High birthrate and overpopulation is a massive problem, especially in less economically developed countries. It keeps people in poverty, especially mothers and children, and contributes dramatically to CO2 output, environmental degredation, rising worldwide food prices etc. With improved access to food and medicine and maternal/child health, poorer countries have seen their populations explode in the last 50 years, good examples being China, India, and much of Africa.
Let's say I'm POTUS. I would propose a global program, funded by the richer mostly western countries, to give everyone in poor countries free access to condoms and birth control bills. The main string attached being everyone rich and poor and no matter ethnicity/religion etc, should be given unrestricted access. There's still barriers based on culture and religion for people to actually use the birth control, but it will help. Why spend all this money on carbon taxes etc when doing something like this will make much more of a difference?