Gen. Michael V. Hayden, the director of the Central Intelligence Agency, yesterday described three troublesome trends that distinguish this century from the last, and the exploding populations of poor places topped his list. Interestingly, energy shortages (and climate change) were not on his list. (The other trends were growing divisions between the United States and Europe and China’s emergence.) I’ve sent a query to the agency’s press office to find earlier statements on fossil fuels and security.

Today, there are about 6.7 billion people sharing our planet. By midcentury, the best estimates point to a world population of more than 9 billion. Most of that growth will occur in countries least able to sustain it, a situation that will likely fuel instability and extremism, both in those areas and beyond.