Dynamic interactions between and within the biogeophysical and human environments lead to the production, processing, distribution, preparation and consumption of food, resulting in food systems that underpin food security. Food systems encompass food availability (production, distribution and exchange), food access (affordability, allocation and preference) and food utilization (nutritional and societal values and safety), so that food security is, therefore, diminished when food systems are stressed. Such stresses may be induced by a range of factors in addition to climate change and/or other agents of environmental change (e.g. conflict, HIV/AIDS) and may be particularly severe when these factors act in combination. Urbanization and globalization are causing rapid changes to food systems. Climate change may affect food systems in several ways ranging from direct effects on crop production (e.g. changes in rainfall leading to drought or flooding, or warmer or cooler temperatures leading to changes in the length of growing season), to changes in markets, food prices and supply chain infrastructure. The relative importance of climate change for food security differs between regions. For example, in southern Africa, climate is among the most frequently cited drivers of food insecurity because it acts both as an underlying, ongoing issue and as a short-lived shock. The low ability to cope with shocks and to mitigate long-term stresses means that coping strategies that might be available in other regions are unavailable or inappropriate. In other regions, though, such as parts of the Indo-Gangetic Plain of India, other drivers, such as labour issues and the availability and quality of ground water for irrigation, rank higher than the direct effects of climate change as factors influencing food security. Because of the multiple socio-economic and bio-physical factors affecting food systems and hence food security, the capacity to adapt food systems to reduce their vulnerability to climate change is not uniform. Improved systems of food production, food distribution and economic access may all contribute to food systems adapted to cope with climate change, but in adopting such changes it will be important to ensure that they contribute to sustainability. Agriculture is a major contributor of the greenhouse gases methane (CH4) and nitrous oxide (N2O), so that regionally derived policies promoting adapted food systems need to mitigate further climate change.

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/ Environmental degradation, competition for resources, increasing food demands, and the integration of agriculture into the international economy threaten the sustainability of many food production systems. Despite these concerns, the concept of sustainable food production systems remains unclear, and recent attempts to appraise sustainability have been hampered by conceptual inconsistencies and the absence of workable definitions. Six perspectives are shown to underpin the concept. Environmental accounting identifies biophysical limits for agriculture. Sustained yield refers to output levels that can be maintained continuously. Carrying capacity defines maximum population levels that can be supported in perpetuity. Production unit viability refers to the capacity of primary producers to remain in agriculture. Product supply and security focuses on the adequacy of food supplies. Equity is concerned with the spatial and temporal distribution of products derived from resource use. Many studies into sustainable agriculture cover more than one of these perspectives, indicating the concept is complex and embraces issues relating to the biophysical, social, and economic environments. Clarification of the concept would facilitate the development of frameworks and analytical systems for appraising the sustainability of food production systems.

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Recently it has been recognized that changes in the chemical composition of the atmosphere are likely to alter the earth's climate, and that these alterations may have severe implications for agriculture and other economic activities. This has stimulated research into the possible consequences of altered climatic regimes on several attributes or components of agri‐food systems. Current consensus suggests that a global climatic warming, induced by increased concentrations of CO2 and other “greenhouse” gases, is likely, and hence the possible implications of warmer climates for agriculture has received considerable attention. Several analytical procedures have been employed in these studies and it is timely to assess the characteristics and achievements of these independent efforts. This paper classifies and reviews studies that examine the implications of climatic warming for agriculture. Three approaches to assessment are recognized. Crop yield analysis identifies the effects of a specified change in climate on productivity levels for individual crops in particular locations. Spatial analysis examines the implications of climatic warming for the area and location of lands suitable for crop production. Agricultural systems analysis focuses on the relationships among components of agri‐food systems. Much remains to be learned about the effects of climatic warming on agriculture. The use of existing information to develop a comprehensive analysis is hampered by differences in analytical approaches and in climatic change scenarios, and by the virtual absence of information on the possible implications of climatic change on agriculture in developing nations. Nevertheless, current evidence suggests that a warmer climate could create a more favorable environment for wheat (Triticum aestivum L.) and grain corn (Zea mays L.) in Canada, Northern Europe, and the USSR, and restrict opportunities in the USA.