Reappraisal of the place of cultivated plants in the carbon budget

Abstract

The impact of agriculture on the climate remains underestimated due to the systematic exclusion of annual crops from carbon budgets. Considered too ephemeral, these crops are nevertheless responsible for the absorption and storage of approximately one-third of the carbon biofixed by photosynthesis, with half-lives that are not limited to a single season but extend on average over 8.9 years. The kinetics of variation in carbon capture and release by cultivated plants over the half-century were simulated to complete the probabilistic calculation of the carbon budget components. In 2023, all cultivated plants (crops, grasslands, and forest plantations) had a stored carbon half-life of 17.6 years. They had removed 39.2+-0.5 billion tonnes of CO2 (GtCO2) per year from the atmosphere, more than global emissions from hydrocarbon combustion. The time distribution allowed by this simulation suggests that cultivated plants would have biofixed a cumulative net total of 455 GtCO2 in 2023, or 14% of the mass of atmospheric CO2. Given the importance of this anthropogenic carbon capture and storage by cultivated plants, both in duration and quantity, rural activities should be integrated into carbon budgets and the resulting climate strategies, and recognized as a carbon capture and storage (CCS) device in carbon cycle regulation policies. This recognition would allow for the fair valuation of the work of farmers and foresters as part of the ecological transition, particularly through remuneration mechanisms such as carbon credits.