Optimising mixed-grazing strategies for semi-arid Australian rangelands

Currently in semi-arid Australian rangelands properties produce mainly beef and wool on marginal lands. A major area of concern is grazing pressure. Kangaroos are considered to have a considerable impact on grazing pressure, and for that reason they are often considered pests by landholders. It has been thought that converting from farming European stock to native wildlife would have environmental benefits. The commercial benefits from the change are unclear. Through construction of a plant-herbivore model, the dynamics of cattle, sheep and kangaroo commodities are examined. Simulations were constructed so as to estimate the expected value for each and the correlation between the different commodities. Portfolio analysis using mean-variance, average value-at-risk, and multi-objective optimisation projects were used to analyse different allocations of forage to each herbivore. The effect of an enforced reduction in methane emissions is also explored. From the analysis it seems that diversification of herbivores (including kangaroos) is optimal on marginal lands, for the risk adverse, and to reduce methane emissions.