Photo: Alex LeungCross-posted from the Natural Resources Defense Council. Walmart plans to expand into urban markets with smaller stores that carry fresh food, writes Jayne O'Donnell in USA Today. O'Donnell reports that the giant retailer is looking for suitable locations in city environments across the country. Is this a good thing?  Urbanists, preservationists, and smart growth advocates, including yours truly, have roundly criticized Walmart's well-known business model of building mega-stores of up to 200,000 square feet with 15 to 20-acre surface parking lots on the outer suburban fringe. Notwithstanding the company's efforts to be known for sustainability, no corporation has been more emblematic of the …