Calm amid chaos: a child in a camp for Rwandan Hutu refugees photographed by Sebastião Salgado  Around half the world's 50 million refugees are children under the age of 18, according to recent figures published by the United Nations High Commission for Refugees. Forced away from their homes - and in many cases, their parents - by war or civil unrest, they live in appalling conditions in camps and orphanages, where they are vulnerable to disease and recruitment as soldiers.  Sebastião Salgado, who has spent decades photographing migrant populations around the world, says that while it is clearly children who suffer most from being displaced, they rarely show it. In Afghanistan, the Balkans, Sudan, Sierra Leone, Angola, Burma and the far east, it is invariably children who approach him first, smiling and waving, crowding to get into the picture. In Mozambique, photographing a population displaced by civil war, Salgado was overwhelmed.  "Wherever I went, I was surrounded. Finally, I said to them, 'I'm going to sit here. If you want me to take a picture of you, line up.'"  Taking them on their own, rather than in an excitable crowd, Salgado caught something of each child's personality. The pictures were calmer, and more candid for it. "For a brief moment," he says, "they were able to say, 'I am'."  This month, an exhibition of Salgado's photographs of children, taken in the 1990s, opens at the Barbican centre in London.  How much has changed since they were taken? In the past decade, the number of child refugees worldwide has risen and fallen, and risen again. Last year, more than four million children returned to school in Afghanistan - many of them girls who had never before set foot in a classroom. Unicef has made some progress worldwide with polio vaccination and Aids education programmes. It has also demobilised large numbers of child soldiers, many of them recruited from refugee camps in Sierra Leone, Sudan, Angola and Sri Lanka - although in this area there is still a long way to go.  A photograph, Salgado admits, cannot tell us everything about these harsh realities; it is not analytical in that way. But what it does show is a moment of peace on a particular day in a particular and difficult life.  · Exodus, an exhibition of photographs from Sebastião Salgado's Migrations and Children series, is at the Barbican centre, London EC2, in partnership with Amnesty International, running from February 13-June 1. Buy a special Amnesty International ticket and £1 will be donated directly to Amnesty International (joinamnestynow.com).
They have no home, sometimes no parents, and their future is hazardous. But Sebastião Salgado's photographs capture them in a moment of peace.