Sustainability of Rangeland Pastoralism--a Case Study from the West Australian Arid Zone using Stochastic Optimal Control Theory

摘要

Optimal economic policies with respect to stocking rate and season of grazing for an arid chenopod pasture type were derived for various starting states under a stochastic optimal control framework. Optimal policies were determined using decision criteria which involved either no discounting of future returns or a discount rate of 6%, and were further evaluated by analysing their long-run economic and ecological consequences. All optimal policies involved either year-long set stocking or restocking. Policies involving seasonal grazing or variable stocking rates were not economically viable at the specified cost levels. Optimal stocking rates increase with the level of forage biomass and the density of adult plants, but decrease with the level of either young or old seedlings when these provide an opportunity for regeneration of degraded range.