The potential for land sparing to offset greenhouse gas emissions from agriculture

In this paper, researchers from a number of UK and US research institutions explore the potential for land sparing as a greenhouse gas (GHG) offsetting strategy – that is, by increasing crop and livestock yields so as to enable agricultural land to be freed up and used for habitat restoration (for example) an enable carbon sequestration. 

The researchers first identified the upper and lower bounds of the technical potential for crop and livestock yield increases (for discussion of how these yield projections were obtained and their feasibility, see the Supplementary information, here).  They then predicted the UK’s agricultural emissions for 2050. This included emissions arising from agricultural energy use (often not included in agricultural accounting), as well as overseas emissions associated with imports to the UK; imports that are predicted to become necessary where the UK’s own agricultural capacity is out-stripped by demand. Next they formulated a land-use strategy that included active restoration of habitats (restoration of wet peatland on spared organic soils and growth of native broadleaved forest). 

By combining this land-use strategy with their upper and lower bound yield projections, they were able to make predictions of net 2050 emissions relative to 1990 levels, and thereby assess the effectiveness of land-sparing as a strategy by itself.  Finally, they assessed the impact of demand-side measures (reduced, that Is halved, meat consumption and food waste) implemented alongside land-sparing, as well as the impact of alternative uses of spared land, such as growing bioenergy crops.

The main findings of the paper are:

  • land-sparing offers significant potential to mitigate net GHG emissions (up to 80% reduction in emissions relative to 1990 baseline), with upper-bound yield projections leading to decreased farming emissions, primarily through more efficient livestock production, and increased carbon sequestration by actively restored habitats;
  • combining measures has significant benefits (e.g. land-sparing from moderate yield growth combined with meat reduction has potential to reduce emissions by more than 80%); the mitigation potential of bioenergy alternatives to land-sparing are low.

The figure below, copied from the paper shows that carbon sequestration gains from habitat restoration accounts for the bulk of the GHG mitigation effects (dark shading on the bars).  Direct on- farm reductions (from use of more efficient crops or livestock breeds for example) – see light shading on the bars - account for a far smaller percentage of the overall mitigation potential.

Note this comment too, copied from the paper on the mitigation potential of bioenergy production – one of the alternative land use options they modelled: “Our results suggest that the mitigation potential of oilseed rape for biodiesel is negligible, and the potential of Miscanthus and short- rotation coppice depends strongly on the fossil fuel being displaced, outperforming natural regeneration only if displacing coal.”

The authors urge caution in the interpretation of their results, noting that the upper bound of technical potential for yield increases that they have identified is unlikely to be achievable in practice, owing to political, economic and social factors; nor are the projected benefits necessarily sustainable in the long term.

Abstract

Greenhouse gas emissions from global agriculture are increasing at around 1% per annum, yet substantial cuts in emissions are needed across all sectors. The challenge of reducing agricultural emissions is particularly acute, because the reductions achievable by changing farming practices are limited and are hampered by rapidly rising food demand. Here we assess the technical mitigation potential offered by land sparing—increasing agricultural yields, reducing farmland area and actively restoring natural habitats on the land spared. Restored habitats can sequester carbon and can offset emissions from agriculture. Using the UK as an example, we estimate net emissions in 2050 under a range of future agricultural scenarios. We find that a land-sparing strategy has the technical potential to achieve significant reductions in net emissions from agriculture and land-use change. Coupling land sparing with demand-side strategies to reduce meat consumption and food waste can further increase the technical mitigation potential—however, economic and implementation considerations might limit the degree to which this technical potential could be realized in practice.

Citation

Lamb, A., Green, R., Bateman, I., Broadmeadow, M., Bruce, T., Burney, J., Carey, P., Chadwick, D., Crane, E., Field, R., Goulding, K., Griffiths, H., Hastings, A., Kasoar, T., Kindred, D., Phalan, B., Pickett, J., Smith, P., Wall, E., zu Ermgassen, E.K.H.J., and Balmford, A. (2016). The Potential for Land Sparing to Offset Greenhouse Gas Emissions from Agriculture. Nature Climate Change [online], 1–5.

Read the full paper here and for further coverage, see this BBC article.

You can find related resources in the research Library categories on land-sparing vs. land-sharing, land use and land use change, ecosystems and ecosystem services, landscapes, climate change: mitigation, GHG impacts and mitigation, meat, eggs and alternativesfood waste.

See also this Science paper and this report, both about sustainable intensification, by the FCRN

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