"Food desert" is a term developed in the context of governmental policy to refer to a geographical area in which poor people have limited access to fresh, healthy food. In the US, the USDA uses census tracts as the basic geographical unit, since it provides the population statistics and social data required for administration of government programs to alleviate dietary distress in "food deserts". The basic USDA publication reference is "Access to Affordable and Nutritious Food—Measuring and Understanding Food Deserts and Their Consequences: Report to Congress".
How did so-called food deserts arise? They arose from the conjunction of two broad causes in post-World War II US (and Britain, where the term originated in the early 1990s). The first cause is government agricultural policies that have caused rural depopulation. The second cause is government urban renewal policies that have concentrated poor and/or poor-minority populations in ghettos.
In the era, 1940s to 1970s, in the US, the federal government deliberately reorganized American agriculture to end small farming, which was seen as inefficient, and industrialize agriculture into large commodity farms. At the same time, federal subsidy was shifted toward commodity crops and refined products that cheapened processed foods (e.g. corn - and through corn fatty confinement beef-, wheat, dairy) that are now the target of governmental concern in food deserts. The decline of the number of farms and farm families reduced the economic viability of farm market downs, which declined in population and services. In turn, the decline of rural towns reduced the local markets for the produce of the remaining small local farmers, further reducing small farm economic viability. A vicious cycle became the death spiral of rural America.
At the same time, governmental policies concentrated, especially, poor, minority populations into urban districts often stripped and cleared of historical residential neighborhoods lacking food services. Low levels of consumer income, high urban ground rents, and other factors, such as union opposition to large value retailers, like Wal-Mart, prevented supermarkets from locating in these districts. To mitigate this situation, through the Food Stamp Act of 1962, food stamps were distributed to subsidize food budgets of these people, enabling them to purchase the now-recognized unhealthy processed foods. Additionally, federal subsidy of school lunch programs pushed unhealthy and nutritionally inadequate surplus industrially processed foods into schools, while simultaneously prohibiting schools from purchasing local fresh foods from the few remaining nearby small farms. This USDA policy (only changed, under public pressure, in the past two years) further deprived small farms of a possible market for their products.
Governmental policy often works to create new governmental programs to remedy the inadequacies and undesirable consequences of old governmental programs.
In Riverside County, federal and private charitable efforts are planned to alleviate the problems of food deserts in this Southern California region. A local newspaper exposes how this deleterious philosophy of government program expansion works. "Banning Councilwoman Debbie Franklin said ... the lack of access to groceries is a serious problem. Stores that used to operate on the east side of the city disappeared years ago, she said, and residents must travel across town, often by bus, to buy groceries" (Riverside [California], "Seeking to boost fresh-food access", The Press-Enterprise, Friday, May 25, 2002, D3). Let us note, bus service, including special buses, for point-to-point travel for the elderly and disabled, is a federally subsidized program. Why is it a problem that residents must use these buses to travel to a grocery store to buy food with their federally subsidized food stamps? It isn't, really; but it has to be so defined as inadequate, so that other federal programs, such as those to alleviate "food deserts", can have a rationale.
--- [Illustration of Fresh Food Deserts of Inland Southern California]
--- "Mapping Food Deserts in the US", Amber Waves, USDA, ERS (December 2011):
"Low-income: a poverty rate of 20 percent or greater, or a median family income at or below 80 percent of the statewide or metropolitan area median family income;
"Low-access: at least 500 persons and/or at least 33 percent of the population lives more than 1 mile from a supermarket or large grocery store (10 miles, in the case of rural census tracts)."
--- "Food Desert Locator", USDA, Economic Research Service.
--- "Access to Affordable and Nutritious Food—Measuring and Understanding Food Deserts and Their Consequences: Report to Congress", USDA Economic Research Service, Administrative Publication No. (AP-036) 160 pp., June 25, 2009.