The framework we have constructed so far for building the economics of biodiversity has had but the briefest of looks into risk and uncertainty. Our account could almost be read as though the socio-ecological world is deterministic. But we know it is not of course. Even in everyday conversation it is customary to take as understood that when someone says, for example, that the next train to London is scheduled to arrive at the station in 50 minutes time, uncertainty is acknowledged, that the speaker says the train is expected to arrive in 50 minutes time.

The term ‘expectation’ has something like ‘average’ built into it.