1. Climate mitigation by agriculture in Europe Pete Smith School of Biological Sciences, University of Aberdeen, Scotland, UK

2. Distribution of croplands globally

3. Distribution of croplands in Europe

4. Why croplands? European croplands (for Europe as far east as the Urals) lose 300 Mt C y -1 (Janssens et al., 2003) Mean figure for the European Union estimated to be 78 (SD: 37) Mt C y -1 (Vleeshouwers & Verhagen, 2002) Largest biospheric source of carbon lost to the atmosphere in Europe each year Highest uncertainty of all European fluxes There is significant potential to decrease the flux of carbon to the atmosphere from cropland, and for cropland management to sequester soil carbon.

5. Main figure from Janssens et al., Science 2003 Croplands in the overall carbon balance of Europe Cropland flux 0 200 400 600 D C B A missing fluxes ? land signal atmospheric signal 135 111 240 220 290 Carbon balance estimates European terrestrial C balance (Tg C a) )

6. Why croplands? European croplands (for Europe as far east as the Urals) lose 300 Mt C y -1 (Janssens et al., 2003) Mean figure for the European Union estimated to be 78 (SD: 37) Mt C y -1 (Vleeshouwers & Verhagen, 2002) Largest biospheric source of carbon lost to the atmosphere in Europe each year Highest uncertainty of all European fluxes There is significant potential to decrease the flux of carbon to the atmosphere from cropland, and for cropland management to sequester soil carbon.

7. Vleeshouwers & Verhagen (2002) Carbon fluxes in SOC in Europe (t C ha -1 y -1 ) in the 1st commitment period (business as usual scenario) CroplandsGrasslands Using mean soil organic carbon content Using mean soil organic carbon content plus S.D. Using mean soil organic carbon content minus S.D.

8. Why croplands? European croplands (for Europe as far east as the Urals) lose 300 Mt C y -1 (Janssens et al., 2003) Mean figure for the European Union estimated to be 78 (SD: 37) Mt C y -1 (Vleeshouwers & Verhagen, 2002) Largest biospheric source of carbon lost to the atmosphere in Europe each year Highest uncertainty of all European fluxes There is significant potential to decrease the flux of carbon to the atmosphere from cropland, and for cropland management to sequester soil carbon.

9. Can cropland GHG fluxes be reduced ?

10. Options for combating the greenhouse effect on European agricultural land More efficient use of animal manure Application of sewage sludge Return surplus cereal straw to the soil Convert to no-till agriculture Use surplus arable land to de-intensify production (extensification) Use surplus arable land to plant woodland Use surplus arable land to grow biofuels Smith et al. (2000)

11. C sequestration potential over 1 st commitment period Activity t C ha -1 yr -1 Mt C yr -1 Conversion arable to grassland 1.92178.49 Zero till 0.29 26.69 Straw 0.21 19.85 Farmyard manure (10 ton ha -1 ) 1.47136.38 CO 2 0.01 0.94 Temperature-0.06 -5.80 Vleeshouwers & Verhagen (2002)

12. Carbon mitigation potential / CO 2 -C offsets Smith et al. (2000) 0 10 20 30 40 50 60 70 ManureSludgeStrawNo-till Extensification WoodlandBioenergy Land Management Change Maximum Yearly C Mitigation Potential (Tg C y -1 ) - 0 1 2 3 4 5 6 % Offset of 1990 European CO 2 carbon emissions

13. Combined land-management options Smith et al. (2000) 0 10 20 30 40 50 60 70 80 90 100 110 B+NT B+S B+O B+O+NT W+NT W+S W+O W+O+NT E+NT E+S E+O E+O+NT Opt Scenario Maximum Yearly C Mitigation Potential (Tg C y -1 ) 0 1 2 3 4 5 6 7 8 9 % Offset of 1990 European CO 2 carbon emissions Europe’s 8% Kyoto target

14. Carbon sequestration potential Biological potential Biologically / physically constrained potential (e.g. land suitability) Maximum valueMinimum value Economically constrained potential Socially / politically constrained potential - estimated realistically achievable potential (~10% of biological potential) What is meant by C sequestration potential ? EU-15 can sequester up to 16-19 Mt C y -1 during the first commitment < 1/5 of theoretical potential ~ 2% of European anthropogenic emissions (Freibauer et al., 2004). Smith (2004)

15. Carbon sequestration potential (EU-15 cropland) 1 = Vleeshouwers & Verhagen (2002) 2 = Smith et al. (1997, 2000) 3 = Freibauer et al. (2004) 4 = Smith et al. (2004)

16. Is C sequestration important in the long term?

17. Why use C sequestration? IPCC TAR WGIII (2001) The energy / emission gap under different SRES scenarios Current yearly atmospheric C increase = 3.2 ± 0.1 Pg C y -1 Maximum yearly global C sequestration potential = 0.9 ± 0.3 Pg C y -1 Emission gaps here of up to 25 Pg C y -1 by 2100

18. So why use C sequestration? Critical period determining trajectory IPCC (2001)

19. Importance of non-CO 2 GHGs

20. Agricultural non-CO 2 GHG emissions in Europe

21. C mitigation potential with and without trace gases Smith et al. (2001) = CO 2 only = with trace gases 0 10 20 30 40 50 60 70 ManureSludge Straw No-till ExtensificationWoodlandBioenergy Land Management Change Maximum Yearly C Mitigation Potential (Tg C y-1) 0 1 2 3 4 5 6 % Offset of 1990 European CO 2 Emissions = CO 2 -C alone = CO 2 -C plus N 2 O and CH 4 Some land-management practices are influenced by including trace gases

22. SRES climate only SRES-B2 plus convert grassland to arable in 2000 Loss (2001-2100) of 37.7 t C ha -1 compared to B2 loss of 9.5 t C ha -1 due to climate change alone Land-use change – potential size of effect

23. Research Priority Areas Soil process studies in agriculture Data / inventory collation and meta-analysis Development of future land-use and land management scenarios Coupling of the C & N cycles (with N-IP) Assessment of total GHG budget (with N-IP) Mitigation options Overall aim: Quantify the carbon and GHG balance of European croplands for the 1990s, for the present, and in the future