Greenhouse gas emissions from soils—A review

TLDR

Soils act as both sources and sinks of greenhouse gases, and accurate quantification of their emissions and storage is essential for reliable global budgets that inform land‑use management and climate research. This review examines soil emission processes and their controlling factors, surveys key studies across land‑cover types and climate zones, evaluates measurement systems, and highlights data gaps and a bias toward northern‑hemisphere observations. By compiling literature estimates of a conservative average emission rate of 300 mg CO₂e m⁻² h⁻¹, the authors extrapolate to global annual net soil emissions of at least 350 Pg CO₂e. These emissions represent roughly 21 % of the global soil carbon and nitrogen pools and are comparable to the 33.4 Pg CO₂ emitted annually by fossil fuels and cement production.

Abstract

Soils act as sources and sinks for greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Since both storage and emission capacities may be large, precise quantifications are needed to obtain reliable global budgets that are necessary for land-use management (agriculture, forestry), global change and for climate research. This paper discusses exclusively the soil emission-related processes and their influencing parameters. It reviews soil emission studies involving the most important land-cover types and climate zones and introduces important measuring systems for soil emissions. It addresses current shortcomings and the obvious bias towards northern hemispheric data. When using a conservative average of 300 mg CO2e m−2 h−1 (based on our literature review), this leads to global annual net soil emissions of ≥350 Pg CO2e (CO2e = CO2 equivalents = total effect of all GHG normalized to CO2). This corresponds to roughly 21% of the global soil C and N pools. For comparison, 33.4 Pg CO2 are being emitted annually by fossil fuel combustion and the cement industry.