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Supporters of hydrogen energy urge scaling up technology and reducing costs for competitiveness. This paper explores how hydrogen energy technologies (HET) are perceived by Australia's general population and considers the way members of the public imagine their role in the implementation of hydrogen energy now and into the future. The study combines a nationally representative survey (n = 403) and semi-structured interviews (n = 30). Results show age and gender relationships with self-reported hydrogen knowledge. Half of the participants obtained hydrogen information from televised media. Strong support was observed for renewable hydrogen, while coal (26%) and natural gas (41%) versions had less backing. Participants sought more safety-related information (41% expressed concern). Most felt uncertain about influencing hydrogen decisions and did not necessarily recognise they had agency beyond their front fence. Exploring the link between political identity and agency in energy decision-making is needed, with energy democracy a potentially productive direction. • Hydrogen's strongest appeal to Australians is its benefit for climate change mitigation. • Although widely accepted, there is limited knowledge about hydrogen in terms of how it is produced or used. • The more people know about hydrogen, the more willing they are to participate in the decision-making process. [ABSTRACT FROM AUTHOR]

Wetland area and condition are declining globally despite their importance to climate change mitigation and biodiversity. Introduced ungulate species are contributing to the global decline. Their impacts on wetlands are widespread and varied, however poorly understood. We summarise global impacts of introduced unmanaged and domesticated ungulates on wetlands highlighting potential outcomes of their removal. We place an emphasis on Australia due to the disproportionate impacts of ungulates on wetlands and potential for emerging carbon and biodiversity markets to incentivise private investment in wetland conservation and restoration. Our Systematic Literature Review assessed impacts of cattle, pigs, horses, deer, buffalo, sheep, camels, and other ungulates on wetlands. There were 372 relevant resources from 35 countries, with highest representation from Australia and the United States. The majority related to cattle (29 %) and pigs (19 %). More impacts were reported in freshwater wetlands (51 %) than marine (19 %). A quarter of studies related to riparian habitats. Ungulate impacts varied geographically and among climates. More studies reported soil damage, weed dispersal, decreased vegetation cover, and woody vegetation suppression than neutral or positive changes in these metrics. Decreases in richness and abundance of native flora and fauna were more frequently reported than increases. Of 33 studies reporting wetland carbon impacts, 24 reported increased CO 2 emissions due to loss of soil carbon or vegetation biomass. Ungulate exclusion from wetlands could enhance carbon stocks and biodiversity, however further studies comparing wetland typologies and carbon dynamics are needed to quantify levels of enhancement given differences in ungulate species and environments. • Wetlands are declining despite their importance for climate change and biodiversity. • Impacts of feral and domesticated ungulates on wetlands vary by ecology, region, climate, and wetland type. • Ungulates damage soils and reduce ground cover, which may increase carbon emissions. • Reported ungulate impacts on flora and fauna are most often negative, but effects depend on taxa and region. • Control of ungulates in wetlands may support wetland conservation and restoration. [ABSTRACT FROM AUTHOR]

The soil security concept has been put forward to maintain and improve soil resources inter alia to provide food, clean water, climate change mitigation and adaptation, and to protect ecosystems. A provisional framework suggested indicators for the soil security dimensions, and a methodology to achieve a quantification. In this study, we illustrate the framework for the function soil carbon storage and the two dimensions of soil capacity and soil condition. The methodology consists of (i) the selection and quantification of a small set of soil indicators for capacity and condition, (ii) the transformation of indicator values to unitless utility values via expert-generated utility graphs, and (iii) a two-level aggregation of the utility values by soil profile and by dimension. For capacity, we used a set of three indicators: total organic and inorganic carbon content and mineral associated organic carbon in the fine fraction (MAOC) estimated via their reference value using existing maps of pedogenons and current landuse to identify areas of remnant genosoils (total organic and inorganic carbon) and the 90th percentile for MAOC. For condition we used the same set of indicators, but this time using the estimated current value and comparing with their reference-state values (calculated for capacity). The methodology was applied to the whole of Australia at a spatial resolution of 90 m × 90 m. The results show that the unitless indicator values supporting the function varied greatly in Australia. Aggregation of the indicators into the two dimensions of capacity and condition revealed that most of Australia has a relatively low capacity to support the function, but that most soils are in a generally good condition relative to that capacity, with some exceptions in agricultural areas, although more sampling of the remnant genosoils is required for corroboration and improvement. The maps of capacity and condition may serve as a basis to estimate a spatially-explicit local index of Australia's soil resilience to the threat of decarbonization. • Methodology based on the soil security assessment framework. • Quantification of the capacity and condition of the soil to store carbon. • Spatial estimation of the utility to support carbon storage for three indicators. • Australia has low capacity, but overall good condition to store carbon. • Intensive up-to-date sampling is required to corroborate the results. [ABSTRACT FROM AUTHOR]

