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Is soil organic carbon sequestration really feasible? How to scale it up?


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GSP Webinar: RECSOIL: Recarbonization of Global Soils, 17 June 2020, Zoom platform. Presentation by Pete Smith, Professor of Soils and Global Change, Aberdeen University and Science Director of Scotland’s ClimateXChange.

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Is soil organic carbon sequestration really feasible? How to scale it up?

  1. 1. Is soil organic carbon sequestration really feasible? How to scale it up? Pete Smith Professor of Soils & Global Change, FRS, FRSE, FNA, F.EurASc, FRSB Institute of Biological & Environmental Sciences University of Aberdeen, Scotland, UK. E-mail: RECSOIL seminar, FAO, Rome, 7th April 2020
  2. 2. Soil organic carbon sequestration is feasible and the potential is large…
  3. 3. Soil C sequestration – global mitigation potentials Technical potential = 1.3 Gt Ceq/yr Economic potential at 20-100 US$/tCO2eq = 0.4-0.7 Gt Ceq/yr Paustian et al. (2016); Smith GCB (2016)
  4. 4. Bossio et al. (2020) Additional SOC storage potential for 12 natural pathways to climate mitigation
  5. 5. … and it has range of co-benefits…
  6. 6. Beneficial impacts for Soil C sequestration on ecosystem services and the UN SDGs Smith et al. (2019)
  7. 7. … but beware of some limitations…
  8. 8. Smith (2008) International Journal of Agricultural Sustainability 6(3),169–170 • “There are a number of well rehearsed arguments against reliance on carbon sequestration for tackling climate change, involving saturation of the carbon sink (the carbon is only removed from the atmosphere while the tree is growing or until the soil reaches a new equilibrium soil carbon level; Smith, 2005), permanence (carbon sinks can be reversed at any stage by deforestation or poor soil management; Smith, 2005), leakage/displacement (e.g. planting trees in one area leads to deforestation in another; Intergovernmental Panel on Climate Change (IPCC), 2000), verification issues (can the sinks be measured; Smith, 2004), and total effectiveness relative to emission reduction targets (only a fraction of the reduction can be achieved through sinks; IPCC, 2007)”.
  9. 9. Soil C Vegetation C Time since management change Cstock Management change Saturation – the time course of C sequestration • Sink saturation ~ 20-100 years • Sink strength declines towards new equilibrium Smith (2004a)
  10. 10. Permanence 25 35 45 55 65 75 85 1844 1894 1944 1994 2044 2094 Year TotalSOCto23cm(tCha -1 ) Management change Conversion to low-input cropland Manure treatment in red, Woodland in blue Smith (2005)
  11. 11. Leakage / displacement: are we actually sequestering carbon or just moving it about? Farm with more manure Farm with less manure Manure Manure Mineral N More manure here….but……..less manure here Effect over the whole cropland area = zero
  12. 12. …and we can scale it up with suitable monitoring, reporting and verification
  13. 13. Soil Monitoring, Reporting and Verification Smith et al. (2020)
  14. 14. Thank you for your attention