I’ve been looking for suggestions of individual actions one can take to reduce CO2 emissions. In particular, ones which actually make a big difference (unlike, e.g., switching to LED lightbulbs). Everywhere I look, all I see is "have one fewer child" dwarfing all other actions by effectiveness. It's all anyone talks about.
The Web is full of figures like this one. It shows the one-fewer-child recommendation being equivalent to about 60 t/y, where the next-best options like “sell your cars”, “stop flying” or "be vegan" are mostly in the 1–2 t/y range. So high, they had to clip and compress the range on the graph so you could even see anything else. That looks pretty stark. That figure is so high, it seems as if nobody could ever hope live sustainably if they had even one child. They might as well be taking a long-haul flight every 10 days for the rest of their life! Now, we definitely shouldn't discount conclusions just because they are surprising or uncomfortable, but we should scrutinise them. That feeling of "…really?" is the first hint something might not be right.