• Estimates of the time of emergence of climate change (ToE) for Australian rivers. • Stochastic data generation helps to better define baseline variability. • Uncertainty in ToE represented by 37 CMIP6 projections and 3 emissions scenarios. • ToE in river flows can precede ToE in precipitation by up to 50 years. • ToE substantially delayed or avoided in a low emissions pathway (SSP1-2.6). Climate change impacts on river flows are leading to substantial changes in water availability for human and natural systems. The significance of these impacts largely depends on the degree of change relative to natural variability. The 'Time of Emergence' (ToE) is the point in time (past or future) when the signal of climate change emerges from the noise of background variability. The ToE has been assessed for some climate variables but rarely streamflows. Here we investigate ToE of changes in streamflow across Australia for various characteristic periods relevant to different water management objectives. We assess the uncertainty in ToE estimates from different emissions pathways and a large ensemble of CMIP6 climate model projections. ToE is likely to occur earlier in hydrologic systems subject to low natural variability than those subject to high variability, and to systems that are vulnerable to failure over longer rather than shorter periods. There are clear regional differences in the patterns of ToE, with changes first emerging in south-west regions of Australia, followed by the south-east, then east and north. We estimate that ToE has already occurred in over 10% of sampled rivers for longer characteristic periods, primarily in south-west Australia. Importantly for planning, the results show that ToE in flows precedes ToE in precipitation by up to 50 years due to compounding effects of changes in annual precipitation, precipitation seasonality, and increasing temperatures. The number of catchments projected to have reached ToE by 2080 is heavily influenced by the trajectory of future emissions. A low emissions pathway generally consistent with aspirational goals of the Paris Climate Agreement (SSP1-2.6) substantially delays the emergence of significant hydrological change by up to 50 years, or negates emergence entirely by 2080, depending on location. Our methods can be applied to catchments globally, and our findings have implications for the prioritisation of climate adaptation efforts across different river systems and the urgency of continued action on climate change mitigation. [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]

Sequestering atmospheric carbon in soils is considered a key climate change mitigation strategy and including cover crops into cropping systems is commonly promoted as a management change that can increase soil organic carbon (SOC). Projecting SOC changes under climate change when cover crops are integrated into a cropping system is important because climate is a key driver of SOC dynamics and projected changes in climate are uncertain. Further, projecting SOC changes can provide landholders with information on the risk associated with the use of cover crops to generate carbon credits considering the inherent uncertainty in SOC changes under a changing climate. The Agricultural Production SIMulator was used to simulate SOC and yields of a typical crop rotation, with and without a cow pea cover crop, at 204 sites in the Riverina region of Southern Australia. Sowing cover crops reduced crop yields and increased SOC relative to the crop rotation without cover crops. GHG emissions associated with indirect land use change due to reduced crop yields and N 2 O emissions from the cover crop meant that sowing cover crops was unlikely to provide climate change mitigation. The number of carbon credits generated by participating in the soil carbon method of the Australian government's emissions reduction program varied greatly across the region with some sites not generating any credits. The implications of these results are discussed with respect to climate change mitigation and the risk of entering a SOC trading program when costs of compliance are high and the ability to generate carbon credits is uncertain. • Cover crops replace traditional fallow periods in dryland cropping systems. • Cowpea cover crops reduced the yield of cereal, oilseed and legume crops. • Total GHG emissions were generally greater than SOC sequestration. • Replacing fallows with cowpeas unlikely to reduce GHG emissions. • Climate change mitigation was variable across the region of interest. [ABSTRACT FROM AUTHOR]

This paper presents an integrated analysis of the costs and benefits of carefully constructed scenarios for the electrification of transport in Australia. Scenarios were constructed to responsively meet increased electricity demand, whilst maximising emission reduction, household finances and public health benefits. The scenarios bundle several technologies, including charging infrastructure, electric vehicles, home battery systems, and renewable energy. The fastest, mission-style, adoption scenario can reduce emissions by 9% of the 2030 carbon budget and reduce the loss of life by 24,000 by 2042. In all scenarios, government expenditure is dwarfed by the estimated public benefits, and households are nearly always better off in the medium to long term. Demonstrating the feasibility and advantages of surface transportation electrification in Australia, which presents cross-sections of rural and urban infrastructure, traffic and a large, socially and politically diverse population, provides broadly applicable evidence of the feasibility of electrification in other jurisdictions. [ABSTRACT FROM AUTHOR]

