Tensions between private and public benefit associated with carbon farming

Theory posits that land use sustainability could be improved through implementation of management regimes that balance land manager aspirations on the one hand with those of society on the other. Here, our aim was to contrast private and public benefits realised from grazing management approaches aimed at either maximising farm enterprise profit or soil organic carbon (SOC) accrual. When grazing management was conducted with the aim of maximising profit, a fast rotation, high stocking rate regime was optimal; enterprise profit was $AU55/ha/year higher than optimal management approaches for maximising SOC accrual. In contrast, flexible grazing management (with varying duration based on leaf stage and biomass availability) tended maximise SOC accrual, with 0.4 t/ha/year more SOC accrual than the continuous grazing treatment. As concurrent adoption of multiple farm management regimes better reflect real-world practicalities, we also examined how optimal farm management differed when one or two grazing approaches were operationalised to maximise profit and SOC accrual simultaneously. Simultaneous adoption of multiple grazing treatments on farm elicited greater profit ($AU7/ha/year higher than when one management approach adopted across the whole farm), with the most preferable regime being a combination of fast rotation with high stocking rate and flexible grazing. Effects of carbon price and farm size were more influential on production and profit compared with weather variability, even though the latter altered the trajectory of seasonal SOC accrual. For carbon prices of $AU31/t CO₂-e, flexible and high intensity fast rotational grazing were each adopted on around half of farm area; as carbon prices increased to $AU50/t CO₂-e, flexible grazing management across the entire farm resulted in the greatest profit and SOC (additional 0.21 t SOC/ha/year under the flexible grazing treatment cf. continuous grazing). Our results demonstrate that private land management is heavily influenced by market prices, reflecting the relative economic balance between commodity prices, such as livestock and crops, and resource prices, such as carbon, biodiversity and water. We contend that carbon prices would need to increase significantly to alter land management and carbon removals at scale.