Scale, heterogeneity and secondary production in tropical rangelands

Abstract

Tropical rangelands across the world are experiencing land use intensification pressures which are reducing the spatial scale of grazing management units. There are implications of a reduction in scale on environmental heterogeneity and its relationship with secondary production of large herbivores, and on the consequent risks of land degradation. Rangeland managers find it hard to conceptualise these implications and there has been little research to clarify them in the past. This paper will review our current understanding of scale-related effects on livestock production in tropical rangelands and herbivore-plant interactions at patch to landscape scales. We use published information and results from recent empirical studies in northern Australia and elsewhere to elucidate scale-related effects on secondary production. These results indicate that empirical approaches alone will not provide all the understanding necessary for better management of extensive grazing lands that are undergoing intensification and that modelling approaches are important in helping to understand underlying mechanisms driving observed changes. Such modelling approaches need to encompass rangeland systems as complex, adaptive systems where socio-economic factors are just as important as biophysical understanding. We use a conceptual J-curve model to help explain how fragmentation and intensification affects the socio-ecological dynamics of arid and semi-arid grazing lands.



Keywords: fragmentation, grazing, intensification, plant–herbivore interactions, rangelands



African Journal of Range & Forage Science 2004, 21(3): 137–145