Bill Gates just addressed this [1], showing the faulty thinking behind this idea that saving lives is ultimately bad for the earth.
"It may be counterintuitive, but the countries with the most deaths have among the fastest-growing populations in the world. This is because the women in these countries tend to have the most births, too.
This pattern of falling death rates followed by falling birth rates applies for the vast majority of the world. Demographers have written a lot about this phenomenon. The French were the first to start this transition, toward the end of the 18th century. In France, average family size went down every decade for 150 years in a row. In Germany, women started having fewer children in the 1880s, and in just 50 years family size had mostly stabilized again. In Southeast Asia and Latin America, average fertility dropped from six or seven children per woman to two or three in a single generation, thanks in large measure to the modern contraceptives available by the 1960s.
Because most countries—with exceptions in sub-Saharan Africa and South Asia—have now gone through this transition, the global population is growing more slowly every year. As Hans Rosling, a professor at the Karolinska Institute in Sweden and one of my favorite data geeks, said, “The amount of children in the world today is probably the most there will be! We are entering into the age of the Peak Child!”"
Saving lives will improve humanity and -- as humanity has discovered -- actually contributes to fewer births. This is one of the reasons we see shrinking populations in 25 nations including Japan, Ukraine, Italy, Greece. [2]
The reality is that saving lives counterintuitively decreases population through lower birth rates, which may ultimately help the earth.
Also, observe that the world is at its highest population today, and yet, billions of humans are totally resource-secure. Why this counter-intuitive phenomenon? It's largely thanks to technological advancements in farming and genetics. There is no reason to believe this trend will not continue.
[1]: http://annualletter.gatesfoundation.org/?cid=bg_gn_ll0_01202...
[2]: http://en.wikipedia.org/wiki/Population_decline