By Irene Pedruelo for Policy Innovations

He has worked side by side with Lord Norman Foster for almost 40 years, but David Nelson doesn’t preach about architecture. Instead, he prefers conversation. As the joint head of design at Foster + Partners architecture and design studio, he has worked on some of the studio’s most emblematic projects: Masdar City in Abu Dhabi, the new German parliament in Berlin, the Bilbao metro in Spain, and the Florence high-speed railway station. Nelson is reluctant to speak in first-person when talking about the work he does. This decision, I will learn in our hour-long conversation on the future of cities, is not trivial but a direct reflection of his understanding of architecture and urban design as a collective endeavor: “We’re a lot of people, and we all work very closely together. I’m just a representative.”

I think in the end, it all comes down to how we manage ourselves as human beings. Maybe when we get that right, we might be able to have solved some of these problems.

IRENE PEDRUELO: The UN has estimated that by 2050, 66 percent of the world’s population will live in cities. Managing urban areas has become one of the top development challenges of the 21st century. In this context, there’s been a lot of conversation, a lot of hype, around eco-cities and sustainable cities, so let’s start by asking: What are sustainable cities?

DAVID NELSON: Being sustainable is to say: if we are going to survive on this planet for as long as we can, the way we live our lives has to change to reflect the reality of what we’ve got. The world’s resources are finite, and if you look at the lifestyle of people in the United States, to maintain that way of life we need about five planets. In Europe it’s about three or four. In the end, it boils down to—we need to do more with less. With those numbers of people—70 percent— living in cities, clearly the focus for this issue is in cities.