It is not easy being an environmentalist in the twenty first century. The litany of threats to the global biosphere is long and depressing; I need not rehearse them all here. But it is worth noting that the New York Times reported that the amount of carbon dioxide in the atmosphere has been measured at 400 parts per million, passing what the Times called ‘a long-feared milestone’.1 Climate change is only the most sobering evidence that we live in an age of breached limits, crossed thresholds, and points of seemingly no return.2 As a result, some commentators are arguing that we are entering a new chapter in human history in which ‘the impact of humans [on nature] is now as great, and in some instances greater, than nature’s impact on humans’.3