Accurate quantification of greenhouse gas (GHG) emissions from grazing livestock systems is essential for informing climate mitigation strategies and improving the robustness of national reporting frameworks. Emissions from grazing systems vary across agroecological zones, climate variability, production dynamics, the components included within the system boundary and time frames. This study used a systems approach to assess the influence of annual and running multi-year time steps on total GHG emissions and emissions intensity (EI) of livestock production across ten years. A partial pre-farm to farm gate life cycle assessment (LCA), with the boundary representing the whole-farm level, was applied to two case studies in Northeastern Victoria (NEV) and in Central-Western Queensland (CWQ). The NEV property recorded higher average annual emissions (11,039 t CO₂-eq) than CWQ (2096 t CO₂-eq), with substantially lower interannual variability (Coefficient of variation (CV) = 7% vs. 37%). Emissions intensity (EI) of beef production averaged 13.0 kg CO₂-eq/kg liveweight at NEV and 10.8 kg CO₂-eq/kg at CWQ, but variation was much greater at CWQ (CV = 35.7%) than NEV (CV = 15.1%). Running three- and five-year averages smoothed short-term fluctuations driven by climate and management responses to climate and market changes. A systems approach is needed to capture all factors affecting farm emissions. Temporal smoothing can provide more consistent emissions estimates to assess reductions over time, with a longer period required to detect change with a desired level of confidence under more variable conditions. Farm-scale accounting should consider system-specific temporal resolution to inform mitigation and reporting frameworks. • GHG emissions assessed in temperate and rangeland grazing systems over 10 years. • Partial pre-farm to farm-gate LCA used with detailed, longitudinal farm records • Multi-year averaging stabilized emissions in temperate but not rangeland systems. • Enteric methane drives rangeland variability, inputs drive it in temperate systems. • Temporal aggregation effects differ by system, affecting GHG reporting precision.
Peralta et al. (Thu,) studied this question.