The leading article of the January edition of this year's National Geographic was about this population milestone. The article made some interesting observations, higher levels of industrialisation correlated with lower birthrates, although they noted that the more industrialized nations consumed more resources. I was impressed by this byline: "People packed into slums need help, but the problem that needs solving is poverty, not overpopulation." (National Geographic, Jan 2011, 61)
This byline from National Geographic sums up for Christians the correct ethical focus, the problem is not 'too many people' but 'too many people being sinful in their use of resources'. The difficulty is coming up with political, personal and communal ways of sensibly using our resources without buying into a 'Green' ideology.