in Chapter 7.)
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Toward Sustainable Agricultural Systems in the 21st Century BOX 1-3 Examples of Practices Designed to Improve Environmental Performance of Conventional Agriculture Crop rotation, which involves the successive planting of different crops on the same lands in sequential seasons to improve soil fertility and to avoid the build up of pathogens and pests that often occur when one species is continuously cropped. The most common rotations involve alternating production of corn and soybean. Cover crops as part of a crop rotation, which involves the planting of crop varieties that can potentially protect fields from soil erosion, suppress weeds, and enhance soil organic matter and nutrient levels. Reduced-tillage and no-till practices, in which a crop is planted directly into a seedbed not tilled since harvest of the previous crop. Instead of plowing soil and burying crop residues, no-till farmers minimize soil disturbance and leave residues on the surface of their fields after harvest. Integrated pest management (IPM), which involves the strategic use of complementary practices—including cultural, mechanical, biological, ecological, and chemical control methods—to keep pest levels below critical economic thresholds. Precision farming practices, which combine detailed spatial information about soil conditions and indicators of crop performance to target fertilization and other crop management practices where they are most needed. Diversification of farm enterprises, which helps increase biodiversity, control pests and diseases, and reduce risks from climatic and market volatility. Other agricultural conservation best management practices (BMPs), which are recommended as part of federally funded conservation programs. BMPs include the use of buffer or filter strips, riparian area access management, manure handling and management, nutrient management planning, wildlife habitat enhancement within agricultural landscapes, composting to process agricultural wastes, and practices designed to increase irrigation water use efficiency (USDA-NRCS, 2009). The development of crops and animals that have enhanced genetic resistance to climatic extremes, pests, and other threats, often with the use of new genetic engineering tools. BOX 1-4 Examples of Ecologically Based Farming Systems Organic farming systems emphasize the use of renewable resources and the conservation of soil and water to enhance environmental quality for future generations. They typically rely on crop rotations, green manures, composts, naturally derived fertilizers and pesticides, biological pest controls, mechanical cultivation, and modern technology. Organic meat, poultry, eggs, and dairy products come from animals that are not given any antibiotics or growth hormones. Organic food is produced without the use of most conventional pesticides, fertilizers made with synthetic ingredients or sewage sludge, bioengineering, or ionizing radiation. Before a product can be labeled “organic” in the United States, a government-approved certifier inspects the farm where the food is grown to make sure the farmer is following all the rules necessary to meet USDA organic standards. Biodynamic farming systems typically use the full range of organic production practices, but also use a series of eight soil, crop, and compost amendments, called preparations, made from cow manure, silica, and various plant substances. Biodynamic farming also places greater emphasis on (1) the integration of animals to create a closed nutrient cycle, (2) using an astronomical calendar to determine auspicious planting, cultivating, and harvesting times, and (3) an awareness of spiritual forces in nature. Biodynamic farmers view the soil and the whole farm as an integrated, living organism and self-contained individuality. More than a production system, biodynamic agriculture is a practice of living and relating to nature in a way that focuses on the health of the bioregion, landscape, soil, and animal, plant, and human life, and it promotes the inner development of each practitioner. The Demeter Association has certification programs for food and feed produced by strict biodynamic farming methods in different countries.
