Should Americans worry that there are 300,000,000 of them now?

Don Boudreaux quoting John Tierney's NYT column of October 14:

“Overpopulation” is history’s oldest environmental crisis, and it’s the most instructive for making sense of today’s debates about energy and climate change. It’s a case study of intellectual arrogance, and of the perils of putting too much faith in a “scientific consensus” of experts infatuated with their own forecasts.

Four decades ago, scientists were so determined to prevent famines that they analyzed the feasibility of putting “fertility control agents” in public drinking water. The physicist William Shockley suggested using sterilization to impose a national limit on the number of births.

Planned Parenthood’s policy of relying on voluntary birth control was called a “tragic ideal” by the ecologist Garrett Hardin. Writing in the journal Science, Hardin argued that “freedom to breed will bring ruin to all.” He and others urged America to adopt a “lifeboat ethic” by denying food aid, even during crises, to countries with rapidly growing populations.

Russell Roberts quoting David Henderson in the Wall Street Journal:

In 1968, long before Julian Simon popularized the idea that population growth is good, [2006 Economics Nobel Prize winner] Mr. Phelps made the same argument: The more people there are, the more ideas are developed, and ideas, once developed, can be transferred to others at almost no cost.

UPDATE: Posner and Becker join the debate.