Maximising climate mitigation potential by carbon and radiative agricultural land management with cover crops

To reach the Paris climate targets, the mitigation capacity needs to be maximized across all components of the Earth system, especially land. Mitigation actions through land management, such as cover crops in agricultural soils, are often evaluated in terms of their carbon sequestration potential, while radiative forcing related to surface albedo changes is often ignored. The aim of this study was to assess the mitigation potential of cover crops, both as changes in biogenic greenhouse gas fluxes (CO2 and N2O) and albedo-driven radiative forcing at the top of the atmosphere (TOA). To achieve this, we have integrated a biogeochemistry model framework running on approximately 8000 locations across the European Union with detailed soil data, supplemented with time series of albedo measurements derived from satellite remote sensing. We found that carbon sequestration remained the dominant mitigation effect, with 1th and 3rd interquartile of 5.2–17.0 Mg CO2e ha−1 at 2050, and negligible changes in N2O emissions over that time-horizon. Cover crops were generally brighter than bare soils, hence, the reflected shortwave radiation at TOA ranged between 0.08–0.22 Wm−2 on average, broadly equivalent to a removal of 0.8–3.9 Mg CO2e ha−1. Through scenarios analysis, we further showed how the mitigation potential could be substantially increased by growing a high albedo chlorophyll-deficient cover crop. This radiative land management option has an additional benefit of providing its mitigation effect more rapidly than carbon sequestration, although additional studies might be warranted to evaluate local and non-local associated climatic effects, such as changes in patterns of surface temperature and precipitation.