Soil carbon sequestration in grazing systems: managing expectations

Godde, Cécile M. [Commonwealth Scientific and Industrial Research Organisation, The University of Queensland, St Lucia, Australia] de Boer, Imke J. M. [Animal Production Systems group, Wageningen University & Research, Wageningen, The Netherlands] Zu Ermgassen, Erasmus [UCL] Herrero, Mario [Commonwealth Scientific and Industrial Research Organisation, St Lucia, Australia] van Middelaar, Corina E. [Animal Production Systems group, Wageningen University & Research, Wageningen, The Netherlands] Muller, Adrian [Department of Socioeconomics, Research Institute of Organic Agriculture FiBL, Frick, Switzerland] Röös, Elin [Department of Energy and Technology and Centre of Organic Production and Consumption (EPOK), Swedish University of Agricultural Sciences, Uppsala, Sweden] Schader, Christian [Department of Socioeconomics, Research Institute of Organic Agriculture FiBL, Frick, Switzerland] Smith, Pete [Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK] van Zanten, Hannah H. E. [Animal Production Systems group, Wageningen University & Research, Wageningen, The Netherlands] Garnett, Tara [Food Climate Research Network, Environmental Change Institute and the Oxford Martin School, University of Oxford, Oxford, UK] et al.[show all]

Grazing systems emit greenhouse gases, which can, under specific agro-ecological conditions, be partly or entirely offset by soil carbon sequestration. However, any sequestration is time-limited, reversible, and at a global level outweighed by emissions from grazing systems. Thus, grazing systems are globally a net contributor to climate change and the time scale of key processes needs to be factored into any mitigation efforts. Failing to do so leads to unrealistic expectations of soil carbon management in grazing systems as a mitigation strategy. Protecting the large carbon stocks in grazing lands is also essential in order to avoid further climate change from additional CO2 release. Despite the time-limited and reversible nature of soil carbon sequestration in grazing lands, sequestration should be promoted in cases where it delivers environmental and agronomic benefits as well as for its potential, particularly on degraded land, to increase the feasibility of limiting global warming to less than 2 or preferably 1.5 °C. Some peer-reviewed sequestration estimates are of a similar order of magnitude to other food systems mitigation options over a 10– 20 years period, such as reducing food loss and waste by 15% or aligning diets with current health related dietary-recommendations. However, caution should be applied to such comparisons since mitigation estimates are associated with large uncertainties and will ultimately depend on the economic cost-benefit relation, feasibility of implementation and time frame considered.