I see two failure modes for agriculture:
Unsuitable land. A tundra or desert would be an extreme example. Something like a steppe could lack arable land and almost require a nomadic lifestyle.
Land of plenty. If food is easy to come by and hunger almost non-existent, agriculture might not be worth the effort in the short-term.
in mode 1: those who can conserve food resources and potentially grow food where it would be naturally scarce will survive.
in mode 2: the population should expand to meet the available food and force scarcity eventually.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.