Challenging claimed benefits of soil carbon sequestration for mitigating climate change and increasing crop yields: heresy or sober realism?

There is overwhelming evidence that increasing the organic carbon (C) content of cropland soil improves its physical, chemical and biological properties, with benefits for the growth of crop roots and the functioning of soils in the wider environment (King et al., 2020; Kopittke et al., 2022; Lal 2020). This is entirely uncontroversial. It is currently relevant because there is evidence that soil organic carbon (SOC) in many cropland soils globally is declining (Sanderman et al., 2017) and is vulnerable to further loss from climate change (Lugato et al., 2021). It may, therefore, seem counterintuitive, and even heretical or downright unhelpful, for a paper to challenge two widely stated claims connected with SOC as is done in the paper entitled “Carbon for soils, not soils for carbon” by Moinet et al. (2023). The two claims challenged by the authors are: 1. Sequestration of C in agricultural soils can make a substantial contribution to climate change mitigation. 2. Increasing SOC will routinely lead to increased crop yields and contribute to global food security. The authors are particularly critical of these two assertions being combined to make the claim that SOC sequestration is a “win-win” strategy. They point out that climate change and food security have both been described as “wicked problems” of “daunting complexity” so blanket solutions that claim to solve both “should prompt some degree of scepticism.”