The highest bar in the chart says "have one fewer child". It actually exceeds any others by extremely large margin [0].
How is that even considered as the option? One child less means halving population after every generation. Eliminate the population and problem solved?
All of our economics relies on having new people. Pensioners, ie people who cannot produce anymore, are effectively upkept by the younger generations, in exchange for their savings.
We don’t know how to run economies without young people. Look at the demographic issues in Japan, and lesser extent now in China.
They appear to be suggesting exactly that, if you read the asterisk:
"Cumulative emissions from descendants, decreases substantially if national emissions decrease."
So doing all the other ones actually lowers that one.
And even then it only makes sense if no-one else has more kids to compensate, so it's a personal action that will cut your personal carbon, but like most things in this area not something that works unless we all do it (globally)
Why would we have to reduce the population below a number which is sustainable? Nobody is advocating that.
The actual number could be fine tuned through tax breaks. Give childless couples an X% tax break. Single child families a Y% tax break. 2 child families no tax break. 3 child families a tax penalty. 4 child families a larger penalty.
One child less means halving population after every generation.
Only if you assume the average is two children per couple and a replacement reproduction rate, which doesn't fit the reality I know. We have a huge population in the billions precisely because that's not what is going on.
If we drop to something below exponential growth rates, this is not a tragedy.
Massive population reduction (I don't think any serious person is suggesting elimination) would be the single most effective advancement we can make in reducing our environmental problems. It's definitely a tough sell for politicians, and environmentalists seem dismissive of it -- which makes me doubtful of their policy prescriptions. If population reduction isn't on the table of things to achieve, then the other arguments are lost on me. Nothing is sustainable when scaled up to an ever increasing population size.
One fewer doesn't mean 2 -> 1 necessarily, does it? There's no sustainable way to maintain a greater-than-replacement birth rate long term (excepting self-supporting space colonies or something).
[0] https://www.lunduniversity.lu.se/drimage/1120/630/4832/fourc...