Ever since Thomas Malthus’ 18^th-century treatise linked overpopulation with conflict and poverty, population growth has been a subject of concern and controversy. But does population decline warrant similar attention? According to Steven Philip Kramer, the subject of this week’s podcast and author of The Other Population Crisis: What Governments Can Do About Falling Birth Rates, it does.

Democracy is fickle. Many of the competing theories on the best ways to foment and consolidate plural, inclusive governance or predict its rise and fall focus on political and economic forces. Yet a small group of demographers have explored population age structure as a catalyst for and reflection of a host of changes in societies that can affect governance.

What are the environmental implications of changing household sizes? A recent article by Mason Bradbury, M. Nils Peterson, and Jianguo Liu, published in Population and Environment, analyzes data from 213 countries over 400 years and finds the average number of occupants per home tends to decline as population grows. This dynamic, they write, indicates that accommodating housing could prove to be one of “the greatest environmental challenges of the twenty-first century.” As countries develop and urbanize, “according to convergence theory, household size decreases (often from greater than five to less than three).” Other cultural shifts, like increasing divorce rates, urban sprawl driven by rising affluence, decreasing numbers of multigenerational households, and larger houses (in the United States, homes more than doubled in size between 1950 and 2002, according to the article) compound the issue. As population growth continues in parts of the world, these trends pose critical questions for conservation and environmental sustainability, since “households are the end consumers of most natural resources and ecosystem services.”

“What’s become clear to me on population is that it’s really a local issue,” said Andrew Revkin in an interview at the Wilson Center. “You get the impression, ‘Oh didn’t we solve that problem?’” And to some extent, demographic shifts around the world are largely heading in the direction people anticipated, with a leveling off mid-century. But “no one really knows what happens then,” he said. “All it takes is a tiny diversion of fertility rates and things could really grow or shrink.”

Compared to East Asia and Latin America, the “demographic transition” in Africa has been slower to date, prolonging periods of rapid growth and creating very youthful populations. But, explains David Canning in this week’s podcast, “the high level of fertility in Africa doesn’t seem to be something that is set in stone.”

Developing countries with youthful populations may have the opportunity to take advantage of a phenomenon called the “demographic dividend,” when a decline from high to low fertility rates leads to slower population growth and a large working age population. But “age structure alone isn’t going to make it happen,” says Jay Gribble of Abt Associates in this week’s podcast.

Population aging and decline are frequently described as a threat to countries’ economic development and social stability. Evocative language, such as “demographic winter” and “graying of the great powers,” portrays the serious consequences that many observers envision as fertility and growth rates decline and the elderly comprise a greater percentage of the population. These concerns reach around the globe, including in Africa, which has the lowest percentage of elderly among the world’s major regions.

As the United States approaches its 2014 deadline for military withdrawal from Afghanistan, one often overshadowed aspect of the conflict is the hard-won progress made by previously marginalized segments of the Afghan population, particularly women, girls, and young people.[Video Below]