I'm an environmentalist, so I like the idea of reducing consumption. It's almost an axiom of economics by now that eduction leads women to have less children, thus reducing a nation's consumption.
But at some point, all nations will be developed. China's citizens are now "getting their car", and soon there will be millions more from Africa "getting their car".
My parents' parents had cars. My parents grew up with cars being ubiquitous, and managed to cultivate environmentalism despite owning cars. But for me, who learned the passion for environmentalism in no small part because of my parents, I now am committed to not owning a car for a very long time.
I know a lot of other people who believe this. Many of them may even get married to other car-fearing, consumption reducing Canadians. Putting their actual annual resource consumption aside, they could end up parents committed to the ideal of reducing resource consumption. They'll dutifully vote for environmental policies in government in the next 50 years, and things will be warm and fuzzy.
When their (and perhaps my) children are born, they'll inherit the earth. It's up for debate what kind of Earth that will be, but for the sake of argument, imagine it's similar to this one. Imagine we're still using up resources too fast, but we've weathered the storm with some really cool technological advances (say, clean and widespread electric cars, among other things).
Let's say me and three of my friends become two of those environmental couples. That's four environmentalists voting for good environmental policies in Canada.
Let's say out of the two couples, one has one child, and the other has zero children.
Wow! In one generation, that's a 75% reduction (not including death rates) in the amount of environmentalists in Canada. Granted, other groups may be decelerating as fast, but I think it's safe to say that environmentalists as a group may end up shrinking in Canada.
If you're in a similar situation, this raises a question. Do you believe in your own values enough to have twelve children? Maybe they won't listen to you, but I bet if you're organized enough (read: wealthy enough) to parent those kids well, they'll wind up respecting you and sharing many of your opinions. If both of the hypothetical couples had an average of 12 kids instead of 0.5, you'd end up with a 600% growth rate of environmentalists. Or if they'd had a more reasonable 4 kids each, that's doubling each generation of new environmentalists. Sure, some will lose the faith. But others will join. Flirt to convert, right!?
This is a question more designed to provoke thought than to guilt anyone into having more kids than they'd planned. What I really want to know is if you believe in your beliefs. Do you value your values? If so, why wouldn't you have 12 kids? It's a dog eat dog world out there, and who's going to represent your values for you when you're dead and gone? But maybe you don't care about your values being represented when you're dead and gone. Then I ask you: do you really believe in your values?