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Research article

Soil carbon farming has the potential to bridge the global emissions gap

Authors
  • Jacqueline McGlade orcid logo (university college london)
  • downforce technologies (downforce technologies)

This article is a preprint currently under revision.

Abstract

There is growing interest globally in soil health and the role that enhanced soil organic carbon (SOC) can play in climate change mitigation, resilience, and food security. Different initiatives for SOC sequestration (SCS), such as Project Drawdown, ‘4p1000’ and RECSOIL have been proposed yet SCS commitments and targets are missing from the Nationally Determined Contributions (NDCs) to the 2015 Paris Agreement and the UNFCCC Global Stocktake. This paper asks whether a single, locally relevant target could be developed for SCS that would encourage widespread adoption of soil carbon removals practices by farmers and land managers globally? We used 210,00 local soils profiles from the World Soil Information System to assess the SOC potential of 2,352 million ha of agricultural land, identified with the Landsat Global Land Cover classification. Based on the local characteristics of the carbon sequestration capacity of soils, we found that a one percent average increase in SOC storage in croplands, pasture and irrigated fields would have the potential to sequester 84.9 GtC or 311 311 GtCO2-e [range 159 – 447 GtCO2-e]. This represents more than a decade of the emission reductions needed to have a chance of remaining on a 2°C or 1.5°C or Net Zero pathway. We argue that a one per cent target is easy to communicate and understand, especially as most farmers and land managers who regularly test their soils are familiar with the soil carbon percentages of their land.

Keywords: Soil Carbon Sequestration (SCS), Soil properties, Soil carbon storage potential, Carbon farming, Land classification, NDC, Emissions gap, Net Zero pathway, Climate, Policy and law, Sustainable development

Preprint Under Review
License
Creative Commons Attribution 4.0

 Open peer review from Pete Smith

Review
McGlade and Morris present a simple study where they take a global land cover and soil carbon data and arbitrarily increase the SOC stock in cropland and pasture-land by 1%. Unsurprisingly, they arrive at a very big number – 89GtC. Sanderman et al. (2017) – who the authors do not cite – showed that the total soil C lost from all land use change over the last 12,000 years is 133 GtC, so this suggestion that we might restore 89GtC on just cropland and pasture-land is wildly over-optimistic. On top of this, soil carbon in grassland (unless very degraded) tends to be high, with less potential to store additional carbon – so the idea that this can be increased by 1% is debatable. It should be noted that the 4p1000 initiative (which aims of 0.4% increase in SOC each year) has been criticised for being too optimistic – so it is not clear how this 1% increase in soil carbon is justified. In my opinion, there is potential, albeit limited, to increase soil organic carbon stocks in cropland soils, but overselling the potential for soil C sequestration in this way is irresponsible and dangerous. Despite declaring in their conflict of interest statement: “The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper”, the authors are affiliated to a company that stands to profit from convincing farmers / policy-makers that soil carbon sequestration can bridge the emissions gap. It cannot, and this arbitrary calculation adds little to the evidence base.

Note:
This review refers to round 1 of peer review.

 Open peer review from Jules Pretty

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-AG.AOSFKU.v1.RBSGGD
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Earth & Environmental sciences , Agriculture , Geosciences
Keywords: Land classification , NDC , Net Zero pathway , Carbon farming , Soil carbon storage potential , Policy and law , Soil properties , Climate , Emissions gap , Sustainable development , Soil Carbon Sequestration (SCS)

Review text

This is an important, timely and clearly-written paper on the value and potential for soil carbon sequestration to contribute to climate mitigation. It is clear that absolute emissions reductions will be essential for the global transition to net zero. The UNFPCC's Race to Zero project mandates 80% of net zero achievements must be emissions cuts. The remain 20% (of the current 56 Gt of carbon dioxide equivalent) can come from long-term carbon capture. The authors have shown how more sustainable forms of agriculture are already locking up carbon below and above-ground. This paper summarises mechanisms, and provides authoritative quantitative analysis. The findings here are relevant and communicable to and for farmers, as well as researchers and policy makers.

I have no hesitation in recommending this paper for publication in UCL Open Environment. It meets all the essential criteria



Note:
This review refers to round 1 of peer review.