Comment by sdenton4
7 months ago
It's worth puzzling about the mechanisms that would lead a fast reproducing species to slow down...
My best guess is that internal competition for scarce resources leads to territoriality, which in turn might select for better resource utilization. Including reduced reproduction, which creates more resource competition. But this doesn't feel super obvious.
Otherwise, we have plague and starvation acting as stand ins for apex predators, which isn't much fun... And apparently isn't generally enough to reduce environmental externalities from over population.
The term of art for everything that includes those factors is "carrying capacity" [0].
It's not as much that the fertility necessarily drops, but that under some conditions the death rate equals or overtakes the birth rate.
And the system is dynamic. So conditions changes, as in some of your examples, even just because the population grows. EG scarcer resources.
[0] https://en.wikipedia.org/wiki/Carrying_capacity