What do we do?
We will probably do nothing, until it is too late.
How do we stop it increasing?
Birth control, more birth control, still more birth control.
How do we reduce it?
Abortion, more abortion, and still more abortion.
What will happen if we don't?
We won't. The likely result will be either a great increase in pain and suffering due to disease and famine, or a nuclear holocaust.
Should we care?
Yes, we should. But the people who have the ability to do something won't.
Sorry for the pessimism. But that's how I see it.