As an example of this, a healthy female rabbit will produce anywhere from 20 to 50 additional rabbits in a single year. There have been many documented explosions of rabbit populations due to lack of natural predators which have caused significant ecological crisis.
They've evolved to reproduce so quickly because they are the "food" in the food chain. Without the predators above them, they will _eventually_ stop reproducing so quickly because they are only killing themselves by doing so.
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.
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.
However, species don’t evolve as a unit. Which genomes are most likely to survive a die-off?
All else being equal?
The ones with the most copies. So not the ones that are holding back on reproductions.
(Perhaps if we had to contend with some homo-vampirus, we wouldn't have global climate change...)
It looks more and more like we're headed toward a world where we'll regenerate extinct species in labs; and grow our steaks in meat factories. If we no longer need cattle farms, it's possible we'll vote to preserve more lands.
- the existence species regeneration does not imply the incentivize to regenerate and manage the vast majority of extinct species
- lack of gene samples for vast majority of species
- we don’t and are not very close to having a viable model for environment and species fitness so we can’t accurately model what specifies to regenerate
- new species populations have to be managed before and after initial release
- land and labor capital investmentIt has been extremely difficult to reintroduce functionally extinct species (ie, regenrate populations in zoos, and then reintroduce them to their original habitat). The animal culture piece is really big.
But probably the biggest issue is that, in almost all cases, the problems that led to extinction in the first place - lack of habitat, poaching, etc - rarely get better with time.
I think a more realistic point of view is that once a species is gone, it's truly gone, and that we should worry about keeping alive those still existing, because there's no "undo" button.
early life experience learning from parents/siblings are essential for knowing how to properly behave in their environment.
Which ecosystem are these species going to inhabit? How can we keep them alive when other currently existing species are at risk or going extinct?
https://www.rifters.com/blindsight/vampires.htm
The book is great “what if?” in several directions at once including human vampires.
Perhaps without an apex predator the prey species would evolve out of the overpopulation problem eventually. However, species that evolve with a predator tend to reproduce more quickly, which helps avoid being completely wiped out by the predator - when the population constraint impose by the predator is removed, the prey population explodes, leading to particularly pronounced problems.
(Perhaps if we had to contend with some homo-vampirus, we wouldn't have global climate change...)
Overall, humans already interfered in the shape of the ecosystem by removing wolves. You're correct that there's no objective 'correct' state for an ecosystem. But it is worthwhile to help balance ecosystems, especially when they have been unbalanced by our own interventions. Without restoration work, we're headed to a world with humans, livestock, and the few species that manage to live on our margins.