Humans aren't the only species on Earth. Mass extinction is bad for everyone living on this planet, mostly the other animals who suffer our destruction. I wish we could just live in equilibrium without killing off every species that isn't worth farming.
Earth is currently experiencing a sixth mass extinction, according to scientists.
Probably a bit of both? It says that women are having their first child at the age of 33.6, the oldest in the OECD. The older you have a child the more difficulty you will have so they also put money into fertility clinics.
It's not necessarily a health issue on a mass scale but an economic issue driving people to delay having children until they feel they can handle the responsibility.