Watch the video of the 4th Earth Debate, hosted by the Museum on 11 April 2012. The debate focused on how we can feed the anticipated global population of 9 billion people in 2050 and the changes that the UN's Rio+20 Earth Summit in June 2012 will need to instigate for it to be possible. This was the 4th and final Earth Debate in the Museum's Attenborough Studio, but you can continue the discussions online at www.nhm.ac.uk/natureplus/thread/5669