A generally accepted definition of food security is "a situation in which all people at all times have access to adequate quantities of safe and nutritious food to lead a healthy and active life". This definition requires three basic conditions to be met: 1) adequacy, i.e. supplies from domestic production, stocks and imports are sufficient to meet the nation's needs, 2) availability i.e. stability of supply both spatially and temporally throughout the year and 3) access, i.e. the population has sufficient purchasing power to gain access to its food needs. Strategic grain reserves help address the stability problem.
In most countries there groups of people who are, or are vulnerable to, food insecurity. These are usually separated into two groups, those who are chronically food insecure and those who are transitory food insecure. The chronically food insecure include those sectors of the population which lack adequate income, assets and/or resources at the household level to produce or otherwise gain access to the basic food needs of the household. Chronic food insecurity results from structural problems and as such cannot be overcome by periodic interventions of food from the reserve. Its resolution requires programmes aimed at identifying and conquering the underlying reasons for the population's inability to produce sufficient foodcrops, or other economically tradable outputs, e.g. non-food crops, to meet their needs. In the meantime they require continuing targeted support programmes aimed at providing the means for them to gain access to their basic food needs. Meeting the supplementary food needs of such population groups would not normally be considered to be a function of a strategic grain reserve, but rather for specialised relief programmes; such as food for work, food stamps or other targeted interventions. The transitory food insecure are those households which, under normal circumstances, are able to produce or gain access to their basic food needs but are vulnerable to supply problems when external shocks affect their food production systems or distribution chains for a limited period of time. For rural populations this is generally related to instances which have a seasonal impact on crop production, e.g. drought and floods, while for urban populations it is related to the availability of, and the ability to access through purchase, food in the marketing chain. By their nature events resulting in transitory food insecurity are usually of limited duration, e.g. a single crop season, and, once conditions return to normal, the affected population is usually able to rapidly recover its food security. Due to the unpredictability and non-continuing nature of such events, a strategic grain reserve provides a useful tool for helping to cope with the problems of transitory food insecurity when it arises.
By providing a breathing space between the identification of the possibility of either a national or a localised food shortage occurring and making the necessary arrangements for mitigating its impact, a food security reserve provides a first line of defence for coping with food emergencies. For the purposes of a food security reserve a food emergency can be defined as: "when there are clear indications that an acute and widespread food shortage, extensive suffering and dislocation in the life of the community on an exceptional scale are imminent, and that these dangers cannot be overcome by the normal supply procedures". Such an emergency would normally be caused by drought, floods, storms, earthquakes, crop failures resulting from pests or disease as well as from man-made causes, such as war and civil strife.