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Toward Sustainable Agricultural Systems in the 21st Century Moreover, the definitions that once clearly demarcated conventional from ecologically based farming systems have become muddled. One example is the “conventionalization” of the organic farming industry in the United States (Guthman, 2004), characterized by the entry of large-scale farms in the market for USDA-certified organic products. Most farms present examples of hybrid or intermediate stages on a continuum between the extremes of agricultural practices, and their adoption of various new practices has produced apparent gains in environmental performance (Keystone Center, 2009). Some of the “mixed farming systems” also have been given names (Box 1-5). The committee concludes that no simple typology or set of categories can capture the complexity of the farming practices and systems used on diverse U.S. farms. The lack of a single accepted typology complicated the writing of this report. Because so much of the research literature is based on comparisons of particular farming practices, or of one or more of those stylized “farming systems,” research findings are cited throughout the report using the categories described by the scientists who conducted the research. For this reason, this report cites organic farming systems more frequently than other ecologically based systems. The illustrative use of organic systems is not intended to imply that organic BOX 1-5 Examples of Mixed Farming Systems Conservation agriculture is a term used by the United Nation’s Food and Agricultural Organization (FAO) to refer to the use of resource-conserving but high-output agricultural systems. According to the FAO, conservation farming typically involves the integrated use of minimal tillage systems, cover crops, and crop rotations (http://www.fao.org/ag/ca/). Reduced- or low-input farming is based on a reduction of materials imported from outside the farm, such as commercially purchased chemicals and fuels. Low-input farming employs technologies and is structured in such a way that tightens flow loops and provides ecosystem services internal to the farm and field, and therefore reduces input use. Such internal resources include biological pest controls, solar or wind energy, biologically fixed nitrogen, and other nutrients released from green manures, organic matter, or soil reserves. Whenever possible, external resources are replaced by resources found on or near the farm. Many reduced-input or low-input farming systems are examples of integrated farming systems (see below). Integrated farming system is a term commonly used in Europe to describe widely adopted production systems that combine methods of conventional and organic production systems in an attempt to balance environmental quality and economic profit. For example, integrated farmers build their soils with composts and green manure crops but also use some synthetic fertilizers; they use some synthetic or natural pesticides in addition to biological, cultural, and mechanical pest control practices. Alternative livestock production systems refer to farms that use lower-confinement housing and rely more on pastures than conventional and industrial livestock farms. A common example in dairy farming is the use of intensive rotational grazing practices that involve the use of short duration, intensive grazing episodes followed by long rest periods that allow pastures or fields to recover. Mixed crop-livestock farming is characterized by livestock enterprises where a significant fraction of the animal feed inputs are generated on cropland and pastures that are under the direct control of the livestock farmer. Those systems capitalize on the ability of the enterprise to use synergies between the crop and livestock enterprises to efficiently recycle nutrients, promote crop rotations, and insulate livestock farmers from price fluctuations in feed and input markets. They reflect the resurgence of traditional mixed crop-livestock farming systems that characterized most production units in the first half of the 20th century. On the other hand, the scale and sophistication of many 21st century mixed crop-livestock farms reflect the effects of new technologies, breed improvements, and greater awareness of environmental issues than their predecessors.
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Toward Sustainable Agricultural Systems in the 21st Century farming systems are more sustainable than other farming systems. Indeed, all farming system types have opportunities to improve in sustainability, and all farming system types could be unsustainable depending on their management and on environmental, social, and economic changes over time. AGRICULTURAL SUSTAINABILITY Defining Sustainability Goals In its broadest sense, sustainability has been described as the ability to provide for core societal needs in a manner that can be readily continued into the indefinite future without unwanted negative effects. Most definitions of sustainability are framed in terms of three broad social goals: environmental, economic, and social health or well-being.1 For example, a sustainable farming system might be one that provides food, feed, fiber, biofuel, and other commodities for society, as well as allows for reasonable economic returns to producers and laborers, cruelty-free practices for farm animals, and safe, healthy, and affordable food for consumers, while at the same time maintains or enhances the natural resource base upon which agriculture depends (USDA-NAL, 2007). The legal definition of sustainable farming systems as defined in the Food, Agriculture, Conservation, and Trade Act (1990 Farm Bill and revised in 2007) is a useful starting point for identifying sustainability goals for the purposes of this report: an integrated system of plant and animal production practices having a site-specific application that will, over the long term: satisfy human food and fiber needs; enhance environmental quality and the natural resource base upon which the agricultural economy depends; make the most efficient use of nonrenewable resources and on-farm resources and integrate, where appropriate, natural biological cycles and controls; sustain the economic viability of farm operations; and enhance the quality of life for farmers and society as a whole. This legal definition mingles a description of societal sustainability goals with strategies that can be used to achieve those goals (for example, “an integrated system which will use, where appropriate natural biological cycles and controls”; or “make the most efficient use of nonrenewable and on-farm resources”). This report makes a clear distinction between societal sustainability goals and the management systems used to pursue these goals. That distinction recognizes that the same goals can potentially be achieved through a range of different management and organizational approaches. Modifying the Farm Bill definition slightly, the committee isolated four key societal sustainability goals that serve as the organizing principles for the remainder of this report (Figure 1-1): Satisfy human food, feed, and fiber needs, and contribute to biofuel needs. Enhance environmental quality and the resource base. Sustain the economic viability of agriculture. Enhance the quality of life for farmers, farm workers, and society as a whole. The sustainability of a farming practice or system could be evaluated on the basis of how well it meets various societal goals or objectives. To be sustainable, a farming system needs 1 In Europe, the three goals of sustainability are sometimes referred to as the 3Ps: people, prosperity, and planet, or, alternatively, as the “triple bottom line.”
