Some random thoughts:
1-. You will die, your kids will die, your kids kids will die and so on. No matter how good or bad the climate is or advanced is the medicine, they will eventually die.
2-. You will struggle in life, your kids will struggle in life, your kids kids will struggle in life, no matter how good social security, free education or free medicine, all will struggle, and it was the same for all of your ancestors. They may have different struggles than you, the same as you have different struggles than your ancestors, but they will struggle, and life will be hard. There is no period in the history of human kind were people did not struggle to live. There have been more peaceful moments, like right now, when hunger is at the lowest ever worldwide, but it's never been easy.
3-. If we reduce the problem to a basic Darwinian premise; the survival of the fittest, the fittest are the people having kids, as basic as that is. Those are the people ensuring their genes pass to the next generation; people in underdeveloped countries are more fit than people in developed countries, and they are slowly, but surely, invading those countries. Latin americans are more fit than whites in the USA, eastern europeans are more fit than western europeans, and people from muslim countries are more fit than both. Those populations are not only growing because of mass immigration, they are growing because they are having more kids.
4-. I don't believe for a second any of you saying you are not having kids because of climate change. You have your own reasons for not having kids, and I fully respect them, and maybe climate change is a factor, but it's a factor way, WAY down the list of reasons for not having kids. You may disagree with me, and it's fine, just wanted to tell you I just don't believe it, and I'm calling bullshit.
5-. A scary thought for some:
I'm a conservative and catholic and pro-life, I am expecting my 5th child and am 31, so I have room for a couple more kids. My friends that are conservative, catholic and pro-life have much more kids than those who aren't. Those who aren't, have less kids, if any at all.
I've read statistic that 7 out of 10 kids hold about the same political views as their parents. Think about it, why is it that so many of you, on this heavily liberal leaning forum (sorry for generalizing), have conservative parents? Judging by some threads, especially the thanksgiving ones, it's a lot. And those who have, how many have conservative brothers or sisters as well? Again, a lot. Do those conservative brothers or sisters have more kids than you?
This is the reason religions and conservatism will never cease to exist. If liberals aren't having kids, then they have a HUGE job to do if you want to convince the next generations, kids raised in conservative families, of their values and ideas.