Tackling growing population and consumption must be part of protecting environment, says Royal Society "There are at least 200 million women in the world who have an unmet need for contraception," he said. That is to say if someone was offering them the means, they would want it. It does not mean they don't want children, they want the opportunity to space their children out. It is extremely good value for aid because it has such a good knock-on effect for women and children. Sir John also said consumption needs to be addressed in the developed world by encouraging people to use less fossil fuels. This could be done through switching to low carbon energy, improving technology and change in behaviour. Developing countries will be building the equivalent of a city of a million people every five days from now until 2050, but this can be part of the solution by making sure these cities are sustainable by providing public transport and efficient buildings. Sir John said the way that Gross Domestic Product should be replaced by a new measurement that takes into account natural capital in order to incentivise Governments to protect the environment. He said tackling the growing population, rising consumption and developing a new international measurement to encourage green growth must be priorities for the Rio+20 Earth Summit in June. The world now has a very clear choice. We can choose to address the twin issues of population and consumption. We can choose to rebalance the use of resources to a more egalitarian pattern of consumption, to reframe our economic values to truly reflect what our consumption means for our planet and to help individuals around the world make informed and free reproductive choices. Or we can choose to do nothing and to drift into a downward vortex of economic, socio-political and environmental ills, leading to a more unequal and inhospitable future.