Pathways of Agricultural Expansion Across the Tropics: Implications for C Payback Times Holly K. Gibbs David H. Smith Conservation Research Fellow Woods Institute for the Environment Food Security and Environment Program Stanford University Collaborators: Jon Foley, Matt Johnston, Navin Ramankutty CRC LCA Meeting, October 21, 2009
Biofuels and the Tropics navigating the debate Carbon payback time from biofuel production? Constrain the debate with new data & refined analysis Where will new biofuel cropland come from? New analysis identifying ag expansion pathways Data sources, gaps and future directions
Net carbon flux from biofuel expansion? Carbon Payback Time = Cland source - Cbiofuel crop Biofuel C savings / ha / yr How many years needed for the biofuel C savings from avoided fossil fuel combustion to offset C losses from converting land source?
Step 1: How much carbon is emitted per hectare of expanding cropland? Gibbs et al. (2007) ERL, Gibbs and Brown (2007)
Step 1: How much carbon is emitted per hectare of expanding cropland? Biomass Carbon of Tropical Land Cover Types (t C / ha) Americas Sub-Saharan Africa Southeast Asia 2 Pan-Tropical Humid Moist Dry Humid Moist Dry Humid Moist Dry Humid Moist Dry Forests 197 132 130 204 156 76 229 109 82 210 132 96 Disturbed Forests 100 68 67 104 80 40 116 56 43 107 68 50 Savanna 64 43 42 67 51 24 75 35 26 69 43 31 Grassland 8 8 4 8 8 4 8 8 4 8 8 4 Degraded Land 1 1 1 1 1 1 1 1 1 1 1 1 Annual Cropland 6 7 7 4 3 5 5 5 5 5 5 5 Sugarcane 11 14 15 5 9 14 13 13 14 10 12 14 Oil Palm 71 79 72 17 23 45 88 77 77 58 60 65 Coconut 95 93 93 68 41 29 67 66 74 77 66 65 Land Source C Stocks Feedstock C Stocks Gibbs et al. (2008) Env. Res. Letters
Step 2: Annual biofuel C savings per ha? Monfreda et al. (2007)
Step 2: Annual biofuel C savings per ha?
Soy-biodiesel saves ~0.3 t C / ha -yr
Sugarcaneethanol saves ~3 t C / ha -yr
Carbon Payback Time? PEAT SWAMPS Gibbs et al. 2008, Env Res Letters
How realistic are these what if scenarios?
Why will agriculture expand in the tropics? Cheap land, cheap labor = high profits Much of the tropics is biophysically suited for soy, oil palm or sugarcane production Tropical ag expansion increasingly responsive to global markets
Why will (biofuel) agricultural land expand in the tropics? Current Cropland Potential Cropland Industrialized countries have smaller land base FAO 2003, FAO SOFA 2008
Why will (biofuel) agricultural land expand in the tropics? 2/3 of world s available land in Tropics? Most cropland increases occurred in Tropics, 1980-2007 FAO 2003, FAO SOFA 2008
Expansion is inevitable
Land sources for expanding crops?
Analyzed library of Landsat images from FAO Detailed satellite data with 30m by 30m spatial resolution Random sample of Landsat locations or sites Snapshots of land cover for 1980, 1990 and 2000 Most detailed image processing to date FRA 1990, 2000
Used Landsat to track agricultural expansion Detailed satellite data with 30m by 30m spatial resolution Detailed Classification & Change Detection FRA 1990, 2000
Land Sources Across the Tropics? 1980-2000 Gibbs et al., in review Forests and disturbed forests are primary land sources
Land Sources for New Agricultural land? Gibbs et al., in review
Land Sources for New Agricultural land?
Land Sources for New Plantations? Gibbs et al., in review
What about degraded land? Great idea with many challenges High cost / low profit Requires input of water and fertilizer Could result in leakage or displacement of land insecure people Often easier to get government concessions for forests
Will oil palm expand into degraded land? Planting Harvest 3-5 years Not likely..oil palm producers need revenue from logging forests while waiting for plantations to mature
LUC Data Gaps and Limitations Most studies focus on net changes in forests or croplands, but neglect the pathways Not crop specific Extremely poor mapping of degraded land No attribution information in terms of expansion for food, feed, fuel Current information on agricultural expansion pathways not available RFS2 exemplifies need for improvement
Take Home Messages: Crop-based biofuels produced in tropics unlikely to provide carbon benefits today or in the future Forests are the land source for most new agricultural land in tropics We should incentivize forest conservation and keep the carbon on the ground Need improved, rapid assessment of agricultural expansion pathways for direct and indirect LUC
Funding: David H. Smith Conservation Research Fellowship, Stanford GCEP grant hgibbs@stanford.edu
EXTRA SLIDES
Potential sources for expanding agricultural land Simplified land cover categories
Land Sources for New Agricultural land? Gibbs et al., in review
Land Sources for New Agricultural land?
Need improved degraded land data Degraded / marginal / abandoned land in SOUTH AMERICA Gibbs 2009
Transformation of Tropical Ag? Dramatic yield increases through management? What about scenarios for advanced biofuels?
Transformation of Tropical Ag? Dramatic yield increases through management? What about scenarios for advanced biofuels?
C Payback with Yield Increases? Payback time reduced by 30-50% Gibbs et al. 2008, Env Res Letters