Save Money, Live Better, Save the Planet?

There is growing concern  about the environmental costs of and threats to the sustainability of our food systems.  You can see this increased awareness reflected in the efforts of large retailers such as Walmart.  This story http://www.sfgate.com/science/article/Walmart-s-organic-push-could-alter-California-5396629.php describes Walmart's drive to increase the number of organic options they provide.  Other retailers such as the supermarket conglomerate, Tesco have pushed their suppliers to provide various sustainability metrics that they share with consumers.  As the story points out, any changes that such large food sellers enact can have large impacts on the entire food system.  It also brings up some interesting questions about what a "sustainable food system" looks like.