It’s a step. While our personal actions matter, unless I am in control of a major pollution source (energy, transportation, agriculture, ?) does it make more sense to put effort into changing the rules for everyone?
[1] You can just google it.
One/two/three less people will have negligible impact but if the most environmentally aware people are the ones not having children, not passing on their values, the next generation will be missing their voices. Fixing this is a relay race through the generations, not a sprint for an individual or couple.
If anything, the most environmentally aware of us should have more kids than average to help dilute the ranks of ignorant people and boost overall awareness. That would lead to higher chances of good leadership in 2060 and beyond.