More people mean more mouths to feed. This is a problem for worldbuilders, who often forget to include sources of food for their large population centers. That town in the middle of that arctic wasteland, where exactly are they getting all those snacks from? That planet-wide megacity, are they all ordering out? While this particular problem may be one that can be ignored (audiences often don’t think of these matters or just assume it’s been solved but not presented to them) it may be worth considering as a worldbuilder. This problem is even more central in post-apocalyptic worlds, where food and other supplies (and particularly their absence) can play major roles.

This is an easy problem to solve. Simply add farms, hydroponic gardens, floating farms, kelp farms, farm terraces, nutrient vats, or other means to keep those mouths fed. In science fiction worlds, entire agricultural worlds and galactic trade routes may be a solution to this problem.