Cities must transform in order to address the challenge of climate change and to achieve societal ambitions such as the sustainable development goals. However, a key impediment to achieving transformation is underdeveloped understandings of how key actors and sectors within the built environment work together to achieve goals. This paper addresses these gaps by developing and visually presenting a process map to describe: the key processes involved in producing the built environment across its life stages; key sectors of the built environment, their key actors, and the activities coordinated between them. The process map was peer reviewed by an expert reference group of built environment professionals active in Australia and the UK. The motivation for developing this process map is to facilitate future research to identify and expedite opportunities for coordinated action to address significant societal challenges such as climate change action, and the sustainable development goals – which require transformative action in cities. • Cities must transform to address climate change • We develop a process map to describe the production of the built environment • Process map describes fundamental activities for producing the built environment • Process map spans built environment life stages; identifying activities and interactions of key sectors and actors • Can be applied to inform transformative action targeted at challenges such as climate change [ABSTRACT FROM AUTHOR]

Agricultural vulnerability assessment is a comprehensive and powerful analytical tool to locate hotspots with states of susceptibility to harm and powerlessness of agricultural system. It plays an important role in guiding policy makers to plan and implement adaptation practices to mitigate potential climate risks to crop. However, due to the diversity in the methodology of vulnerability assessment, there are still knowledge gaps in assessing and comparing crop vulnerability to climate in different regions of the world, including Australia. Our main objectives were to: (1) present a vulnerability analytical method for wheat yield, which can be applied to different areas where long-term crop yield and climate data are available. (2) quantify temporal changes of the vulnerability of wheat yield to historical climate. (3) identify the most vulnerable region in study area to provide guidance for climate mitigation. Our study developed an indicator-based method using exposure, sensitivity, and adaptive capacity to assess the vulnerability of crop yield. We used the long-term recorded wheat yield data, combining with comprehensive exposure index to assess climate vulnerability of historical yield with a case study area of south-eastern Australia's wheat belt. The results showed that from the 1930s to the 1990s, both climate exposure and sensitivity had large inter-annual variations with no significant trends detected. However, adaptive capacity increased by 34% from 1930s to 1950s, 54% from 1950s to 1970s, and 54% from 1970s to 1990s. By contrast, climate vulnerability across the wheat belt decreased by 13% from 1930s to 1950s, 15% from 1950s to 1970s, and 33% from 1970s to 1990s. This is mainly due to increased adaptive capacity with the improvement of agronomic management practices, technological and socio-economic progress. We identified the areas with the highest vulnerability were in the northwestern parts of wheat belt while the least vulnerable areas located in the southeast. We expect that these identified vulnerable hotspots can be used by different landholders to allocate natural resources and policymakers to plan the priority mitigation to adapt to climate change in the local scale. Moreover, the method of vulnerability assessment used in this study can be applied to other regions around the world where long-term crop yield and climate data are available. [Display omitted] • A modified indicator-based method was developed to assess wheat yield vulnerability. • Machine learning was used to obtain weights of climate indices when calculating exposure. • Historical vulnerability of wheat yield decreased as the improved adaptive capacity. • The most vulnerable areas were the north-western parts of the wheat belt. • This vulnerability assessment method can be applied to other regions with long-term data of crop yield and climate. [ABSTRACT FROM AUTHOR]

• MLR and RF were used to estimate current SOC stocks in south-eastern Australia. • Rainfall and minimum temperature were major drivers in determining SOC stocks. • The multi-GCM ensemble means suggested an overall decrease in SOC stocks. • The largest mean decrease of SOC stocks occurs in the high-rainfall alpine regions. Soil organic carbon (SOC) plays a key role in the sequestration of carbon that could otherwise be warming the atmosphere. Climate change including increased temperature and changed rainfall will greatly impact the global SOC cycle. There are still significant gaps in our knowledge of the size of the global SOC pool and how future climate will affect SOC stocks and flows in many parts of the world, including Australia. In this study, we used SOC data in a Digital Soil Mapping framework to predict current and future SOC stocks across the state of New South Wales (NSW) in south-eastern Australia. In the first phase of the study we estimated the current SOC stock using multiple linear regression (MLR) and random forest (RF) modelling, and in the second phase we projected the change of SOC stocks in the near future (2050s) and far future (2090s) under two Shared Socio-economic Pathways (SSPs) scenarios based on 25 global climate models (GCMs) from the Coupled Model Inter-comparison Project Phase 6 (CMIP6). Our spatial modelling showed that estimated current SOC stocks in NSW decreased from east to west. Multi-GCM ensemble means suggested SOC stocks would decrease by 7.6–12.9% under SSP2-4.5 and 9.1–20.9% under SSP5-8.5 across NSW under future climate. The extent of change in SOC stocks varied spatially with the largest mean decrease of SOC stocks occurring in the North Coast and South East (alpine) regions of NSW. Our findings can support decision-making in land management and climate change mitigation strategies in NSW at the regional level. Furthermore, the modelling methods can be applied to other areas where edaphic and landscape properties, land use, and climate data are available. [ABSTRACT FROM AUTHOR]