MANAGING SHEEP GRAZING SYSTEMS IN SOUTHERN AUSTRALIA TO MINIMIZE GREENHOUSE-GAS EMISSIONS - ADAPTATION OF AN EXISTING SIMULATION-MODEL

This study summarises the development of a framework in which changes in the management strategies of sheep grazing systems in temperate Aus tralia can be evaluated in terms of their impact on greenhouse gas emi ssions and financial viability. An exploratory study of a sheep grazin g system at Hamilton, in western Victoria, indicates that reducing emi ssions from some sheep grazing systems in temperate Australia by 20% o ver the next 15 years will require a similar (i.e. 18%) reduction in s tock numbers providing that no other management or technology is used to reduce emissions. This reduction in stock numbers will reduce both farm operating surplus and net cash income by about 15.5 to 17%. The r eduction in net cash income represents a direct reduction in the gener al welfare of the farmer. However, economically viable reductions in e missions may be able to be achieved through changing the time of lambi ng. Spring lambing resulted in returns per unit emissions which were 1 5 to 20% greater than those for autumn lambing. Surveys suggest that a bout two-thirds of all flocks in the area lamb in autumn. Therefore, t here exists an opportunity to reduce emissions by the order of 15 to 2 0% from the region without substantial economic penalties. Overstockin g resulted in both increased net methane and nitrous oxide emissions a nd reduced profitability. The relatively small reductions in stocking rate needed in such situations will reduce greenhouse emissions signif icantly and also may have the effect of reducing soil and vegetation d egradation, thereby improving the sustainability of these enterprises. Implementation of these stocking rate recommendations to reduce green house gas emissions could thus be achieved as part of overall sustaina ble farming.