Environment & Energy

Between the effects of climate change, resource depletion, and food shortages, that's when I think it will start to unravel. Small wars turning into big ones as water and farmland become vital for survival, social order breaking down, poverty skyrocketing, oligarchs claiming more of the remaining wealth for themselves, and global trade becoming more and more expensive. Eventually global civilization will fracture and move towards regional nation-states, and large portions of the planet will be mostly uninhabitable as wet bulb temps and crop failures turn the tropics into hot, steamy hellscapes. Climate refugees will move largely north, but may be welcomed as falling birthrates make immigrants a hot commodity.