Advancing Quantification of Australia's Livestock Emissions Accounts - Carbon Sinks and Emissions Hot Spots Battle it Out En Route to Net Zero

Abstract

CONTEXT: Rapid decarbonisation is required to mitigate climate change. An overdependence on land-based carbon capture threatens food production, indigenous and local rights, biodiversity, and climate overshoot. Accurate emissions estimates are important for tracking progress towards net zero goals and efficiently determining land requirements to balance un-avoided emissions.OBJECTIVE: Here we examine spatiotemporal greenhouse gas profiles of Australia’s national beef cattle and sheep production including the primary categories allocated by the Australian meat and livestock industry. We assess performance at finer regional disaggregation and incorporate spatially referenced forest carbon cycling. The capacity of National Greenhouse Inventory estimates to represent mitigation progress is explored, and limitations of land-based offset pathways are discussed.METHODS: We combine emission accounting methods with biophysical models to quantify spatially explicit trends in emissions accounts. Annual estimates are produced from 2011-2020 across 46 regions representing >99.5% of Australia’s beef cattle and sheep production.RESULTS AND CONCLUSIONS: We reveal net emissions have reduced from 158 Mt CO2-e in 2011 to 50 Mt CO2-e in 2020. Reductions are associated with declining forest loss whereas other direct sources such as enteric methane are relatively stable and reflect livestock numbers rather than practice change. Our results highlight the power of regionally disaggregated emissions assessments by novelly revealing 12 grazing regions have surpassed net zero accounts in 2020. The scale of forest emission flux suggests strategic forest source-sink shifts have the potential to offset interim livestock emissions. However, access to forest offsets are likely to become competitive and the extent to which net zero objectives can draw on afforestation pathways will be limited by social, environmental and economic constraints. Medium to long-term achievement and maintenance of net zero emission profiles will require progress to be made in reducing direct livestock emissions. Our spatially explicit methods and investigation of National Greenhouse Inventory inputs indicate greater accuracy in industry estimates may be achieved. We recommend direct emission avoidance pathways including halted deforestation and enteric methane avoidance are prioritised rather than relying on offsets to balance accounts.SIGNIFICANCE: Our assessment informs the beef cattle and sheep industries and relevant government organisations of method advancement opportunities to improve the accuracy of national emission estimates, track progress towards net zero commitments and promote efficiency in land-based carbon capture and storage requirements.

Keywords: net zero, greenhouse gas emissions, cattle, sheep, forest sequestration, carbon accounting.