The damming of a river that feeds the world’s largest desert lake could lead not only to less drinking water for thousands of Kenyans, but international conflict between tribes for what little water remains.

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.

How to stop climate change while expanding energy production is one of the biggest challenges in global development. Doing so requires all kinds of improvements in efficiency – from reducing the amount of electricity lost in transmission to better motors and lightbulbs. But, as demonstrated by recent efforts in the Pentagon, changes to how people work may be the lowest hanging fruit.

Population projections undergird many important policy decisions, from the U.S. government’s Feed the Future program to the Sustainable Development Goals. But they’re not as straightforward as they appear. Demographers often base their estimates on complicated assumptions that aren’t obvious to the end user.

“There is no magic bullet or solution to resolving climate change quickly,” said the Population Reference Bureau’s Jason Bremner at the Wilson Center on October 28. “Our next 100 years will be far different from the last 100 or the last 1000…and it has become clear that nations will have to pursue many strategies in order to reduce emissions, build resilience, and adapt.” [Video Below]

“We don’t know the reason for the death of fish in downstream villages,” Hamberton Nongtdu, a mine owner from the northeastern Indian state of Meghalaya, told me.