The Significance of the Erosion-induced Terrestrial Carbon Sink

TLDR

Estimating carbon balance in erosional and depositional landscapes is complicated by soil redistribution affecting net primary productivity and decomposition, and studies disagree on whether erosion constitutes a carbon sink. The study aims to clarify the conceptual basis for erosion acting as a carbon sink. An erosional carbon sink exists when dynamic replacement of eroded carbon and reduced decomposition at deposition sites together outweigh erosional losses. The criterion is met in many settings, with erosion and deposition providing a net positive carbon sequestration that offsets up to 10 % of global fossil‑fuel CO₂ emissions in 2005, exemplified by 1 % of NPP and 16 % of eroded carbon in Mississippi and California watersheds.

Abstract

Estimating carbon (C) balance in erosional and depositional landscapes is complicated by the effects of soil redistribution on both net primary productivity (NPP) and decomposition. Recent studies are contradictory as to whether soil erosion does or does not constitute a C sink. Here we clarify the conceptual basis for how erosion can constitute a C sink. Specifically, the criterion for an erosional C sink is that dynamic replacement of eroded C, and reduced decomposition rates in depositional sites, must together more than compensate for erosional losses. This criterion is in fact met in many erosional settings, and thus erosion and deposition can make a net positive contribution to C sequestration. We show that, in a cultivated Mississippi watershed and a coastal California watershed, the magnitude of the erosion-induced C sink is likely to be on the order of 1% of NPP and 16% of eroded C. Although soil erosion has serious environmental impacts, the annual erosion-induced C sink offsets up to 10% of the global fossil fuel emissions of carbon dioxide for 2005.