In the past few years, the environment has moved to the centre-stage of political debate, and climate change in particular – the most urgent but still only one of a plethora of environmental crises we are facing – has been identified by politicians as the most significant threat facing humanity, greater even than terrorism. It is important to remember, however, that this was not always the case. A mere 30 years ago, those who considered that the way we lead our lives might be causing environmental problems were regarded as fringe thinkers and dismissed as hippies or killjoys. Those who identified the central cause of the environmental problem as the interaction between economic activity and the environment were even rarer. This chapter pays tribute to a few of those thinkers – in different fields of work – who were the first to alert humanity to the seriousness of the problems we were facing.