There may well come a time in the future when parents who choose to have children become stigmatised. Imagine the scene at an "Islington" dinner party some years from now when someone around the table mentions that their partner is pregnant. Cutlery is dropped onto plates heaving under the weight of the locally grown organic vegetables and the person is admonished for being "selfish beyond comprehension". How dare they not think of the global impact of that child. Some though are already thinking along these lines and are sterilising themselves against the possibility of lumping the world with what could be a climate tipping pile of carbon emissions, otherwise known as a child.
The right over one’s womb is of course beyond question, and I do not, in any way, suggest that it should be taken from them. It is the fact that the rest of the rational population will ultimately need protecting against possible demands for legislation to be passed. We are probably not far from a world where we have to undertake "carbon awareness training" if we wish to reproduce and how to offset the carbon of the child we bring into the world. Currently many of us would laugh at such a suggestion, but I suspect if you raised that idea in environmentalist circles they would all think it brilliant and seek to implement it.
Caring for the planet through this course of action (self-sterlisation) raises a valid question though: How to reduce the carbon footprint further so as to alleviate the level of one’s guilt to zero? There is a course of action that I could suggest that these people take, but I don’t think they’d like the consequences.