Range Management in a Changing Environment: a Southern African Perspective.

Abstract

We address a number of management principles pertaining to temporal and spatial changes in rangeland systems. Both plant community composition, and availability and quality of forage, are temporally variable. The process of community change, at least in southern Africa, appears to differ between humid and arid environments. In humid environments, change follows a relatively gradual and predictable pattern, with both over- and under-grazing resulting in decreased carrying capacity. Factors other than grazing also cause change. In arid environments, change is event-driven, providing the grazier with risks and opportunities to cause or prevent community change from one state to another. Humid and arid rangelands also exhibit different patterns of inter- and intra-seasonal variation in forage availability and quality. In the former, changes, particularly in quality, are relatively predictable, allowing the grazier to match forage demand to supply, thus facilitating stable animal husbandry systems. In arid ranges, the profound change is inter-seasonal forage production, implying unpredictable carrying capacity. Flexibility in livestock numbers is therefore essential. Spatial heterogeneity of rangelands results in patch utilisation and localised deterioration of varying scale. In southern Africa, the traditional response has been fencing, an expensive and sometimes impracticable solution on an extensive scale. Fire and siting of artificial water points or mineral licks are alternative options for redistributing animals. The interaction of spatial heterogeneity with temporal rainfall fluctuations in arid rangelands provides pulses of productivity varying in space, time and magnitude. Settled pastoralism is perhaps unsuited to these environments. Finally, in view of the complexity of rangeland systems, and the paucity of empirical predictions for graziers, we suggest that formalised adaptive management - decision-making from past mistakes and successes - is the most appropriate means for graziers to cope with a changing environment.