Sustainable Agriculture

Agriculture has changed dramatically since the end of World War II. Food and fiber productivity has soared due to new technologies, mechanization, increased chemical use, specialization, and government policies that favored maximizing production and reducing food prices. These changes have allowed fewer farmers to produce more food and fiber at lower prices.

Although these developments have had many positive effects and reduced many risks in farming, they also have significant costs. Prominent among these are topsoil depletion, groundwater contamination, air pollution, greenhouse gas emissions, the decline of family farms, neglect of the living and working conditions of farm laborers, new threats to human health and safety due to the spread of new pathogens, economic concentration in food and agricultural industries, and disintegration of rural communities.

A growing movement has emerged during the past four decades to question the necessity of these high costs and to offer innovative alternatives. Today this movement for sustainable agriculture is garnering increasing support and acceptance within our food production systems. Sustainable agriculture integrates three main goals – environmental health, economic profitability, and social equity (Figure 1). A variety of philosophies, policies and practices have contributed to these goals, but a few common themes and principles weave through most definitions of sustainable agriculture.

Agricultural sustainability rests on the principle that we must meet the needs of the present without compromising the ability of future generations to meet their own needs. Therefore, long-term stewardship of both natural and human resources is of equal importance to short-term economic gain. Stewardship of human resources includes consideration of social responsibilities such as working and living conditions of laborers, the needs of rural communities, and consumer health and safety both in the present and the future. Stewardship of land and natural resources involves maintaining or enhancing the quality of these resources and using them in ways that allow them to be regenerated for the future. Stewardship considerations must also address concerns about animal welfare in farm enterprises that include livestock.

An agroecosystems and food systems perspective is essential to understanding sustainability. Agroecosystems are envisioned in the broadest sense, from individual fields to farms to ecozones. Food systems, which include agroecosystems plus distribution and food consumption components, similarly span from farmer to local community to global population. An emphasis on a systems perspective allows for a comprehensive view of our agricultural production and distribution enterprises, and how they affect human communities and the natural environment. Conversely, a systems approach also gives us the tools to assess the impact of human society and its institutions on farming and its environmental sustainability.

Studies of different types of natural and human systems have taught us that systems that survive over time usually do so because they are highly resilient, adaptive, and have high diversity. Resilience is critical because most agroecosystems face conditions (including climate, pest populations, political contexts, and others) that are often highly unpredictable and rarely stable in the long run. Adaptability is a key component of resilience, as it may not always be possible or desirable for an agroecosystem to regain the precise form and function it had before a disturbance, but it may be able to adjust itself and take a new form in the face of changing conditions. Diversity often aids in conferring adaptability, because the more variety that exists within a food system, whether in terms of types of crops or cultural knowledge, the more tools and avenues a system will have to adapt to change.

An agroecosystem and food system approach also implies multi-pronged efforts in research, education, and action. Not only researchers from various disciplines, but also farmers, laborers, retailers, consumers, policymakers and others who have a stake in our agricultural and food systems have crucial roles to play in moving toward greater agricultural sustainability.

Finally, sustainable agriculture is not a single, well-defined end goal. Scientific understanding about what constitutes sustainability in environmental, social, and economic terms is continuously evolving and is influenced by contemporary issues, perspectives, and values. For example, agriculture's ability to adapt to climate change was not considered a critical issue 20 years ago, but is now receiving increasing attention. In addition, the details of what constitutes a sustainable system may change from one set of conditions (e.g., soil types, climate, labor costs) to another, and from one cultural and ideological perspective to another, resulting in the very term "sustainable" being a contested term. Therefore, it is more useful and pertinent to think of agricultural systems as ranging along a continuum from unsustainable to very sustainable, rather than placed in a sustainable/unsustainable dichotomy.

When the production of food and fiber degrades the natural resource base, the ability of future generations to produce and flourish decreases. The decline of ancient civilizations in Mesopotamia, the Mediterranean region, Pre-Columbian southwest U.S. and Central America is believed to have been strongly influenced by natural resource degradation from non-sustainable farming and forestry practices. A sustainable agriculture approach seeks to utilize natural resources in such a way that they can regenerate their productive capacity, and also minimize harmful impacts on ecosystems beyond a field's edge. One way that farmers try to reach these goals is by considering how to capitalize on existing natural processes, or how to design their farming systems to incorporate crucial functions of natural ecosystems. By designing biologically-integrated agroecosystems that rely more on the internal cycling of nutrients and energy, it is often possible to maintain an economically viable production system with fewer potentially toxic interventions. For example, farmers aiming for a higher level of environmental sustainability might consider how they can reduce their use of toxic pesticides by bringing natural processes to bear on limiting pest populations. This might happen, for example, by planting hedgerows along field edges, or ground covers between rows, thereby providing habitat for insects and birds that prey on the pests, or by planting more diverse blends of crops that confuse or deflect pests (Figure 2). Maintaining a high degree of genetic diversity by conserving as many crop varieties and animal breeds as possible will also provide more genetic resources for breeding resistance to diseases and pests.

