To play a devil’s advocate (I don’t think I’m right, it’s just the next obvious thought), the life you save produces another two, and after few steps you still can’t. Animal charities, and I feel sorry for this comparison, in areas without controlled population tend to overwhelm themselves to the point where the charity dilutes into conditions indistinguishable from natural.
You may say, well, then help fixing the root cause. That’s right, but you have to find true one and fix it, and both is hard. Much easier to calm yourself by a donation to people who you prefer to believe to understand more.
One point is that when people have secure lives, the birth rate plummets. When your only capital is children, you make more children. By meeting the needs of the worst off, they have fewer children, not more.
I'm sure there were other points made, but I don't want to attempt to restate those from my shaky memory of what I read more than a year ago.
You may say, well, then help fixing the root cause. That’s right, but you have to find true one and fix it, and both is hard. Much easier to calm yourself by a donation to people who you prefer to believe to understand more.