On one hand many countries will invest in heavy industry, manufacturing, and fall back to fossil fuels.
On the other hand, economy overall should slow down and consumption of non-essential goods and services will drop.
I’m not expecting any definite answers or numbers, of course, just some food for thought.
Depends on how many humans die.
The tools that would kill enough humans to matter would hurt the biosphere much worse than it hurts humans. Otters and bees don’t have gas masks and nuclear shelters.
Think Covid but with purpose.
Yes, but the opposite way you might be thinking since mass death from war and other catastrophe is strongly correlated with very high birth rates. We’re on track for the global population to stabilize around 10 billion right now, but if billions die in a world war we will probably go exponential again for a long time.
This is the best and simplest answer.