It's pretty silly to couple an apocalypse and shopping. I would rather name over consumption as an attributing factor to an apocalypse of the "world as we know it." With time being as seeming slow as it is and given the technology of our culture in it's current state, we are afforded an opportunity to prepare for whatever we expect may be down the road by studying, and yes even buying things that might be useful to us as we learn to live differently. On that note I found a used copy of this remarkable book titled American Indian Food and Lore by Carolyn Neithammer for a buck ninety eight on Amazon. This book is specific to the southwest. It's a botanical and cook book all in one. I was surprised to learn that here in NM the Apache's barely stayed in one place due to the shortage of edible vegetation in season at a given time. According to the book older tribes that lived for hundreds of years on the same land had a larger cooking palate of vegetation while younger tribes ate more meat than vegetables. Logically a tribes menu reflects the depth of their plant knowledge. I would recommend finding a book of this sort for your own geography. I'm going to take mine out and see if I can harvest and eat a meal made just from what's growing wild in my area, a skill that may just come in handy.