There is widespread agreement, and untold publications, that argue urbanization is the defining issue of our time. There are more cities, both large and small, and more people living in those cities than anytime in human history.

With UN demographers more certain than ever that global population will reach between 10 and 12 billion by the end of the century, the challenge of building a sustainable future seems daunting. But according to Wolfgang Lutz, founding director of the Vienna-based Wittgenstein Center for Demography and Global Human Capital, these projections miss one crucial variable: increasing levels of education. [Video Below]

Much of the time, discussion about climate change is focused on the future – How bad will it be? Will it lead to more conflict? Who will be most vulnerable? But it is in fact a current phenomenon. The climate system is already, for all intents and purposes, irrevocably changed and millions of lives have been changed along with it.

“We have a fairly unique moment in the history of the world,” said Steven Philip Kramer, a professor at National Defense University, at the Wilson Center on April 17. “There’s never been a time when people have voluntarily produced fewer children than is necessary for sustaining the population.” [Video Below]

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.”