Given the current state of AGW and Climate Change, taxing babies beyond replacement rate (2.1) is not a bad idea.
I mean it's political suicide, but I don't see anything morally wrong with it.
After all, we already subsidize babies with our taxing scheme. So you wouldn't even need to tax babies. You would just cut off the subsidy after 2 kids.
If we incentivize those who are childless and have shrunk their carbon foot print, that would also encourage people to make thoughtful decisions about baby making. Example: If someone didn’t have any children at all, then they should get tax free status or reduced premiums etc.
A woman increases her carbon foot print 10-20 times with every child. Medical costs and food and transport and pretty much everything is borne by the rest of us. Suspend benefits. Tax excess children and give tax breaks or retirement benefits to those who didn’t have children.
I suspect that retirement benefits would be a better incentive than tax free status. Most people hope that children would take care of them when they get older. It’s not worth the true cost of over population.