Eric Verrecchia (Honorary Professor at the Institute of Earth Surface Dynamics at the Faculty of Geosciences and Environment of Lausanne)
Imagine buying a house without verifying the foundations. That’s essentially what agricultural “carbon credits” offer. The principle sounds appealing: a farmer adopts better practices, their soil stores more organic carbon, and emitting companies buy “credits” from them to offset their CO2 emissions. A recent scientific study* scrutinized the ten major international protocols used to calculate these credits. The outcome: it reached an alarming result. Some protocols don’t even bother to measure the organic carbon content in the soil initially, preferring to use regional average values. As a result, errors can reach a factor of 2.5 before even evaluating anything. Others simply ignore recognized agricultural practices that impact soil organic carbon, such as cover crops or crop rotation diversity. In short: values are credited that no one has really measured.
And what happens when the protocol actually relies on a field approach to verify that organic carbon is well buried? Not surprisingly, the situation isn’t much brighter. The methods used, the tools, the depth of extraction, the number of samples taken, all vary from one protocol to another, sometimes in proportions that significantly skew the results. And as if these failures weren’t enough, the details of these measurements are often kept secret, making any independent verification impossible. Meanwhile, companies that buy these credits, often at a high cost, then emit with the clear conscience of those who believe they have paid their debt. This study doesn’t argue that the idea of agricultural carbon credits is inherently bad; encouraging organic carbon storage in soils is a relevant practice not only from a “climate” perspective. But it warns: without common, rigorous, and transparent, scientifically based rules, these credits often amount today to empty promises. In conclusion, thanks to this type of study, one can only once again observe the extent of the mismatch between the apparent sophistication of these carbon markets and the scientific fragility that underpins them. But does this observation really remain an isolated case in climate policies proposed?
* 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.
