Abstract
To limit warming to well below 2°C, most scenario projections rely on greenhouse gas removal technologies (GGRTs); one such GGRT uses soil carbon sequestration (SCS) in agricultural land. In addition to their role in mitigating climate change, SCS practices play a role in delivering agroecosystem resilience, climate change adaptability and food security. Environmental heterogeneity and differences in agricultural practices challenge the practical implementation of SCS, and our analysis addresses the associated knowledge gap. Previous assessments have focused on global potentials, but there is a need among policymakers to operationalise SCS. Here, we assess a range of practices already proposed to deliver SCS, and distil these into a subset of specific measures. We provide a multidisciplinary summary of the barriers and potential incentives towards practical implementation of these measures. First, we identify specific practices with potential for both a positive impact on SCS at farm level and an uptake rate compatible with global impact. These focus on: (a) optimising crop primary productivity (e.g. nutrient optimisation, pH management, irrigation); (b) reducing soil disturbance and managing soil physical properties (e.g. improved rotations, minimum till); (c) minimising deliberate removal of C or lateral transport via erosion processes (e.g. support measures, bare fallow reduction); (d) addition of C produced outside the system (e.g. organic manure amendments, biochar addition); (e) provision of additional C inputs within the cropping system (e.g. agroforestry, cover cropping). We then consider economic and non‐cost barriers and incentives for land managers implementing these measures, along with the potential externalised impacts of implementation. This offers a framework and reference point for holistic assessment of the impacts of SCS. Finally, we summarise and discuss the ability of extant scientific approaches to quantify the technical potential and externalities of SCS measures, and the barriers and incentives to their implementation in global agricultural systems.
Highlights
Despite concerted international effort to curb greenhouse gas (GHG) emissions, their release to the atmosphere accelerated throughout the first decade of the 21st century (Le Quéré et al, 2012)
This as‐ sessment has identified a range of soil carbon sequestration (SCS) practices which can be con‐ sidered to be an effective route to greenhouse gas removal (GGR) in global agricultural soils, and to critically assess the biophysical, economic and social impacts of these measures and their implementation in global systems
While not unique in this respect (e.g. Chenu et al, 2019), in providing a framework for the application of existing knowledge and method‐ ologies to the challenge of local‐ and regional‐scale SCS implemen‐ tation, this assessment represents a novel approach in facilitating SCS
Summary
Despite concerted international effort to curb greenhouse gas (GHG) emissions, their release to the atmosphere accelerated throughout the first decade of the 21st century (Le Quéré et al, 2012). While lat‐ eral transport of C reduces only local stocks by definition, improving local soil C storage in this way may provide increased availability of labile C fractions, the mineralisation of which provides nutrients for plant growth (Chenu et al, 2019); as such, these measures may indirectly increase SOC inputs via increased primary productivity.
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