The viewpoint that really puts humanity as separate from nature is the one that assumes that the planet can support an unlimited quantity of humans without obliterating nature in the process. How many people do you think the earth can support? 10 billion? 15 billion? At some point we're going to hit a wall. But, thanks to technology, long before we hit that wall most of the plants and animals we take for granted today will be gone.
If we want to preserve a fraction of the biodiversity we have today, at some point soon the human population of the planet will have to stop growing. People who don't have kids are making the rational, forward-looking choice as far as I'm concerned.