We’re now serving 7 billion on planet earth, according to a UN projection released last week. Some estimates put world population at 16 billion by 2100. Where are all these people going to live?

A few of the faces from the United Nations' Flickr set "One World, 7 Billion Faces"

It’s hard to wrap your mind around a number like 7,000,000,000. That’s an awful lot of zeros. As a start, check out National Geographic’s new project: a year-long series on world population, including a gorgeous image gallery and this simple, three-minute video on the pace of population growth:

The video makes the point that if population growth is a problem, it’s not strictly a problem of space: 7 billion people could stand shoulder to shoulder in roughly the area of Los Angeles, the video claims. The problem is economics: the rise of megacities as more and more rural dwellers look for work in urban areas, the concomitant growth of slums, and the lopsided allocation of resources on our fair planet.

At Housing Revolution, we’re starting a conversation with innovators around the world about how to build better cities, how to use resources more wisely, and most of all, how to house—safely, sustainably, and affordably — the swelling populations of poor urban dwellers in our world, the billions flocking to already teeming cities to find work.

Our first podcast featured Vijay Govindarajan and his $300 House initiative—a design challenge project that aims to create prototypes for affordable, sustainable homes for the world’s poor; in our upcoming podcast we’ll be speaking with Elizabeth Hausler, who’s working to teach earthquake-safe building practices in places like Haiti, Indonesia, and Pakistan, where most earthquake deaths result from cheap, haphazard construction that collapses with people inside.

A lot of what we’ll be talking about here at HR will, like our first two podcasts, address sustainability, affordability, and safety for homes in the developing world. Meanwhile, there’s plenty to say about building and breakneck consumption of resources in America and other big economies. As this recent NPR story (As Population, Consumption Rise, Builder Goes Small) points out, people in growing economies like China and India may try to emulate America as they prosper economically…which means soaring resource use in those countries as well.

A company called Zeta Communities is proposing one way for some Americans to decrease their energy footprint: The company is producing small, modular, “net zero energy” homes on a factory floor near Sacramento, CA — some of them as small as 300 square feet, and stackable. Will American city dwellers buy in?

“The problem is there just isn’t enough cheap energy or water or land for 9 billion or 10 billion people to live the same way,” posits NPR reporter Christopher Joyce. “So what if Americans set a different example? Consume less by living smaller? The Japanese do it. Can small be beautiful in the U.S.? Some people think so.”