Soil erosion is unlikely to drive a future carbon sink in Europe

Abstract

Understanding of the processes governing soil organic carbon turnover is confounded by the fact that C feedbacks driven by soil erosion have not yet been fully explored at large scale.However, in a changing climate, variation in rainfall erosivity (and hence soil erosion)maychange the amount of Cdisplacement, hence inducing feedbacks onto the land C cycle.Using a consistent biogeochemistry-erosionmodel framework to quantify the impact of future climate on the C cycle, we show that C input increases were offset by higher heterotrophic respiration under climate change. Taking into account all the additional feedbacks and C fluxes due to displacement by erosion, we estimated a net source of 0.92 to 10.1 Tg C year-1 from agricultural soils in the European Union to the atmosphere over the period 2016-2100. These ranges represented a weaker and stronger C source compared to a simulation without erosion (1.8 Tg C year-1), respectively, and were dependent on the erosion-driven C loss parameterization, which is still very uncertain. However, when setting a baseline with current erosion rates, the accelerated erosion scenario resulted in 35%more eroded C, but its feedback on the C cycle wasmarginal. Our results challenge the idea that higher erosion driven by climate will lead to a C sink in the near future.