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Toward Sustainable Agricultural Systems in the 21st Century FIGURE 1-1 Sustainability goals used in this report. The area where the four goals overlap represents the highest sustainability in the continuum. to be robust (that is, be able to continue to meet the goals in the face of stresses and fluctuating conditions; to adapt and evolve), be sufficiently productive, use resources efficiently, and balance the four goals. There are, however, often tradeoffs or synergies among the various goals and their related objectives, toward which sustainability is directed. In the discussions that follow, the scientific evidence surrounding different farming practices or farming systems that illustrate their ability to further each of these four societal goals is discussed. The committee is not suggesting or implying that a farming practice would have to simultaneously accomplish each of these goals to be considered “sustainable.” Rather, it recognizes and expects that combinations of practices used in a system will affect each of the four goals in different and often complicated ways. A sustainable system would balance and meet each of the four goals to a large extent. Objectives Each of the four sustainability goals consists of a large number of more specific objectives that represent different paths toward achievement of the goal. For example, the goal to “satisfy human food, feed, and fiber needs” requires managing farming systems in the aggregate so that there will be enough affordable food and fiber (including for energy production) in the future for all on the globe, although U.S. production would only play a part in overall global production. That goal has a long history and is a fundamental concern of all societies through time and can be summarized with the crucial question: Will there be sufficient agricultural resources in the future? Achieving that goal will, at a minimum, require sufficient productivity (for example, the sheer volume of outputs produced from a given agricultural activity), farming practices that produce the outputs at a price that consumers can afford, and marketing and distribution systems to ensure that people have ready access to farm products. The concepts of productivity, affordability, and access represent specific objectives that are required to meet the overall goal. Even relatively simple objectives can quickly become more complex. For example, agricultural productivity over time is influenced by the technologies that are available.
