I have no idea what birth rates have to do with milking ducks, and especially why it matters in the context of allowing folks to use a drug less harmful than alcohol if they so desire, but shout off, dude, you do you.

The world population continues to barrel upwards at a likely-unsustainable rate, don't worry, we'll find plenty of people to live in "the west" even if people are opting out of raising screaming, expensive children themselves (or maybe being opted out of it - many folks I know want children for various reasons, but can't afford to even birth them, let alone raise them).