Whatever The Big One is. Here in the San Francisco Bay Area, the big one is a devastating earthquake; in the Gulf region, the big one is a devastating hurricane or two -- you get the picture.

http://www.treehugger.com/files/2008/11/on_moving_towar_1.php

This article is on getting enough protein in a vegetarian diet. I figure here in the Bay Area all the dogs and cats will be eaten fairly quickly, and the wild animal population is less than the human one, so the diets will trend toward vegetarian as time goes by and we're waiting for rescue.

Veggies are more nearly storable than meat and more easily grown if the disaster continues for more than a season (the Really Really Big One).