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Toward Sustainable Agricultural Systems in the 21st Century Sometimes built capital, such as machinery or chemicals, can substitute for natural capital, such as natural soil fertility. Food productivity has risen over time in the United States, in part, because of the substitution of fertilizers for natural soil fertility. If the substitution is viewed as socially acceptable, if fertilizer is affordable and effective, and if its use is not accompanied by unwanted or detrimental side effects, then the loss of natural soil fertility as a result of a farming practice might be viewed as sustainable. If, however, fertilizer is viewed as a poor substitute for natural fertility, as having important unwanted side effects, or is thought to be unaffordable or ineffective in the future, then a farming system that results in losses of natural fertility of the soil will be viewed as unsustainable (Batie, 2008b). Likewise, each of the other three goals comprise a number of specific objectives. The objectives listed in Box 1-6 are representative of various objectives associated with sustainability goals, and they are used to organize the review of the scientific literature in Chapters 3, 4, and 5. The specific objective of access to food is not discussed in this report because it is covered by another report, The Public Health Effects of Food Deserts: Workshop Summary (IOM and NRC, 2009). Quality and safety of food output is discussed in the context of its quality and safety at the farm gate. Food processing is beyond the scope of this report. As the representative objectives listed in Box 1-6 illustrate, the question of the sufficient quantity of agricultural resources is not the only societal concern underlying calls for more sustainability. For example, the objectives listed with respect to environmental quality reflect a societal concern about the impacts of agriculture on the functional integrity of envi- BOX 1-6 Representative Objectives Associated with Sustainability Goals Satisfy human food, feed, and fiber, and contribute to biofuel needs Productivity of farming practice or system Quality and safety of food output Affordability of farm outputs Availability of farm outputs Enhance environmental quality and quality of resource base Soil quality and health Water quality Air quality Biodiversity Animal health and welfare Sustain the economic viability of agriculture Farm business profitability and viability Farm and household viability Farm labor economic security Community economic security Enhance the quality of life for farmers, farm workers, and society as a whole Ensure that farm operators and their households are able to maintain an acceptable quality of life, including access to health and retirement benefits Protect the health and welfare of farmers, farm workers, and society Enhance community or social well-being from the surrounding agriculture, including access to local food, sustained provision of ecological services, and maintenance of attractive landscapes
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Toward Sustainable Agricultural Systems in the 21st Century in the “honest broker” spirit that this committee undertook to review the various scientific (social and biophysical) literature on sustainable farming systems. In 1999, the National Research Council’s Board on Sustainable Development observed that the “quest for sustainability will necessarily be a collective, uncertain and adaptive endeavor in which society’s discovering of where it wants to go and how it might try to get there will be inextricably intertwined” (NRC, 1999, p. 17). That is, sustainability will be discovered and more clearly defined for agriculture as society experiments with different farming systems and observes their consequences relative to sustainability goals and makes legal, institutional, and management adjustments in response. In that sense, sustainable management of agricultural resources is a journey of discovery and adaptive management, more than a specific destination. This committee, thus, regards sustainability as more of a process that moves farming systems along a trajectory toward meeting various socially determined sustainability goals (that is, desired outcomes) as opposed to achieving any particular end state. Sustainability goals and strategies used to achieve them are expected to change over time as more is learned about tradeoffs and societal objectives, and as biophysical or socioeconomic conditions change. For the remainder of this report, those assumptions are used to guide the scientific review to identify what attributes a farming systems needs to exhibit to be sustainable (that is, to put agriculture on a sustainable trajectory overtime). INDICATORS OF SUSTAINABILITY Evaluation of progress toward sustainability in agricultural systems inevitably requires monitoring of some set of measurements or indicators. The National Research Council’s report, Our Common Journey; a Transition Toward Sustainability, noted the importance of appropriate monitoring and indicator systems, with indicators being “repeated observations of natural and social phenomena that represent systematic feedback. They generally provide quantitative measures of the economy, human well-being, and impacts of human activities on the natural world” (NRC, 1999, pp. 233–234). Indicators are used to represent or serve as proxies for the impacts or outcomes of concern. In the policy arena, indicators can be used to inform the design and implementation of programs and policies. Figure 1-2 provides an example of the use of indicators in an adaptive management framework to pursue the broad goal to “enhance environmental quality and the quality FIGURE 1-2 Adaptive management for sustainability of agricultural farming systems.
