On the flood-prone river islands of Bangladesh, everything is portable. The islands, known as “chars” (pronounced chors), are formed of silt and sand carried down from the Himalayas by the Brahmaputra river. Global warming is accelerating the melting of glaciers, increasing the annual floods. To survive in this ever-shifting landscape, residents of the islands have learned how to be mobile, building houses – and schools – that can be moved at a moment’s notice.