The world's population will reach seven billion this year. Can the Earth sustain this many people and is reproductive freedom a fundamental liberty? What will the future hold for a crowded planet? In this film, Professor John Guillebaud, Population Matters; Sara Parkin, Forum for the Future; Fred Pearce, author of 'Peoplequake'; and Sir Tony Wrigley, Cambridge Group for the History of Population and Social Structure debate the topic. This event forms part of the Cambridge Festival of Ideas (cam.ac.uk/festivalofideas) on Tuesday 25 October 2011.