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Toward Sustainable Agricultural Systems in the 21st Century of resource base.” An example of a specific objective within that goal could be to improve water quality, which might then be narrowed to one particular water quality concern, such as nitrogen runoff from corn production that is thought to contribute to hypoxia conditions in the Gulf of Mexico. Decision makers could use information from indicators that directly or indirectly approximates nitrogen runoff by assessing the area where particular agricultural practices or farming systems are present. Policy actions could then be based upon an evaluation of the effectiveness of behavioral changes on nitrogen loading into the Mississippi River and a multilevel spatial assessment to target efforts in what are found to be the most critical areas. Indicators of sustainability presume the existence of goals and objectives, and yet there is no guarantee that all parties will agree on which sustainability objectives and goals are desirable or most important, particularly if tradeoffs are involved. As argued previously, the choice and priority of different goals, and hence use of different indicators, require a political process involving multiple stakeholders to best serve society. Indeed the authors of the 1999 NRC report concluded “that there is no consensus on the appropriateness of [a single] … set of indicators or the scientific basis for choosing among them” (NRC, 1999, p. 243). Once sustainability objectives are clearly prioritized, indicators are useful for measuring progress toward the desired state as a result of changes to management. There is a large body of literature devoted to the development, validation, and use of indicators designed to assist in policy implementation and for conducting research on the relative sustainability of different farming systems (Rigby et al., 2001; Zhen and Routray, 2003; Bell and Morse, 2008). Conclusions made are predicated on the assumption that the selected indicators accurately reflect how the system is performing, and hence the choice of indicators needs to be transparent. Each indicator needs to be validated to show that it is a reasonable proxy for the processes and functions it is meant to represent (Bockstaller and Girardin, 2003). Because sustainability involves multiple goals and objectives, it is also important to use a mix of environmental, agronomic, economic, and social well-being indicators when evaluating the sustainability of whole system performance (Zhen and Routray, 2003; Van Cauwenbergh et al., 2007). The use of multiple indicators also enables the identification of tradeoffs and synergies. At present, the bulk of the work on sustainability indicators for agricultural systems has focused on the first three goals (to satisfy human food and fiber needs, to enhance environmental quality and the resource base, and to sustain the economic viability of agriculture), with social indicators for the fourth goal (to enhance the quality of life for farmers and society as a whole) less developed and researched. Characteristics and Types of Indicators Indicators selected need to be appropriate to the sustainability objectives and need to have the following characteristics: Accurately reflective of the process or function it represents. Sufficiently sensitive to pick up changes over time and among different farming systems. Feasible to measure in terms of time, expense, and level of skill required. Understandable and relevant to end-users. In reality, finding ideal indicators is difficult and compromises have to be made. For example, an accurate representation of many system functions (such as nutrient cycling and retention) requires intensive data collection, monitoring from multiple locations, and
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Toward Sustainable Agricultural Systems in the 21st Century repetition at appropriate time intervals. Those tasks are expensive, time-consuming, and require specialized skills. Thus, a spectrum of indicators has emerged that range from simple, low-cost, means-based indicators to more costly outcome- or effect-based indicators. Means-based and outcome-based or effect-based indicators fall in different stages along the cause–effect chain of environmental impacts as a result of farming production practices (Figure 1-3). Means-based indicators are restricted to description and quantification of practices, whereas outcome-based (or effects-based, as in Figure 1-3) indicators can be assessed at a number of steps along the chain, from emissions (for example, what pollutants are released from the farming operation) to direct measurements of resulting environmental impacts. Measuring impacts directly seems to be ideal, but it can be difficult and expensive to accomplish, with considerable uncertainty in assigning cause-and-effect relationships. Furthermore, some effects might not be detectable for many years, by which time they might be difficult to reverse. Thus, having good indicators from earlier steps in the cause–effect chain is essential for taking timely preventive actions. (See Figure 1-4, Payraudeau and van der Werf  for more detailed discussion of indicator classification.) An example on nonpoint source pollution helps illustrate the difference between means-based and outcome-based indicators. Means-based indicators record what practices and technologies are being used and then rely on previous scientific models to infer the likely effects of using the practices. For example, it is common to equate the use of recommended BMPs (such as presence of buffer vegetation or use of nutrient budgets, slow release fertilizers, cover crops, or sufficiency tests) with a standardized coefficient to reflect FIGURE 1-3 Cause–effect chain from farmer production practices to environmental impacts for a farming region. NOTE: Pressure indicator is an indicator that provides information about anthropogenic stresses acting on an ecosystem. State indicator is an indicator that provides information about the state of an ecosystem or specific biota within ecosystems (Payraudeau and van der Werf, 2005). SOURCE: Payraudeau and van der Werf, 2005. Reprinted with permission from Elsevier.
