Rangelands at equilibrium and non-equilibrium. Recent developments in the debate around rangeland ecology and management

The debate on equilibrium vs non-equilibrium dynamics in pastoral systems emerged in the early 1980s, when economists, ecologists and social scientists began to challenge the widespread claims of overgrazing and degradation in African rangelands and subsequent interventions based on rangeland succession theory and correct stocking rates (for example, Sandford 1982; 1983; Homewood & Rodgers 1987; Ellis & Swift 1988; Abel & Blaikie 1989; Westoby et al. 1989). The debate gained momentum in the early 1990s after two international workshops around emergent new paradigms in rangeland ecology and socio-economics (Woburn I and II), which resulted in the publication of two books, Range Ecology at Disequilibrium edited by Behnke et al. (1993) and Living with Uncertainty edited by Scoones (1994). The ‘new rangeland ecology’ argued that the traditional, equilibrium-based rangeland models did not take into account the considerable spatial heterogeneity and climatic variability of semi-arid rangelands, and that mobility, variable stocking rates and adaptive management were essential for the effective and sustainable utilisation of semi-arid and arid rangeland