Last year was the first time more people in the world lived in cities than in rural areas. But the boom has not come to posh downtown enclaves or middle-class neighbourhoods. It has happened in slums, where one in seven of the world’s population now live – in appalling conditions – and where one in three are expected to live by 2025. From the US to Africa, government officials are wondering how to cope.

Architecture for Humanity, a California-based non-profit organisation, thinks it has the answer. Launched in 1999 as a way of getting architects and designers to help people displaced by the Kosovo war, the organisation has since shifted its focus from disaster and refugee relief to improving slums and other unplanned settlements. “The next war is not going to be about oil, it’s going to be about water, housing, education,” says co-founder Cameron Sinclair. “We want to challenge the creative profession to do something about it. It’s about starting smart growth.”