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Toward Sustainable Agricultural Systems in the 21st Century expected reductions in nonpoint source pollution. On the other hand, outcome-based or effects-based indicators require some combination of direct measurement of reductions in runoff, leaching, levels of nutrients in surface and ground water, or outputs from simulation models. In some situations, only means-based indicators are feasible and accessible to end users, particularly for large-scale monitoring for policy and regulatory contexts. Nonetheless, caution is to be used when relying on means-based indicators, particularly if changes measured in such means-based indicators (for example, BMP use) have a more complex relationship to landscape-scale outcomes than was present in the experimental conditions used to estimate their original impact coefficients. The most robust means-based indicators are those with simple causal links derived from a substantial body of evidence compiled from real-world conditions. A good example is the use of percentage of ground cover as an indicator of soil erosion potential, a relationship that has been demonstrated many times across different soil types, slopes, and climates. There are dangers associated with the use of outcome-based indicators, notably when effects can be measured, but the causal links to what is actually responsible for causing the effects are not clear. That particular concern occurs when outcome-based indicators are used in a regulatory context or for awarding incentives. Using water quality as an example, changes in nutrient loadings in streams or lakes can be measured directly, but identifying the cause of the changes can be extremely difficult in the absence of detailed and comprehensive knowledge of surface or ground water hydrology, pollutant transport, and in-stream processing of pollutants in the region. Nutrient loadings in streams and lakes might reflect more of the effects of historical management than of the current one. An increase in nutrient levels in a section of a stream might not relate to the practices used on farms immediately adjacent to the stream, but rather to some combination of local input and loading from subsurface water that contain nutrients derived from a much larger area within the watershed. In that case, stream nutrient levels would not be a good indicator for forming the basis of farm-level regulatory decisions. Means-based and outcome-based indicators can also be developed for measuring the impacts of farming systems on economic and social sustainability goals. However, there is typically a small scientific knowledge base to allow an analyst to link the use of particular production practices or agricultural system with a prediction for economic or social outcomes. For example, whether adoption of a particular farming practice or system is likely to increase the economic well-being of farmers and their households might be estimated by a means-based indicator such as the degree of adoption of a particular practice. However, to link well-being to that practice might require linking adoption to such factors as reduced costs of production per unit output. An outcome-based indicator might be to examine levels of net farm or household income among farms using the practice. Regardless of the indicator selected, complexities in the relationship between use of the practice and accomplishment of the ultimate outcome of improved economic well-being (such as variation in the management abilities or approaches of individuals, interactions among different cropping or livestock production activities on a farm, or different marketing outlets) make interpretation of each type of indicator challenging. Relating Indicators to Sustainability Goals and System Attributes The usefulness of indicators can be improved if they are designed to reflect performance in terms of a more complete set of systems attributes, including measures of productivity, resource-use efficiency, and robustness. For example, a commonly used indicator for the objective of high productivity is crop yield, typically average yield per acre. However
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Toward Sustainable Agricultural Systems in the 21st Century a more complete indicator would also include assessment of system robustness (such as a measure of variability in yields over space and time, or the probability of yields falling below a certain threshold) and of resource-use efficiency of the system as measured by nutrient, fertility, water, and energy use expressed per unit crop yield. Similarly, measures of biodiversity could be improved by incorporating considerations of productivity (number of species supported and their population sizes), robustness (fluctuations in population sizes, and the number of extinctions and invasions over space and time), and system efficiency (for example, the amount of land and water used to support a given number of species and populations). In the case of social goals, such as increasing community social and economic wellbeing, it would be valuable not only to examine productivity in terms of the ability of an agricultural system to produce desired outcomes (for example, increased net farm income, improved availability of affordable