Our population is growing and could exceed 9 billion within the next four decades. With 400,000 people born every day, how many people can live on planet Earth? Esteemed naturalist Sir David Attenborough takes a look at the problems we face as the world population continues to grow: shrinking water reserves, food shortages, and dwindling natural resources. Among the experts interviewed is UBC professor William Rees, who talks about how our current rate of consumption far exceeds what the planet can supply. But a bleak future is not inevitable. Countries around the world are coming up with solutions, while improvements in social policy and global cooperation offer hope.