Cutting the climate impact of land use: methodology

April 2019
Caterina Brandmayr Caterina BrandmayrSenior policy analyst020 7630 4516cbrandmayr@green-alliance.org.uk
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This analysis estimates the emissions reduction and climate mitigation interventions required by 2030, for the UK to be on track to achieve a net zero greenhouse gas agriculture and related land use sector by 2040, building on analysis published by the Committee on Climate Change (CCC) and the Royal Society.[1]

Emissions from land use in 2030
The CCC’s analysis, published in November 2018, was taken as the starting point. Based on these findings, emissions from land use were 52.7MtCO2e per year in 2016, of which 41.7MtCO2e arise from agriculture, 18.5MtCO2e from peatlands and 5.8MtCO2e from settlements. The land use, land use change and forestry (LULUCF) sector sequesters 13.4MtCO2e.[2] Emissions from settlements were excluded from our analysis as we decided to focus on farming and related land uses only. Overall emissions were, therefore, 46.9MtCO2e per year in 2016.

To estimate the extent to which emissions need to be cut by 2030, to be on track for carbon neutrality[3] by 2040, we assume that net emissions reach zero by 2040, following a linear trajectory. This means that annual emissions from the land use sector (excluding settlements) should be 19.5MtCO2e per year in 2030.

Climate change mitigation action, beyond the CCC’s HBP scenario
Based on the CCC’s ‘high biomass/natural peatland’ (HBP) scenario, which is one of the scenarios detailed in its land use report, the [KC1] [MP2] UK’s net emissions from land use will be 40.2MtCO2e per year in 2030, 32.2MtCO2e excluding settlements.[4] This is 12.6MtCO2e per year higher than the level of emissions estimated to put the country on track to reach carbon neutrality from land use in 2040.
Our analysis, therefore, considered additional measures that could be implemented to achieve further emissions reduction. These fall into three categories:
  • Dietary change
  • Additional afforestation on grassland released from livestock production
  • Further sequestration measures through ecosystem restoration, improved soil carbon and the incorporation of biochar
Assessment of these measures are described for each category separately.

Dietary change
The HBP scenario assumes that meat consumption is cut by 20 per cent by 2050 (medium ambition), which means that, assuming a linear trajectory, meat consumption is reduced by 8.2 per cent by 2030. The CCC’s study also models the impact on emissions from a higher level of ambition, cutting meat consumption by 50 per cent by 2050, or by 20.6 per cent by 2030.[5] Both assessments assume that dietary changes in the UK result in a reduction in livestock numbers and land required for grazing.

Based on the projected agriculture emissions for business as usual, medium and high ambition, we calculated the emissions from agriculture that would be achieved if meat consumption were reduced by 25, 30 or 40 per cent by 2030, respectively, and compared those to the agriculture emissions for the medium scenario. This provided an estimate of the emissions that could be cut through a faster dietary shift (assuming no measures to reduce emissions from livestock are applied through the supply side).

The resulting additional emissions reductions are shown in the table below. Note that the dietary shifts to 25, 30 and 40 per cent assumes a similar change in diet as in the CCC’s HBP scenario, but it is based on an accelerated transition.

Final emissions reductions from diet were also adjusted to account for the fact that efficiency improvements in livestock production, included in the CCC’s HBP scenario, will reduce net emissions from the livestock sector (ie methane from livestock, manure and nitrous oxide from soils). This reduces the extent to which dietary shift affects emissions from agriculture. Based on the CCC’s analysis of the impact of individual efficiency improvements in farming practices [KC3] [MP4] ,[6] comparing in each case the high ambition scenarios versus business as usual in 2030, we estimate that efficiency improvements reduce emissions from agriculture by 6.7 per cent. Therefore, the impact of dietary shift was adjusted accordingly (see table below).
 
Dietary shift (reduction in meat and dairy consumption) Additional emissions reduction in 2030 (MtCO2e per year) Additional emissions reduction in 2030, including efficiency improvements (MtCO2e per year)
20.6% (CCC high ambition scenario) 4.1 3.8
25% 5.9 5.5
30% 7.5 7.0
40% 10.6 9.8
 
Additional afforestation
Reductions in livestock farming as a result of changes in the consumption of meat and dairy result in grassland being released. The land released can be used for alternative uses and climate change mitigation options and, in this study, we consider the potential for additional woodland creation.

Comparison of the land released under medium and high ambition scenarios for dietary change (CCC analysis), grassland released in 2050 amounts to a total of 2.7 million hectares under medium ambition and 6.9 million hectares under high ambition.[7] Therefore, in 2030, the high ambition scenario releases an additional 1.6 million hectares (compared to the medium ambition). This area is adjusted to account for increases in livestock grazing intensity (based on the CCC scenario analysis, which assumes about nine per cent of grassland area released by 2050)[KC5] [MP6] .[8] Therefore, total grassland released, assuming that the HBP scenario is combined with high ambition on diet, amounts to 1.5 million hectares.

We then estimate the emissions sequestration that could be achieved through more woodland creation on released grassland. Using the assessment from the CCC scenario, we estimate that planting rates of 50,000 hectares per year result in 5.3MtCO2e per year sequestration in 2030 (post-2016 woodland). This assumes a similar composition of broadleaf and conifer woodland as the CCC analysis (40:60 broadleaf:conifer, given the high planting rates). Based on this analysis, we also estimated the sequestration that could be achieved, if this planting rate were increased by 40 per cent, two thirds, and 100 percent. This is detailed in the table below.
 
