fied cropping systems that reduce reliance on purchased inputs) is desirable because the dominant system types might limit the range of technical or managerial possibilities in the pursuit of greater sustainability.
A systems approach to agricultural research is necessary to identify and understand the significance of the linkages between farming components so that a robust system that takes advantage of synergies and balanced tradeoffs can be designed. The report Alternative Agriculture published in 1989 by the National Research Council emphasized the importance of a systems approach to agricultural research. The growth of several systems-oriented approaches to farming, such as organic, biodynamic, and integrated crop–livestock farms, illustrates how farmers, industry, and academic communities can contribute to developing farming systems for improving sustainability. The committee provides two examples of how a systems approach is needed to inform design of farming systems that address two imminent challenges to the sustainability of U.S. agriculture.
Challenge 1: Producing cellulosic feedstock for biofuels. Scientific development of cellulose-producing crops and of the enzymes and production technologies needed to convert a range of feedstock to ethanol has been increasing. Federally set production targets for moving toward cellulose-based liquid fuels are in place. Early field-crop research indicates that perennial crops for cellulose production could contribute to reducing some of the negative environmental impact of agriculture on farmland and on aquatic systems through their proper placement in the landscape. Theoretically, different farming systems can be used to produce cellulosic feedstock. If economic efficiency is an important goal, widespread large-scale production of cellulosic crop monocultures will likely dominate. Monocultures are likely to be easier to manage and to process with regard to harvesting and conversion to fuels, and therefore might reduce production costs. Monocultures, however, could generate unwanted environmental or social side effects. Efforts to consider each of the four sustainability goals in the development of cellulosic feedstock farming systems will require attention to the costs and benefits of promoting greater enterprise and crop diversity both within farms and across landscapes. A holistic systems approach to research and development could identify opportunities for synergies and efficiencies that traditional disciplinary or production-focused research might miss.
Challenge 2: Social acceptability of concentrated animal feeding operations. Most commercial livestock production systems in the United States have evolved toward large-scale confinement production units that concentrate many animals in a small area. Some of those operations are geographically removed from the cropping systems upon which they depend for feed and waste recycling. Systems other than concentrated confined animal systems are evolving for dairy cattle, beef cattle, and hogs, and to a small extent for poultry, mostly targeted to niche markets. Public concerns about nuisances, environmental pollution, and animal welfare associated with certain types of large animal confinement operations (for example, poorly managed concentrated animal feeding operations that reduce aesthetics of communities or animal operations that use large quantities of subtherapeutic antibiotics) have intensified. Those concerns are reflected in social movements and marketplace preferences. Few scientific studies compare alternative, integrated systems