Today we overshoot ourselves. We’ve used up in less than eight months the resources that the earth provides in a year. In 2012 it took us until 22 August. Only ten years ago we were able to make do for an extra month. We already treat the earth as if it were 50 per cent bigger than it is. And if everyone lived as we do in Britain, the planet would need to be 3.5 times its present size.