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_at_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
ApproachCase 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

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Case Study

• The Green Revolution

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GHG Emissions Included

• 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

7
GHG Emissions not Included

• CH4 from livestock
• CH4 and N2O from prescribed burning of savannas
• N2O from application of animal manures

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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

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Area Required to Meet Cereal Production in 1995
with 1965 Yields
Region Yield (t ha-1) Yield (t ha-1) Area (M ha) Area (M ha) Area saved (M ha)
1965 1995 GR -GR GR Saving
Africa 0.8 1.1 27 53 26
Asia 1.4 2.9 48 405 358
LAC 1.4 2.5 6 48 42
Total 81 507 426
Without the Green Revolution the cultivated area
in Asia, Africa and Latin America would have
doubled.
10
Above-ground Biomass Emissions
Region CO2 (Gt) CO2 (Gt) CH4 (Mt) CH4 (Mt) N2O (Kt) N2O (Kt)
GR -GR GR -GR GR -GR
Africa 4.6 9.0 15.5 30.7 107 211
Asia 4.5 4.5 15.4 15.4 106 106
LAC 2.0 7.0 6.8 23.7 47 163
Total 11.1 20.5 37.7 69.8 260 480
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Soil Emissions and Change in Soil C Stocks
Region CO2 (Gt) CO2 (Gt) DC Stock (Gt) DC Stock (Gt)
GR -GR GR -GR
Africa 2.8 5.5 0.8 1.5
Asia 6.3 53.5 1.7 14.6
LAC 0.6 4.8 0.2 1.3
Total 9.7 63.8 2.7 17.4
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GHG Emissions Due to LUC (Gt C/y, 1965-95)

• 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

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GHG Emissions Due to Intensification(Gt C/y,
1965-95)

• 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

• 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

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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

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Case Study

• Pasture Improvement in S. America

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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

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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

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Soil C Stocks
Depth (cm) Savanna A. gayanus B. humidicola
0 - 20 7.0 7.6 8.8
20 100 12.6 14.7 17.9
total 19.6 22.3 26.7
deeper than 20 cm 64 66 67
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Potential C Accumulation in SA Pastures Made from
Grasslands
Total Pasture Area (Mha) Potential Accumulation (Mt)
Br. Shield 40.8 1713
Orinoco Basin
Colombia 0.2 4
Venezuela 2.4 4.0 86
Total 45 1803
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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