The solution is simple enough... people in these overpopulated countries need to quit having so many babies (Rick F.)

One solution, and not a very humane one as Freda has remarked. You could also look at it another way: Our birth rate once was as high as is now theirs. We now live in more densely populated areas than they do. Our birth rate went down as the riches available to a larger percentage of the population increased. So here's another take at the solution:

Make the riches of the world available to them too and the birth rates will go down as ours did.

Wolfgang