I don't mean to be an idiot, but at this point all life saving charity should aim to secure a reduction in population growth to offset the lives saved. Being merely a humanitarian is a moral luxury with an environmental cost.
Arguably, Gates' grants works towards that. It will result in better agriculture, in the future leading to mechanization -- which means people moving to cities.
(+) Let us leave discussions of e.g. reintroducing the plague to Al Qaeda. 1/2 :-)
Edit: I might add that I think human lives are worth the environment, inside sane limits. Pollution go down with increased wealth, anyway.