Biogenic carbon is part of the natural carbon cycle, meaning that its sequestration is potentially reversible, as stored carbon can be released back into the atmosphere. This raises important questions about the long-term climate benefits of carbon farming practices and calls for assessment approaches that account for the duration of carbon storage. Moreover, changes in other greenhouse gas emissions and additional effects on the Earth’s energy balance can also influence the overall climate impact of a given agricultural practice.
A new MARVIC report, now publicly available here, addresses these challenges by examining how the climate impacts of carbon farming practices evolve over time. The document, titled “Radiative Forcing of Carbon Farming practices: Insights into climate impacts of non-permanence, greenhouse gas trade-offs, and biogeophysical effects”, was developed by Flora Desmet and Jens Leifeld (Agroscope), with contributions from other MARVIC partners. Using climate modelling approaches, the researchers assessed the effects of different practices over short, medium and long time horizons.
The findings show that temporary soil carbon sequestration provides climate benefits, although these can decrease substantially compared with permanent storage over longer time horizons. The report also highlights how changes in nitrous oxide (N2O) and/or methane (CH4) emissions can influence the overall mitigation potential of practices such as crop residue management and peatland rewetting. Additionally, it examines the importance of biogeophysical effects, particularly changes in surface albedo, which are often overlooked in carbon farming assessments.
These results highlight the importance of considering the duration and timing of climate impacts when evaluating carbon farming projects. They provide valuable insights for improving Monitoring, Reporting and Verification (MRV) methodologies and informing the development of credible carbon farming certification schemes. The findings have also informed a MARVIC policy brief, which provides recommendations on the permanence of soil carbon removals and their use in greenhouse gas emissions compensation.
