Patch dynamics is a new, potentially unifying mechanism for the explanation of tree-grass coexistence in savannas. In this scale-explicit paradigm, savannas consist of patches in which a cyclical succession between woody and grassy dominance proceeds spatially asynchronously. The growing ecological and economic problem of shrub encroachment is a natural transient phase in this cycle. Keywords: Acacia mellifera, cyclical succession, individual-based simulation model, patch scale, scale, shrub encroachment, size-frequency distributions, temporal autocorrelation, tree-grass coexistence.