This is a very Eurocentric discussion and book. I don't know about you, but living here on the West Coast of North America, when the cataclysm arrives, I'm going to run to the nearest Coast Salish person, preferably a wise elder. They have survived invasion, disease, the residential school experience and other calamities.
For most of their thousands of years here, they've developed appropriate technologies such as clam gardens, camas beds and fish weirs to sustainably harvest food. Additionally, the cedar and other trees and shrubs can provide clothing, implements and even transport.
That's why the T.S. Eliot quote at the top of Page 275 is so apropos.