rationalskepticism.org

With such rapid population growth in the poorest region of the world I expect to see massive famines and much more social upheaval than we see today. If we (the rich bastards of this planet) don't want to get swamped with refugees and asylum seekers we'd better anticipate or help to fix this problem as best we can.
Besides the moral obligation one might feel towards helping those nations manage their population size as best as possible, it's simply in our own best interest.

Or place a massive electrified fence around Africa..