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Evaluating the cost-effectiveness of GHG mitigation in the dryland agricultural sector is needed in terms of designing and implementing detailed and efficient mitigation programs, which is currently rarely covered by the literature. In this paper, we use a parametric directional distance approach to explore the farm-level abatement potential and cost (shadow value) of GHG for dryland farms in southwestern Australia. The study indicates that dryland agriculture could abate substantial GHG emissions and save agricultural inputs simultaneously. For the years 2006–2013, the average abatement potential ratios fluctuated between 17 and 33%, with a mean value of 21%. The mean shadow price of dryland agricultural GHG was $17.60 per tonne CO2-e in 2013 Australian dollars. In general, the analysis supports that reducing GHG in dryland agriculture is relatively cost-effective. [ABSTRACT FROM AUTHOR]

Farming systems face dual pressures of reducing greenhouse gas (GHG) emissions to mitigate climate change and safeguarding food security to adapt to climate change. Building soil organic carbon (SOC) is proposed as a key strategy for climate change mitigation and adaptation. However, practices that increase SOC may also increase nitrous oxide (N 2 O) emissions, and impact crop yields and on-farm income. A comprehensive assessment of the effects of different management practices on trade-offs between GHG emissions and agricultural systems profitability under climate change is needed. We aimed to: (1) analyze the long-term trends of SOC and N 2 O emissions, and ascertain whether the croplands of the study region are net GHG sources or sinks under climate change; (2) quantify the GHG abatement on a gross margin basis; (3) identify effective management practices that could achieve a win-win strategy; and (4) investigate sources of uncertainty in estimates of GHG emissions and gross margins under climate change. APSIM was used to simulate the effects of three crop residue retention rates (10%, 50% and 100%), and six representative crop rotations (wheat-canola, wheat-field pea-wheat-canola, wheat-field pea-wheat-oats, wheat-wheat-barley, wheat-wheat-canola, and wheat-wheat-oats) under two Shared Socio-economic Pathways scenarios (SSP245 and SSP585) using climate projections from 27 GCMs. GHG emissions and gross margins from 1961 to 2092 were assessed across 204 study sites in southeastern Australia. Our results showed that residue retention can turn the soil from a carbon source (10% retention, 304–450 kg CO 2 -eq ha−1 yr−1) to a carbon sink (100% retention, −269 ∼ −57 kg CO 2 -eq ha−1 yr−1), and the potential of carbon sequestration was partly offset by concomitantly increased N 2 O emissions. The wheat-wheat-canola rotation with full residue retention was shown to be a win-win solution with both large potential of GHG abatement and high gross margin compared with other rotations. Spatial analysis showed that the southeastern part of the study region, with higher rainfall, had higher gross margins, while the drier northwestern part had greater GHG emission reduction potentials. Although climate change led to increased GHG emissions and decreased yields for some crops, these adverse effects were overweighed by the higher SOC and yield advantages from full residue retention. This study emphasizes the significant potential for agronomic management to maximize gross margin and reduce GHG emissions under climate change in southeast Australia. Results from this study could be used by farmers and policymakers to mitigate climate change without compromising agroecosystem profitability. [Display omitted] • APSIM was used to simulate the effects of residue retention and crop rotation on GHG emissions and gross margins. • Retaining all crop residues could turn the soil from a carbon source to a carbon sink, and benefit gross margins. • Enhancement of residue retention on GHG abatement overweighed adverse effects of climate change under SSP245 and SSP585. • The wheat-wheat-canola rotation was the most beneficial in terms of GHG mitigation and profitability compared with others. [ABSTRACT FROM AUTHOR]

• We model operational and embodied GHG emissions for Australia's built environment. • The scope includes residential and commercial buildings. • A high ambition scenario delivers a 94% reduction in emissions compared to BAU. • Includes renewables, electrification, efficiency and material replacement. • Novel pathways analysis highlights options for net zero and net negative emissions. Achieving net zero operational and embodied greenhouse gas (GHG) emissions in the built environment is recognised in Australia and globally as a key strategy to address climate change and achieve the United Nations Sustainable Development Goals (SDGs). However, gaps in knowledge remain regarding potential national pathways to achieve this outcome in Australia. This study further extends and applies a national-scale integrated macroeconomic simulation model to explore coherent pathways to net zero emissions in the built environment sector by 2050. The scope of the study includes residential and commercial buildings and both operational and embodied emissions. It applies scenario analysis incorporating different levels of climate ambition, including a shift to renewable energy, electrifying buildings, improving energy efficiency and replacing carbon-intensive materials. We find that a high ambition scenario (Scenario 2) delivers a 94% reduction in GHG emissions by 2050 when compared against business-as-usual, placing a net-zero target within reach. Improvements on Australia's SDGs performance are also attained. Through subsequent pathways analysis we find that achieving net zero or even net negative operational and embodied emissions is feasible with more ambitious action in key areas, including increasing the share of mass-timber buildings and reducing end-of-life losses in sequestered carbon. [ABSTRACT FROM AUTHOR]

Abstract: Pricing greenhouse gas emissions is a burgeoning and possibly lucrative financial means for climate change mitigation. Emissions pricing is being used to fund emissions-abatement technologies and to modify land management to improve carbon sequestration and retention. Here we discuss the principal land-management options under existing and realistic future emissions-price legislation in Australia, and examine them with respect to their anticipated direct and indirect effects on biodiversity. The main ways in which emissions price-driven changes to land management can affect biodiversity are through policies and practices for (1) environmental plantings for carbon sequestration, (2) native regrowth, (3) fire management, (4) forestry, (5) agricultural practices (including cropping and grazing), and (6) feral animal control. While most land-management options available to reduce net greenhouse gas emissions offer clear advantages to increase the viability of native biodiversity, we describe several caveats regarding potentially negative outcomes, and outline components that need to be considered if biodiversity is also to benefit from the new carbon economy. Carbon plantings will only have real biodiversity value if they comprise appropriate native tree species and provide suitable habitats and resources for valued fauna. Such plantings also risk severely altering local hydrology and reducing water availability. Management of regrowth post-agricultural abandonment requires setting appropriate baselines and allowing for thinning in certain circumstances, and improvements to forestry rotation lengths would likely increase carbon-retention capacity and biodiversity value. Prescribed burning to reduce the frequency of high-intensity wildfires in northern Australia is being used as a tool to increase carbon retention. Fire management in southern Australia is not readily amenable for maximising carbon storage potential, but will become increasingly important for biodiversity conservation as the climate warms. Carbon price-based modifications to agriculture that would benefit biodiversity include reductions in tillage frequency and livestock densities, reductions in fertiliser use, and retention and regeneration of native shrubs; however, anticipated shifts to exotic perennial grass species such as buffel grass and kikuyu could have net negative implications for native biodiversity. Finally, it is unlikely that major reductions in greenhouse gas emissions arising from feral animal control are possible, even though reduced densities of feral herbivores will benefit Australian biodiversity greatly. [Copyright &y& Elsevier]