If you have land it wouldn't hurt to have some survival crops. Something like sunchokes (a.k.a. jerusalem artichokes, bad name because they're not an artichoke and more like a sunflower) can grow well in a sectioned off space where they can't spread. In an emergency the tubers can be dug up and cooked, though they'll probably give you a lot of gas from the high inulin content.
Personally I love raspberries and black raspberries, which are easy to grow just don't plant them where they can spread and run wild. It's nice to have fresh berries!
I feel like you just avoided the subject. If everyone fully relies on someone elses agriculture for all their calories then that's putting all your eggs in one basket for an emergency. A farmer suddenly getting a thousand volunteers doesn't increase the number of potatoes ready for harvest.
Sunchokes are a suggestion because they are perennial, store in the ground, and require no care so long as they are contained.
Something like potatoes would be great for more people if they were perennial and hands off.