My opinion (and this is probably where my signature makes sense) is that the world has enough humans as it is. trust me...I know, it sounds ridiculous.
But I believe that it's the abundance of humans on the planet that create the insane demand for natural resources. Kind of like a virus taking over, where the more there are the harder it is to control.
If you look at the big picture, Humans are like bacteria that's destroying the earth slowly but surely. Sure, you get good bacteria but the amount of bad far surpasses the good.
There have been movies like "The Day the earth Stood still", "Andromeda Strain" (perhaps not this movie so much) and "The Happening" that have been trying to explain this to people in a fictional sense without trying to sound like "green-heads".
Humans are the smartest creatures on the planet but also the dumbest.
I don't plan on having kids for a good reason, because I feel that wanting to bring a child into a world like this is selfish. It's like moving into a house that's inevitably gonna collapse in on itself.
EDIT: sorry I can see how this would sound beyond crazy to a lot of you.