Eric Verrecchia (Honorary Professor at the Institute of Earth Surface Dynamics at the Faculty of Geosciences and Environment in Lausanne)
Imagine buying a house without anyone checking the foundations. This is essentially what agricultural “carbon credits” propose. The principle seems appealing: a farmer adopts better practices, their soil stores more organic carbon, and CO2-emitting companies buy “credits” from them to offset their emissions. A recent scientific study* scrutinized the ten major international protocols used to calculate these credits. The result: it revealed a troubling outcome. Some protocols don’t even bother to measure the organic carbon present in the soil at the beginning, opting to use regional average values instead. As a result, the error can reach a factor of 2.5 before even evaluating anything. Others simply ignore agricultural practices known for their impact on soil organic carbon, such as cover crops or crop rotation diversity. In essence: credits are given based on values that haven’t been accurately measured.
And what happens when the protocol actually relies on a field approach to verify if the organic carbon is buried correctly? Unsurprisingly, the situation isn’t much better. The methods, tools, depth of assessment, number of samples taken – all of this varies from one protocol to another, sometimes to extents that significantly skew the results. And as if these shortcomings weren’t enough, the details of these measures often remain confidential, making independent verification impossible. Meanwhile, companies purchasing these credits, often at great cost, emit with the belief that they have paid off their debt. This study doesn’t argue that the idea of agricultural carbon credits is inherently bad; encouraging the storage of organic carbon in soils remains relevant, not just from a “climate” perspective. But it warns: without common, rigorous, and transparent, scientifically grounded rules, these credits often amount to empty promises today. In conclusion, thanks to this type of study, we can only once again observe the extent of the mismatch between the apparent sophistication of these carbon markets and the scientific fragility underlying them. But is this observation truly an isolated case from the climate policies implemented?
* Dupla, X., Bonvin, E., Deluz, C., Lugassy, L., Verrecchia, E., Baveye, P. C., Grand, S., & Boivin, P. (2024). Are soil carbon credits empty promises? Shortcomings of current soil carbon quantification methodologies and improvement avenues. Soil Use and Management, 40, e13092. https://doi.org/10.1111/sum.13092. The article is freely accessible.
