The United Nations estimates the world's population could reach nearly 10 billion by 2050. Current tallies put it around 7.6 billion. But where exactly do most of those people live? | NPR

When the global population reaches 9 billion people, how will the Earth cope? Sir David Attenborough explores the changing demographics of Earth over the next 40 years. Thought provoking clip from the BBC's flagship science series Horizon. | Population Matters