Food deserts are rural or urban areas where at least 20 percent of the population lives in poverty and 33 percent lives without easy access to a supermarket or large grocery store. As a part of Michelle Obama's Let's Move! campaign, the USDA released an interactive map of the nation's food deserts.

But a number of urban bloggers are calling "foul" on the USDA's mapping rationale.

Food Deserts: The USDA Definition

The current USDA study uses census tracts as its geographic units. It defines a food desert as "a low-income census tract where a substantial number or share of residents has low access to a supermarket or large grocery store:

• A "low-income community" is defined as having 1) a poverty rate of 20 percent or higher, OR 2) a median family income at or below 80 percent of the area's median family income.
• "To qualify as a 'low-access community,' at least 500 people and/or at least 33 percent of the census tract's population must reside more than one mile from a supermarket or large grocery store (for rural census tracts, the distance is more than 10 miles)."

In its study, the USDA follows the "industry-standardized definition" of a supermarket where "a retailer must have annual sales of at least $2 million and contain all the major food departments found in a traditional supermarket, including fresh meat and poultry, produce, dairy, dry and packaged foods, and frozen foods."

Small, Independent Grocers Overlooked

In January 2011, before the USDA's map was released to the public, blogger Jim Griffioen had already called foul on the "damaging falsehood" that Detroit has no grocery stores in a scathing piece published at The Urbanophile.

Griffioen argues that while it may be true that major chains like Kroger, Safeway, or Meijer do not have locations within the city limits, Detroit boasts a high density of locally-owned grocers that serve their communities' needs for healthy food. A solid number of these independent stores are supplied by Spartan Stores, providing some uniformity of products available.

Intentionally or not, Griffioen also draws attention to an implicit bias in the common perception of Detroit grocery stores: many of the Spartan affiliates are owned by Chaldeans (Iraqi Christians), and many other local stores are supermercados owned by Hispanic immigrants.

Angie Schmitt of DC.streetsblog.org says that the USDA's use of supermarkets as indicators of food accessibility excludes small grocers and specialty grocers, including ethnic markets, butchers, or greengrocers.

Schimtt also points out that disregarding corner markets overlooks the very logical, business-oriented reason that supermarkets tend not to crop up in low-density cities like Detroit and Cleveland: large chain supermarkets require a very large customer base to sustain them.

In low-density cities where many people do not have cars and therefore require their stores to be within walking distance, no supermarket could reach the customer base it needs in order to meet its costs. Instead, corner stores, with their lower overheads, meet that need.

Read More:

• Yes, there are Grocery Stores in Detroit (The Urbanophile)
• In Defense of the Corner Market. (dc.streetsblog.org)
• Food Desert Locator (USDA)
• Access to Affordable and Nutritious Food: Measuring and Understanding Food Deserts and Their Consequences (USDA)