cddt: We produce vast quantities of food today, but without continuity of the relevant inputs (fuel and machinery), the transition to pre-industrial farming would be extremely traumatic (and I do not mean psychologically). If fuel and spare parts were cut off tomorrow, we would not be able to continue to grow enough food for our population in the short to medium term. In the long term, yes it would be feasible, but how do you get to that point if you do not have sufficient food in the short term and also avoid a complete breakdown of society?
The government would be prioritising (and ordering manufacture of) fuel resources for essential services. Food production and food logistics is obviously one of those. There would be a large economic reorganization similar to a war economy.


