In some urban neighborhoods, buying food staples requires a lengthy journey to another (more white) part of the city. "food deserts" are significant problem for people whose resources are limites. based on the text, a food desert is a possible marker of

In this particular context, food desert is a possible marker of segregation
Food desert refers to the part of the nation that had  large quantity supply of healthy foods (fresh fruits, vegetables, good grains)
Segregation came to factor in the formation of these area because almost all the region that considered food deserta are the 'white upper middle class' area during the segregation period.

Accumulating more land so that your country can continue expanding without running into problems such as overpopulation