The soil carbon erosion paradox reconciled

Abstract. The acceleration of erosion, transport and burial of soil organic carbon (C) in response to agricultural expansion represents a significant perturbation of the terrestrial C cycle. Recent model advances now enable improved representation of the relationships between sedimentary processes and C cycling and this has led to substantially revised assessments of changes in land C as a result of land cover and climate change. However, surprisingly a consensus on both the direction and magnitude of the erosion-induced land-atmosphere C exchange is still lacking. Here, we show that the apparent soil C erosion paradox, i.e., whether agricultural erosion results in a C sink or source, can be reconciled when comprehensively considering the range of temporal (from seconds to millennia) and spatial scales (from soil microaggregates to the Land Ocean Aquatic Continuum (LOAC)) at which erosional effects on the C cycle operate. Based on the currently available data (74 studies), we developed a framework that describes erosion-induced C sink and source terms across scales. Based on this framework, we conclude that erosion is a source for atmospheric CO₂ when considering only small temporal and spatial scales, while both sinks and sources appear when multi-scaled approaches are used. We emphasize the need for erosion control for the benefits it brings for the delivery of ecosystem services, particularly in low-input systems, but our analysis clearly demonstrates that cross-scale approaches are essential to accurately represent erosion effects on the global C cycle.