I can't help but wonder how large a "local area" would be required to supply all the food for NYC, Chicago, Los Angeles, or any other large metropolitan area. There's a reason why the midwest has lots of farm land despite having few people.

The problem with ideas like buy local produce is that they work fine for a few. But if you were to get a significant participation by the local population, you would quickly find severe shortages of local produce in many areas. Add to that the fact that many kinds of produce are not available locally and/or not available year round and you quickly realize why we devote significant energy to transporting food around.