It's tough because it would require literally every single person caring more about a nebulous concept of "humanity" and "longevity" than they would themselves, their families, and the next 40 years of world issues. A seriously smart human race would self-limit birthrates to replacement rates and focus efforts on long-term survival mechanisms (asteroid monitoring and redirection, wildlife and environmental management, wide-ranging health care, etc.) but it's so hard to get people to get on board.