Some analysts, ranging from scientists David Pimentel of Cornell University to financial advisor and philanthropist Jeremy Grantham, dare to underline the possibility of a darker alternative future. Defying the optimistic majority, they suggest that humanity long ago overshot a truly sustainable world population, implying that apocalyptic horsemen old and new could cause widespread death as the environment unravels. Most writers on environment and population are loathe to touch such predictions. But we should be asking, at least, whether such possibilities are real enough to temper the usual demographic confidence about future population projections.Revisiting Population Growth:
The Impact of Ecological Limits
Let's see, water shortages, food shortages, war... all predicted with peak everything and climate change even if you are conservative.
It's too complicated to model, so we'll just run this experiment in the lab called Earth.