Conservation of resources critical for agricultural productivity also means taking care of soil so that it maintains its integrity as a complex and highly structured entity composed of mineral particles, organic matter, air, water, and living organisms. Farmers interested in long-term sustainability often prioritize caring for the soil, because they recognize that a healthy soil promotes healthy crops and livestock. Maintaining soil functioning often means a focus on maintaining or even increasing soil organic matter. Soil organic matter functions as a crucial source and sink for nutrients, as a substrate for microbial activity, and as a buffer against fluctuations in acidity, water content, contaminants, etc. Furthermore, the buildup of soil organic matter can help mitigate the increase of atmospheric CO₂ and therefore climate change. Another important function of soil organic matter is inducing a better soil structure, which leads to improved water penetration, less runoff, better drainage, and increased stability, thereby reducing wind and water erosion.

Due to a high reliance on chemical fertilizers, agroecosystem functioning has been disconnected from the internal cycling of key plant nutrients such as nitrogen and phosphorus. Phosphate minerals for fertilizer are currently mined, but global reserves are predicted to sustain food production for only another 50 to 100 years. Consequently, phosphate prices are anticipated to rise unless new reserves are discovered and innovations in recovery of phosphates from waste are developed. The recycling of nitrogen and phosphorus (at the farm and regional scale), improving efficiencies of fertilizer applications, and relying on organic nutrient sources (animal and green manures) are important elements of sustainable agriculture (Figure 3). Recycling of nutrients is facilitated by a diversified agriculture in which livestock and crop production are more spatially integrated. For these reasons, extensive mixed crop-livestock systems, particularly in developing countries, could significantly contribute to future agricultural sustainability and global food security.

In many parts of the world, water for agriculture is in short supply and/or its quality is deteriorating. Overdraft of surface waters results in disturbance of key riparian zones, while overdraft of groundwater supplies threatens future irrigation capacity. Salinization, nutrient overloads, and pesticide contamination are widespread water quality issues. Selection and breeding of more drought- and salt-tolerant crop species and hardier animal breeds, use of reduced-volume irrigation systems, and management of soils and crops to reduce water loss are all ways to use water more efficiently within sustainable agroecosystems.

Modern agriculture is heavily dependent on non-renewable energy sources, especially petroleum. The continued use of these non-renewable sources cannot be sustained indefinitely, yet to abruptly abandon our reliance on them would be economically catastrophic. In sustainable agriculture, the goal is to reduce the input of external energy and to substitute non-renewable energy sources with renewable sources (e.g., solar and wind power, biofuels from agricultural waste, or, where economically feasible, animal or human labor).

Agroecosystems cannot be sustainable in the long run without the knowledge, technical competence, and skilled labor needed to manage them effectively. Given the constantly changing and locality-specific nature of agriculture, sustainability requires a diverse and adaptive knowledge base, utilizing both formal, experimental science and farmers' own on-the-ground local knowledge. Social institutions that promote education of both farmers and scientists, encourage innovation, and promote farmer-researcher partnerships can increase agricultural productivity as well as long-term sustainability (Figure 4).



Questions of social equity often arise in discussions of sustainable agriculture. Wages for farm labor are so low in most industrialized countries that their agricultural sectors rely substantially on migratory labor from poorer nations, leaving farmers vulnerable to changing immigration policies and placing burdens on government social services. The questionable legal status of many of these workers also contributes to their generally low pay and standard of living, lack of job security, lack of opportunities for upward mobility, and exemptions from occupational safety protections considered standard in other industries. Pooling resources among many farmers to provide better housing, sharing labor among farms with different crops to even out the seasonality of work opportunities, shared equity in farm profits, mentoring workers to acquire and operate their own farms, and working on innovative ways to provide affordable health insurance and educational opportunities for employees are all alternative ways to increase labor equity and social justice.

Increasing consolidation of food manufacturers and marketers and of farm input suppliers means that farmers lack the economic power to negotiate better prices for their inputs and crops. This means their profit margins get squeezed, leaving many farmers with few resources to improve environmental and working conditions. Banding together in production, processing, or marketing cooperatives is one way that farmers can increase their relative economic power. Performing some processing functions on-farm before selling their crops, producing higher-value specialty crops, building direct marketing opportunities that bypass middlemen, and looking for niche markets are other ways that farmers can capture a larger share of the economic value of what they produce. Policies regulating consolidation can also protect farmers in the long-term.

Due to these economic pressures on farmers, many rural communities have become poorer as farms and associated local agricultural enterprises go out of business. Economic development policies and tax structures that encourage more diversified agricultural production on family farms can form a foundation for healthier rural economies. Within the limitations of the market structure, consumers can also play a role; through their purchases, they send strong messages to producers, retailers and others in the system about what they think is important, including environmental quality and social equity.

Finally, some of the same economic pressures that have hurt on-farm sustainability have also created social equity concerns for consumers in low-income communities, who are often left with little access to healthy food as conventional supermarkets move to more lucrative neighborhoods to bolster slim profit margins. Food production and marketing arrangements to bolster community food security, including community and home gardens, farmers markets, the use of fresh local farm produce in school meal programs, and local food cooperatives represent efforts to address these concerns (Figure 5). Moreover, a food systems approach also takes into account the impacts of farming practices on the safety and nutritional qualities of the final food products that reach consumers, for example by minimizing or eliminating toxic residues.

Social, economic, and environmental sustainability are closely intertwined and necessary components for a truly sustainable agriculture. For example, farmers faced with poverty are often forced to mine natural resources like soil fertility to make ends meet, even though environmental degradation may hurt their livelihoods in the long run. Only by creating policies that integrate social, environmental, and economic interests can societies promote more sustainable agricultural systems.