Without getting deep into both the research data and dumb researchers that truly don't know what they're doing, I mentioned the crops for a reason. Human societies operate on board, energy-responsive effects. The desire (since it's always economists involved) is to put it in purely economic terms, but that isn't actually what's going on. It's just economic activity is highly intertwined with available energy supplies. There's also a direct function of space and space constraints that shows up all the time. Culture & Society does matter a chunk, but even the Amish are responsive to the effects. (But that's TFR from 7 down to 5.5 in a bad economy, haha)
The effect is also mostly "baked in" to a generation set. That crops up in a lot of other places, but the energy supply, food supply and general outlook from about Age 5 to Age 15 will have permanent effects on that age cohort. This is why the Japanese TFR fell off a cliff in 1970 or so. The Post-War generation lived in a time of rapid expansion, but their children did not as the space rapidly vanished. Even as the economy was still flying for the next 20 years.
The Imported Calorie stuff also always matters for Geopolitics and Economics. If you're having to send out resources to get food, your country either has to go conquer a food producing area or you're population will shrink until it reaches an equilibrium because you have to be a Net Energy exporter. This is why the whole "Chinese Century" stuff was doomed. Actually same with Japan hitting a massive wall and stagnating for so long.
Sad part is this is the type of information that's actually pretty well understood, but you'd actually have to be very careful to talk about it publicly. It upsets too many apple carts and, well, it gives away the game that environmentalists are.... fill in the blank.