  Large responses of ecosystems to small changes in the conditions--regime
shifts--are of great interest and importance. In spatially extended ecosystems,
these shifts may be local or global. Using empirical data and mathematical
modeling, we investigated the dynamics of the Namibian fairy circle ecosystem
as a case study of regime shifts in a pattern-forming ecosystem. Our results
provide new support, based on the dynamics of the ecosystem, for the view of
fairy circles as a self-organization phenomenon driven by water-vegetation
interactions. The study further suggests that fairy circle birth and death
processes correspond to spatially confined transitions between alternative
stable states. Cascades of such transitions, possible in various
pattern-forming systems, result in gradual rather than abrupt regime shifts.
