The limitations of an equilibrial view of dryland ecosystems (chapter 4) are now recognised. The concept of instability, or disequilibrium, offers an alternative basis for understanding their short-term dynamics. What of long-term changes? As soon as we extend the timeframe of our analysis, it becomes apparent that many dryland ecosystems are in transition between one state and another, or always have been intransition, driven by climate change, the progressive development of soil formations, erosion cycles, and episodic natural events like volcanic eruptions, droughts and floods. Indeed, when the timeframe is lengthened, all ecosystems may be vulnerable to extreme or ‘surprise’ events, whether they emanate from outside or from within the system, as ‘accidents waiting to happen’ (Holling 1987).

For policy purposes, the timescale is important. Because of their frequency, extreme events in the drylands offer a challenging laboratory for working out an appropriate interface between technology and nature. Two main management modes are available (ibid.). The ‘technological–industrial’ mode seeks to control variability and reduce diversity – as in livestock ranching systems. It thereby increases the vulnerability of both ecosystems and production systems (unless financial institutions protect the latter). On the other hand, a ‘low technology’ mode of management – as used by indigenous dryland peoples – seeks to adapt to variability and to exploit diversity. It thereby strengthens the resilience of both the ecosystem and the production system.