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Soil-based carbon farming has been identified in previous research as a win-win for farm productivity and the mitigation of climate change through carbon sequestration. However, it faces numerous barriers to adoption, including low carbon prices, high transaction costs, information barriers and high uncertainty around future outcomes, markets and policy conditions. Collaboration between landholders and other stakeholders has been proposed as a potential means of overcoming some of these barriers, while maximising the benefits of soil-based carbon farming. In this article, we present the results of a two-stage process investigating collaborative soil-based carbon farming in Australia, involving national-scale key informant interviews and a regional-scale Participatory Rural Appraisal. Fifty-three interviews were undertaken with key carbon farming stakeholders, including landholders, landholder groups, carbon service providers, government, researchers and the financial sector. Collaboration was seen to offer the greatest advantages in relation to knowledge-sharing and social support, followed by its potential to increase carbon income through enhanced bargaining power and the optimisation of co-benefits. The advantages of collaboration were less clear in relation to reducing costs or maximising farm productivity and collaboration also presents new challenges around risk and complexity. Under current conditions, informal collaboration models were seen to offer the best balance between the benefits and risks, with existing cooperatives also well-placed to diversify into carbon. Alternative conditions in the future or in other locations would be needed to facilitate models involving joint projects, pooled credits, shared land management and/or the creation of new carbon-specific cooperatives. • Soil-based carbon farming benefits both carbon sequestration and farm productivity. • Advantages of collaboration are greatest for knowledge-sharing and social support. • Collaboration less beneficial in relation to cost-reduction and farm productivity. • Informal models for collaboration preferred by study participants. • Existing agricultural cooperatives are well-placed to diversify into carbon farming. [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]