This is the latest installment of Harvest Public Media’s Field Notes , in which we talk about important issues related to food production. Retailers and restaurants like Whole Foods, Chipotle, Safeway, McDonald's and Wal-Mart are all providing information to consumers about how sustainably some of their foods were produced. But as I found doing this story, it's hard to know just what "sustainability" means and how to judge whether food was produced in a "sustainable" way.