quality food, and decreases in income inequality), but also to pay attention to the robustness (stability of outcomes in the face of changing biophysical, market, and policy circumstances). Interpreting Indicators Indicator values have to be interpreted to be meaningful: that is, significance needs to be assigned to an indicator ’s numerical (or qualitative) value. Threshold values have not been established for many environmental indicators. Conclusions are typically drawn on the basis of whether numerical values are higher or lower than before, and rarely in terms of whether the differences are likely to be functionally significant. For example, measures of soil organic matter are a cornerstone of most sustainability and soil quality assessments, being seen as an integrative indicator for soil properties such as moisture-holding capacity, physical structure, and nutrient supply capacity. However, the numerical level that would be considered good, or what change in soil organic matter levels constitutes a significant functional change, has not been established (Loveland and Webb, 2003). In contrast, nutrient concentration thresholds for ecological integrity have been established for some freshwater lakes (Carpenter and Lathrop, 2008), but no such thresholds for ecological integrity currently exist for nitrate or phosphorus concentrations in freshwater streams. Clearly, improving the understanding of the relationships between sustainability indicators and their functional significance is a priority for future work. Integrating Diverse Indicators in Holistic Assessments Using even well-designed indicators still begs the question of how to make a holistic assessment of the relative sustainability of different systems given the multiple indicators that represent various sustainability goals and objectives. Even a single sustainability goal, such as enhancing environmental quality, contains many subobjectives, such as water quality, air quality, water use, and biodiversity conservation, each of which may be measured by multiple indicators. One practice is to combine individual indicators into an index, based on some additive (often weighted) procedure. A single index, however, obscures the values inherent in its calculation—which attributes are weighted more than others—and can be particularly problematic if the direction of change is positive for some measures but negative for others (Suter, 1993; Fisher et al., 2001). Despite that issue, reducing multiple indicators into a single indicator is done in some policy contexts, such as the use of an environmental benefits index to implement the Conservation Reserve Program of the Farm Bill.
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Toward Sustainable Agricultural Systems in the 21st Century An alternative is to evaluate system performance without creating a single number, in which case any tradeoffs or synergies might be identified. For example, the same suite of indicators is monitored over time across all countries and regions in EU, making it possible to look at the spatial distribution of relative importance of different sustainability issues and where trends are positive or negative (European Environment Agency, 2006). Data show that soil erosion and water overdrafts are most serious in the Mediterranean countries, whereas nitrate pollution is greatest in northern Europe. However, positive nitrogen balances are declining in most countries where the problems are most severe (for example, the Netherlands) and have decreased by 16 percent across the EU as a whole between 1990 and 2000. Other indicators used include greenhouse-gas emissions, changes in biodiversity, and landscape patterns. (See European Environment Agency  for the complete list.) Those findings are then integrated into the various policy directives and used to evaluate program effectiveness. Programs on indicators have been developed by other institutions, including the FAO (Tschirley, 1997), United Nations (United Nations, 2007), World Bank (Dumanski et al., 1998), USDA (USDA-ERS, 2003), various university programs in the United States (Aistars, 1999), and such nonprofit organizations as the International Institute of Sustainable Development (Pintér et al., 2005) and the Land Stewardship Project (Keeney and Boody, 2005). Although the proliferation of programs to develop indicators reflects the growing interest in quantification and evaluation of the sustainability of agriculture, there is not an alignment or consensus among the different organizations and scientists involved about the most appropriate or useful set of indicators. In other words, there are different interpretations, methods, and approaches for developing and using indicators. Collaborative efforts among different organizations to develop agreement about key indicators needed for measuring sustainability—and particularly performance outcomes—have emerged in the U.S. agriculture sector, such as Field to Market: The Keystone Alliance for Sustainable Agriculture (Keystone Center, 2009) and the Stewardship Index Initiative for Specialty Crops (Stewardship Index for Specialty Crops, 2009). Some university programs in the United States have also convened and attempted to collaborate in the development of indicators (for example, the Sustainable