Preservation of Soil Organic Carbon (SOC) through Ecosystems’ Soil Retention Services in China

Soil erosion exerts a profound impact on the stocks of soil organic carbon (SOC), disrupting the carbon cycle and contributing to global warming. Through its role in mitigating soil erosion, the soil retention service of ecosystems holds the potential to stabilize and safeguard the SOC reservoir. This facet has yet to be comprehensively investigated. In this study, we quantified the preservation of SOC resulting from soil retention services in China, achieved by estimating both actual SOC erosion and potential SOC erosion using the Universal Soil Loss Equation (USLE). We find that (1) annually, SOC erosion in China amounted to 0.10 Pg C, primarily concentrated in croplands (47.8%), grasslands (21.2%), and barren lands (15.7%). Noteworthy hotspots emerged within the Soil and Water Conservation Divisions (SWCD) of key regions like the Tibetan Plateau (TP), the southwestern purple soil region (SW), and the karst region (KT). (2) The soil retention service curtailed the loss of a substantial 4.18 Pg C of SOC per year, predominantly attributed to forest ecosystems (66.1%). Hotspots of this preservation were clustered in the SWCD of the southern red soil region (SR), KT, and TP. These outcomes highlighted the critical role of soil retention services in preventing considerable carbon losses from terrestrial ecosystems. It significantly contributes to climate change mitigation and warrants recognition as an important nature-based solution in the pursuit of carbon neutrality. Forest ecosystems emerge as paramount in SOC preservation, which will be further improved with forest restoration. Beyond addressing soil erosion, future endeavors in soil and water conservation must equally address SOC erosion to comprehensively tackle carbon loss concerns.