Professor John Cleland of the London School of Hygiene & Tropical Medicine talks about the central role of family planning for tackling the linked challenge of rising global populations and climate change. He tells why a reduction of unwanted pregnancies is needed - especially in sub-Saharan Africa - as the means of relieving poverty and improving health for all. Dr Alex Ezeh, Executive Director of the African Population and Health Research Centre in Nairobi discusses the central role of Africa in population strategies for the planet. Professor Paul Wilkinson of the London School examines the real hope that rising populations - which limit progress in cutting carbon emissions and which threaten basic health - can be contained to offer a better future for everybody.