THE CONSEQUENCES OF INTERNATIONAL AGRICULTURAL RESEARCH ON GREENHOUSE GAS EMISSIONS AND GLOBAL CLIMATE CHANGE

1. THE CONSEQUENCES OF INTERNATIONAL AGRICULTURAL RESEARCH ON GREENHOUSE GAS EMISSIONS AND GLOBAL CLIMATE CHANGE L.V. Verchot, P. Grace, P. Sanchez, J. Ingram, C. Palm, R. Wassman, M. Fisher, R. Thomas, F. Chandler, W. Bowen, R. Reid, M. Wopereis and S. Waddington [L.Verchot@cgiar.org]

2. Background • Food production has tripled in the last 30 years in developing countries • This increase has been largely due to technological advances through improved varieties and intensification of agriculture

3. Questions • What is the effect of increased agricultural productivity on: • Atmospheric GHG concentrations • Terrestrial C • Have agricultural productivity gains mitigated or exacerbated climate forcing?

4. Approach:Case Studies • Green Revolution: Global Analysis • Alternatives to Slash and Burn: Humid tropics • Improved pastures: South America • Irrigation frequency in rice: Asia • Irrigated rice systems: W. Africa • Multiple cropping systems: S. Asia • Fodder banks: W.Africa • Tse-tse fly control: E. & S. Africa • Fertilizer reduction in maize systems: S. Africa

5. Case Study The Green Revolution

6. LUC soil: LUC biomass: N fertilizer application: N fertilizer production: Rice cultivation: Burning residues: Residue decomposition: Biological N fixation: Residue decomposition Rice cultivation CO2 CO2 CH4 N2O N2O CH4 CO2 CH4 CH4 N2O N2O N2O N2O CH4 GHG Emissions Included

7. GHG Emissions not Included • CH4 from livestock • CH4 and N2O from prescribed burning of savannas • N2O from application of animal manures

8. Green Revolution AnalysisAssumptions • Cereal yields remain constant 1965-1995 • Forest, then pastures used as new croplands • FAOSTAT as data source • GHG from available data or from IPCC default values for Asia, Africa and Latin America • N fertilizer usage remains at 1965 levels

9. Area Required to Meet Cereal Production in 1995 with 1965 Yields Without the Green Revolution the cultivated area in Asia, Africa and Latin America would have doubled.

10. Above-ground Biomass Emissions

11. Soil Emissions and Change in Soil C Stocks

12. Source CO2 from soil CO2 from vegetation CH4 from vegetation N2O from vegetation Total Saved from LUC +GR -GR 2.6 17.3 3.0 5.6 0.2 0.4 0.02 0.04 5.8 23.3 17.5 GHG Emissions Due to LUC(Gt C/y, 1965-95)

13. Source: Rice cultivation CH4 N fertilizer application N2O N fertilizer production CO2 Residue decomposition N2O Burning residues CH4 +N2O Biological N fixation N2O Total emissions LU Saved from LU Intensification Green Revolution With Without 3.7 5.2 1.3 0.4 0.8 0.3 0.5 0.5 0.3 0.3 0.1 0.1 6.7 6.8 -0.1 GHG Emissions Due to Intensification(Gt C/y, 1965-95)

14. Implications of Green Revolution • Saved 426 million hectares of forests and grasslands from clearing • If not, cultivated area would have about doubled in developing countries • Saved 583 million tonnes C y-1 from all activities • Equivalent to 1/3 of annual USA emissions (from ALL sources) • Virtually all the savings were due to savings in land use change

15. Case Study Pasture Improvement in S. America

16. Background • Pastures occupy 250 M ha in tropical SA • Loss of aboveground biomass is trivial when grasslands are converted to pasture • When forest is converted to pasture aboveground losses are high

17. Approach • Replicated plots • Poorly managed A. gayanus pasture (17 years old • Well managed pasture of B. humidicola (18 years old) • Measured soil C to 2 m depth

18. Soil C Stocks

19. Potential C Accumulation in SA Pastures Made from Grasslands

20. Conclusions • Well-managed pastures have the potential of accumulating significant C in the soil profile, compared to grasslands • Even if we factor in degradation the accumulation is likely to exceed 900 Mt • Conversion of forest to pasture will result in net C loss