GREENSBURG, KANSAS, IN America’s agricultural heartland, is by no means a greenie enclave. It’s tornado country. On 4 May 2007 an EF5 rated tornado – equivalent to a category 5 cyclone – tore through the area, levelling 95 per cent of the town and killing eleven of its fourteen hundred residents. The sidewalks and sewers were the only thing left behind.

What happened next was unexpected. Greensburg decided to rebuild itself green. Soon after the storm hit, Public Square Communities, a Kansas-based organisation that helps towns build social capital through ‘positive conversations’ about the future, quietly assisted in a process that pulled together the town’s disparate groups to map a vision for recovery. A dream emerged: to become America’s most sustainable and tornado-resilient town, deploying the most advanced clean technologies and encouraging like-minded people to join the effort.