Agriculture Research and Education Program at University of California). It should be noted, however, that the conclusions reached by the different methods can vary substantially even when applied to the same system (for example, van der Werf et al., 2007). Those differences emphasize the need for careful assessment of the assumptions behind each method and for more method comparison studies to be done. SUMMARY Sustainable agriculture can involve a diverse number of possible farming practices or farming systems. The committee’s definition of sustainable farming does not accept a sharp dichotomy between conventional and sustainable farming systems, not only because farming enterprises reflect many combinations of farming practices, organization forms, and management strategies, but also because all types of systems can potentially contribute to achieving various sustainability goals and objectives. Sustainability is a process that moves farming systems along a trajectory toward meeting societal defined goals, as opposed to any particular end state. As such, management systems will inevitably need to be adjusted to meet sustainability goals and objectives when circumstances and societal desires change. Sustainability of agriculture is a complex and dynamic concept. The committee rec-
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Toward Sustainable Agricultural Systems in the 21st Century ognizes that the concept is inherently subjective in that the goals will be viewed in different ways by various groups in society. Further, even with broad agreement for certain goals, the relative importance assigned to one goal over another will be highly contested. The definition of societal goals for sustainable agriculture emerges from the domain of politics, not science. Yet, science plays essential roles by generating knowledge to inform the political process, making predictions about outcomes likely to result from different management systems, answering specific questions when needed, and expanding the range of alternatives considered. Science also can supply the knowledge needed to develop new agricultural technologies. Finding ways to measure progress along a sustainability trajectory is an important part of an experimentation and adaptive management process. The rationale for selecting the indicators used to measure progress needs to be explicitly stated and justified since the choice is a political rather than a scientific question. It is important that indicators used are shown to be appropriate surrogates for the sustainability outcomes they are meant to represent, especially in the case of means-based indicators. Social indicators, in addition to environmental and economic measures, will help provide a more comprehensive assessment of movement toward sustainability goals; however, much more research is needed to develop appropriate social indicators because the development of such measures to date has been fledgling. ORGANIZATION OF THE REPORT Using the terms and the boundaries defined in this chapter, this report provides an overview of how U.S. agriculture has evolved over the years to the current state, and farmers’ successes and the challenges they face (Chapter 2). The state of knowledge on farming practices and management systems that can increase the environmental and production (Chapter 3), social, and economic (Chapter 4) sustainability of agriculture are then discussed. However, individual farming practices are components of an agricultural system. Knowledge and understanding of the sum of the parts are important in designing, fine-tuning, and adapting the system to improve sustainability. Chapter 5 uses a few systems to illustrate how a collection of farming practices works in concert to improve sustainability and to illustrate some potential tradeoffs. In spite of the positive attributes of some farming practices and systems that can improve sustainability, they are not necessarily widely adopted by farmers. Chapter 6 highlights the importance of markets, policies, and research in shaping trajectories of farm change, and examines influences on farmers that make some of them more likely and able than others to change production practices or convert to new farming systems. The approaches that could improve environmental, social, and economic sustainability, their practical applications, and their ability to meet those goals are best illustrated in examples of real-life farms in Chapter 7. The committee used seven farms featured in the report Alternative Agriculture (NRC, 1989b) and nine additional farms as case studies to illustrate points made earlier in the report. Conclusions drawn in earlier chapters were used as the basis of the discussion on the lessons learned in U.S. agriculture that are relevant to agriculture in other regions in Chapter 8. A representative of the Gates Foundation specified that the foundation was most interested in the relevance of lessons learned to sub-Saharan Africa, which is the focus of Chapter 8. The committee’s findings and recommendations for how to advance a systems approach to farming and to strengthen federal policies and programs related to improving agricultural production in the United States are summarized in Chapter 9.
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