From hunting to farming
I will sketch out food-related scenarios, which are surprisingly standard in that they have caused successful and dominant nations, or societies, to reach a peak, and then head into decline. Invariably the underlying reason for their political collapse was not because they lost military power, but because they could no longer feed themselves adequately. Warfare and military losses were frequently the consequence, not the cause.
In more ancient historical periods, the food or water shortages were a mixture of poor agricultural techniques, adverse weather conditions, or both. Additionally, a typical drain on the agricultural resources for successful nations has been a rapid rise in the total population and development of ever-larger cities. The pattern of moving from living at the source of the food, in a small farm or hamlet, to being dependent on other producers and transport systems, automatically introduces a measure of vulnerability. Long-term survivors were generally nations that had managed to solve storage problems of food and water to carry them through lean periods. Nevertheless, prolonged droughts (or floods) were invariably the final blow.
A very localized and present example is apparent from the role of technology and transport, which both introduce serious potential weaknesses, for example, at the local neighbourhood level. In the UK, the supermarket food chains keep many types of food that need restocking every few days. This puts them at risk if there are snowstorms, fog, industrial actions, fuel shortages, or other events that interfere with the smooth flow of their supply chains. Electrical power loss can similarly result in many difficulties as it will destroy frozen and chilled goods, as well as making it difficult to operate the stores. I recently saw a local supermarket dumping the entire content of some freezers, as their equipment could not cope with a minor heat wave, so it is not just power losses that cause such wastage. Prolonged loss of transport and power causes chaos, and there are daily images of the consequences from news of war zones.
In a few paragraphs, I will offer a very simplistic perspective on how we moved from the hunter-gatherer phase into an agriculture-based one. There are many books and articles offering numerous examples and great detail, and for more in-depth discussion, one book I particularly liked was by Evan Fraser and Andrew Rimas, entitled Empires of Food.