First Signs That National Cropland Organic Carbon Loss Is Reversing in British Topsoils

ABSTRACT

High rates of soil organic carbon (SOC) loss from cropland soils are well known, contributing to climate change and compromising soil and ecosystem health. Stabilising and reversing the loss of organic matter from cropland soils is a challenge for all nations to meet the United Nations Sustainable Development Goals. Sustainable land management (SLM) has been promoted as a mechanism of achieving this, but to date, there is no evidence of positive impacts at scale. Here we show the first signs of the reversal of soil carbon loss in cultivated topsoils in Great Britain, following a period of reported SLM uptake, using 40+ years of national soil monitoring from the UKCEH Countryside Survey. Following a prolonged historic decline at rates of ￢ﾈﾒ0.16￢ﾀﾉt￢ﾀﾉha ￢ﾈﾒ1 ￢ﾀﾉyear ￢ﾈﾒ1 , there was a significant increase in cropland topsoil SOC stocks (0￢ﾀﾓ15￢ﾀﾉcm) from 2007 to 2019￢ﾀﾓ22 with an accrual rate of 0.17￢ﾀﾉt￢ﾀﾉha ￢ﾈﾒ1 ￢ﾀﾉyear ￢ﾈﾒ1 , approximately 0.74￢ﾀﾉMtC￢ﾀﾉyear ￢ﾈﾒ1 nationally. We discuss reported management shifts in Great Britain in the corresponding period and identify a reduction in conventional tillage and reduced straw removal as potential drivers, but highlight additional evidence gaps worthy of consideration. This increase in topsoil SOC may represent net carbon sequestration or carbon redistribution (geographic or vertical) but nevertheless demonstrates that topsoil properties can be restored at scale and offers hope that a concerted effort by land managers can halt, and potentially reverse, SOC loss from cropland soils.