“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.”

Revkin, who runs The New York Times’ Dot Earth blog, has been writing about population for years, often in the context of environmental limits and resource scarcity. “Back in the 60s the ‘population bomb’ was kind of this grand threat to resources and hunger threat,” he said. “Now when you look around the world, as some demographers have described it to me, there are ‘imploders’ and ‘exploders.’”

While some regions have stopped growing entirely and are even shrinking, others, like sub-Saharan Africa, the Middle East, and parts of Asia, are still growing rapidly. This can create local resource scarcity and also put more people in the path of disasters.

“In many of the areas around the world…where you have high fertility rates, you also have high exposure to natural hazards, whether it’s earthquakes in Sumatra, or heat waves, or extreme drought in parts of Africa, or flooding events,” he said. The population of Tacloban City, the capital of the province struck most directly by Typhoon Haiyan in the Philippines, almost tripled over the last 40 years. One in three homes had wooden exterior walls; one in seven, grass roofs. “So you if you’ve got this burst of population growth in the next 30 or 40 years and a lot of urbanization, again, in areas that are vulnerable to disasters, you’re setting up a really bad situation.”

Revkin spoke at the Wilson Center January 24 on a panel of environmental journalists previewing the biggest stories of 2014, including the potential for more natural disasters as climate change continues to alter conditions.

“Population was long perceived as mainly an issue in terms of people’s resource appetites: more people means more demand for stuff,” he said. “But in vulnerable places it actually means a bigger exposure to hazard.”