Blog by Ellen Fay, co-founder and co-Executive Director,
Realising the potential of soil carbon sequestration for atmospheric greenhouse gas removal
As Professor of Soils & Global Change at the University of Aberdeen, who better than Professor Pete Smith to give the conference a clear and concise breakdown of the current possibilities and limitations of soil carbon sequestration in reducing atmospheric greenhouse gases. His findings simplify messaging about its role in climate change mitigation. He provided that clear balance between tempering optimistic expectations and addressing the challenges from more sceptical voices, while clarifying the reasons to be hopeful.
Pete outlined at the very beginning that in theory soils could sequester up to around 10% of current global greenhouse gas emissions. However, critically the contribution is conditional, time-limited, and highly dependent on sustained land management.
鈥淔or people getting carried away saying soil carbon is the panacea and going to solve all of our problems, it鈥檚 not. It is time limited and is reversible鈥
Soil carbon sequestration slows as soil approaches equilibrium, and any gains can be rapidly reversed if land management practices change, or soils become degraded. From a global GHG management perspective the message is clear: soil carbon sequestration cannot replace emissions reductions, but can be used alongside them, ideally to counter-balance any remaining emissions for the agricultural sector.
Measurement, reporting and verification (MRV) 鈥 the biggest barrier
A central focus of Pete鈥檚 presentation was measurement, reporting and verification (MRV), which emerged as the biggest barrier to scaling soil carbon sequestration. Pete explained that while direct soil measurements are accurate, they are also slow, destructive to soil structure, and expensive.
New measurement approaches including spectroscopy, gamma radiation, and satellite-based techniques, are under active development and show promise. However, they are not yet capable of reliably detecting small changes in soil carbon against large background stocks. So, claims that soil carbon can currently be measured accurately from space are simply not well supported by the evidence. These technologies may eventually reduce costs and improve coverage, but further development is needed.
The need for an integrated MRV framework
Throughout the presentation, Pete managed to weave in the limitations whilst simultaneously offering solutions. No single method, he argued, can provide a sufficient MRV system on its own. Instead, a robust and credible framework is needed, one that combines multiple sources of evidence and bring together:
- Long-term experiments that track soil carbon change over decades
- Short-term measurements that capture carbon and greenhouse gas fluxes
- Process-based soil and ecosystem models, calibrated with real data
- Spatial datasets on soils, land use, and climate
- Farm-level activity (management) data
- Remote sensing to verify practices and provide additional inputs
- Periodic soil resampling for independent validation
These elements already exist within the scientific community, but they are not yet fully integrated and are unevenly distributed globally. Significant data gaps remain, particularly in tropical and subtropical regions.
The Role and Limitations of Models and Farm Data
Pete emphasised the importance of models to project future soil carbon changes, so long as they are grounded in real-world observations and continuously validated.
Remote sensing, often used to validate management data and to provide inputs to soil carbon models can strengthen the overall MRV framework; however, Pete advised that it shouldn鈥檛 be used as a standalone solution. These tools can verify management practices and improve real-time model calibration, but it cannot directly measure soil carbon change.
One vast and underused source of direct soil carbon data lies at the farm level. As Pete explained, data already being collected by individual farms could be repurposed to inform soil carbon models without imposing additional administrative burdens on farmers. Provided it is used in a decentralised or anonymised system rather than a centralised public database, this resource could become one of the most valuable assets for improving soil carbon monitoring.
Scaling up and looking ahead
Rather than leaving the audience overwhelmed by the scale of the challenge, Pete highlighted international initiatives that show how these approaches can be implemented at scale.
The FAO鈥檚 RECSOIL programme, for example, illustrates how bottom-up, country-led systems can build capacity, integrate data and models, and support soil carbon accounting in both developed and developing regions. Together, these efforts suggest that wider implementation is achievable with relatively modest additional investment.
Furthermore, improving MRV through artificial intelligence, machine learning, robotics and advance data assimilation was presented as a significant opportunity to increase accuracy and efficiency if properly integrated.
Bringing these ideas together, Pete emphasised that soil carbon has the potential to act as a headline indicator of soil health, with strong links to productivity, resilience, ecosystem services, and broader sustainability goals. Yet this potential depends on robust, integrated, harmonised and credible MRV systems to track changes in soil carbon and meaningfully assess soil health. In this sense, soil carbon underpins soil health – but only careful measurement can unlock its full value.
