I very much doubt that

Blacks are an r-selected population, designed to have an insane birthrate. Given the resources, they will breed until the resources run out and they start dying of starvation again. We see this happening in Africa right now with all our foreign aid money and charity. It's complete madness.

The white population in South Africa used to be the majority. Now they're just 10% of the population, thanks largely to birthrates over the last 100 years. 
You might want to save every single life, I would rather save the life of civilization itself, since that will lead to even greater bounty in the future. 

If you don't want to abort them, we could try castrating them instead