Percentage increase in new woodland compared to CCC HBP scenario Additional woodland creation on spared grassland, compared to CCC scenario (hectares per year) Total area of woodland created by 2030, in addition to that already modelled in the HBP scenario (hectares) Emissions sequestered in 2030 from additional woodland creation (MtCO2e per year)
100% 50,000 550,000 5.3
67% 33,000 367,000 3.5
40% 20,000 220,000 2.1
 
Note that additional woodland modelled here is extra to the 50,000 hectares of new woodland per year modelled in the CCC’s HBP scenario. Therefore, total afforestation rates across the UK are 100,000, 83,000 and 70,000 hectares per year.[KC7] 

As evident from the table, the area used for woodland creation is lower than will be released from dietary shift. This suggests that there is additional grassland that could be used for other mitigation options.

Further sequestration measures
Additional sequestration measures include soil carbon sequestration, the restoration of salt marshes and use of biochar. These measures were not included in the CCC’s HBP scenario. The Royal Society estimates that their annual sequestration in 2050 amounts to 10MtCO2e, 0.3MtCO2e and 5MtCO2e, respectively (note that sequestration from salt marshes has been estimated based on a total area for UK salt marshes of 45,000 hectares, rather than 0.45Mha).[9] Assuming a linear increase in sequestration, starting from 2020, we estimate the following sequestration in 2030:

Soil carbon sequestration          3.3 MtCO2e per year
Salt marshes restoration           0.1 MtCO2e per year
Biochar                                      1.7 MtCO2e per year
 
Overall impact of additional emission reduction options in 2030
The combination of these three sets of measures, in addition to the measures included in the HBP scenario, is explored in the table below. The combined impact of diet, additional afforestation and further sequestration measures must be at least 12.6MtCO2e per year, to be able to cut emissions from land use to 19.5MtCO2e per year in 2030, putting the UK on track to meet net zero by 2040. Combinations that achieve these emissions reductions or more are highlighted in green.

Based on the assessment presented in the table below, the optimal combination of measures lies between combinations number 6 and number 9. This includes:
  • reduction in meat and dairy by 30 per cent;
  • tree planting rates of 70,000 hectares per year (ie 20,000 hectares on released grassland, in addition to the 50,000 hectares per year already included in the CCC’s HBP scenario);
  • further emissions sequestration through the restoration of salt marshes and soils; further research should assess the potential for biochar use, which has yet to be demonstrated at scale.
      Additional sequestration measures (restoration of salt marshes and soil carbon sequestration)
No. Reduction in red meat and dairy consumption by 2030 Rate of additional woodland creation (in addition to 50kha/year across the UK already included in the HBP scenario) Without biochar
 
Total emissions reduction in 2030 (MtCO2e per year)
With biochar
 
Total emissions reduction in 2030 (MtCO2e per year)
1. 20.6% 50kha/year 12.6 14.3
2. 20.6% 33kha/year 10.8 12.5
3. 20.6% 20kha/year 9.4 11.1
         
4. 25% 50kha/year 14.2 15.9
5. 25% 33kha/year 12.4 14.1
6. 25% 20kha/year 11.0 12.7
         
7. 30% 50kha/year 15.8 17.5
8. 30% 33kha/year 14.0 15.7
9. 30% 20kha/year 12.6 14.3
         
10. 40% 50kha/year 18.6 20.3
11. 40% 33kha/year 16.8 18.5
12. 40% 20kha/year 15.4 17.1
 

Endnotes
 
[1] Committee on Climate Change, 2018, Land use: reducing emissions and preparing for climate change; The Royal Society, 2018, Greenhouse gas removal
[2] Committee on Climate Change, 2018, ‘Charts and data for Chapter 2 – How land can be used to achieve greenhouse gas reduction goals (Excel)’, https://www.theccc.org.uk/publication/land-use-reducing-emissions-and-preparing-for-climate-change/
[3] By ‘carbon neutral’ we mean net zero across all greenhouse gases when carbon sinks are also taken into account
[4] Committee on Climate Change, 2018, ‘Charts and data for Chapter 2 – How land can be used to achieve greenhouse gas reduction goals (Excel)’, https://www.theccc.org.uk/publication/land-use-reducing-emissions-and-preparing-for-climate-change/
[5] A Thomson, et al., 2018, Quantifying the impact of future land use scenarios to 2050 and beyond, Table 10, p29 https://www.theccc.org.uk/wp-content/uploads/2018/11/Quantifying-the-impact-of-future-land-use-scenarios-to-2050-and-beyond-Full-Report.pdf
[6] See tables 3, 4 and 5 in A Thomson, et al., 2018, Quantifying the impact of future land use scenarios to 2050 and beyond – Final Report, https://www.theccc.org.uk/wp-content/uploads/2018/11/Quantifying-the-impact-of-future-land-use-scenarios-to-2050-and-beyond-Full-Report.pdf
[7] See table 10 in A Thomson, et al., 2018, Quantifying the impact of future land use scenarios to 2050 and beyond – Final Report, https://www.theccc.org.uk/wp-content/uploads/2018/11/Quantifying-the-impact-of-future-land-use-scenarios-to-2050-and-beyond-Full-Report.pdf
[8] See table 8 in A Thomson, et al., 2018, Quantifying the impact of future land use scenarios to 2050 and beyond – Final Report, https://www.theccc.org.uk/wp-content/uploads/2018/11/Quantifying-the-impact-of-future-land-use-scenarios-to-2050-and-beyond-Full-Report.pdf
[9] The Royal Society, 2018, Greenhouse gas removal; http://jncc.defra.gov.uk/pdf/UKBAP_BAPHabitats-08-CoastSaltmarsh.pdf

 

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