Sheep greenhouse gas emission intensities under different management practices, climate zones and enterprise types

Sheep greenhouse gas emission intensities under different
management practices, climate zones and enterprise types

Greenhouse gas emissions (GHG) from broadacre sheep farms constitute ~16% of Australia’s total livestock
emissions. To study the diversity of Australian sheep farming enterprises a combination of modelling packages was used
to calculate GHG emissions from three sheep enterprises (Merino ewe production for wool and meat, Merino-cross ewes
with an emphasis on lamb production, and Merino wethers for fine wool production) at 28 sites across eight climate zones
in southern Australia. GHG emissions per ha, per dry sheep equivalents and emissions intensity (EI) per tonne of clean
wool or liveweight sold under different pasture management or animal breeding options (that had been previously
determined in interviews with farmers) were assessed relative to baseline farms in each zone (‘Nil’ option). Increasing
soil phosphorus fertility or sowing 40% of the farm area to lucerne resulted in the smallest and largest changes in GHG/
dry sheep equivalents, respectively (–66%, 113%), though both of these options had little influence on EI for either clean
wool or liveweight sold. Breeding ewes with greater body size or genotypes with higher fleece weight resulted in 11% and
9% reductions, respectively, in EI. Enterprises specialising in lamb production (crossbred ewes) had 89% lower EI than
enterprises specialising in fine wool production (Merino wethers). Thus, sheep producers aiming for lower EI could focus
more on liveweight turnoff than wool production. Emissions intensities were typically highest in cool temperate regions
with high rainfall and lowest in semiarid and arid regions with low aboveground net primary productivity. Overall,
animal breeding options reduced EI more than feedbase interventions.

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