FEEDING A HOT AND
HUNGRY PLANET
Tim Searchinger
Princeton University
tsearchi@princeton.edu
Ag’s Contribution to World
Greenhouse Gases ~ 30%
CO2 from
Energy
Use
1 Gt
2%
2004
N2O and
NH4
6 Gt
12%
Ag Land
Expansion
8.5Gt
17%
Non-Ag
33.5 Gt
69%
49 Gt Total
• Nitrous oxide –
fertilizer, manure
• Methane – cows, rice,
manure, biomass
burning
• Energy – farm
machinery, fertilizer,
irrigation pumps
• 33 million acres/yr
gross deforestation
(IPCC 2007; Bellarby 2008 , in CO2 eq.)
Land Use Change
Biofuels send price signal:
Undernourished People and Recent Changes
Source: FAO. 2009. The State of Food Insecurity In the World, 2008
$14
Trends in Cereal Crop Prices, United States Season Average
$12
Season average price, $/bushel
2000 Constant $
$10
$8
Barley
Corn
$6
Oats
Sorghum
Wheat
$4
$2
$0
Source: USDA, NASS
- 16% of world malnourished
- 1/3 of children in
developing world stunted
- 30 million babies born
impaired due to lack of natal
nutrition
- 5 million children die
annually from causes related
to lack of nutrition
The Hunger Challenge
Source: Keyzer 2006
Food for a Week, Darfur Refugees, Chad
© 2007 PETER MENZEL PHOTOGRAPHY
Food for a Week, Germany
© 2005 PETER MENZEL PHOTOGRAPHY
4.0%
World Cereal Yield Growth 1965-2006
3.5%
5 year average annual change , percent
3.0%
2.5%
5 year average percent change in cereal World
5 year average percent change in Population World
2.0%
Linear (5 year average percent change in cereal
World)
Linear (5 year average percent change in
Population World)
1.5%
1.0%
0.5%
0.0%
1965
1970
1975
1980
1985
1990
1995
2000
2005
Tilman, Forecasting Global
Agricultural Driven Environmental
Consequences
Potential yield and yield gap at a global scale
2.5
2
Sweden
1.5
Asia
Denmark
Ireland
UK
Belgium
Germany Netherlands
Europe
North America
South America
Zambia
France
Zimbabwe
Egypt
3
Namibia
1
Africa
Oceania
-3
)
Ireland Sweden Denmark
0.5
Rwanda
2000
2.5
UK
R2 = 0.8788
2
0
0
Crop Water Productivity (kg m
Crop Water Productivity (kg m -3)
3
4000
Asia
6000
8000
Europe
10000
North America
Yield (kg1.5
ha -1)
South America
Africa
Eritrea
1
Oceania
2
R = 0.7859
Sudan
0.5
Mali
Chad
0
0
2000
4000
6000
8000
Yield (kg ha -1)
10000
12000
14000
GEPIC Outputs:
global map of wheat yield
crop water productivity of wheat
Areas of Water Stress
Can we limit LUC for food alone
Optimism
• Big yield gaps
• Much food waste
• Biotechnology
• Livestock intensification
potential
Pessismism
• Declining trend lines
• Irrigation limits
• Improved knowledge for
tropical forest agriculture
• Population?
• Climate change (high
temperature; declining
snowpack)
IPCC SRES Scenarios
Predicted Emissions from Land Use Change
Year
B-1
B-2
2020
2.2
0
2050
-0.4
-0.2
Other Uses of Land
• More cropland and pasture for food –200-500
million hectares by 2050
• Terrestrial carbon sink – 9.5 GT CO2/yr
• Avoided deforestation potential – 9 Gt/year
• Afforestation mitigation potential – 4 Gt/year
• Restore peatlands – 1.3 gigatons/year
All from IPCC 2007 Mitigation Report, chapters 8 & 9
Agriculture Mitigation Potential at
$100/t
Some Technical Options
Somewhat Known
• Crop & livestock yield
gains
• Chickens, tilapia over
beef
• Manure biogas
• Improved N use efficiency
• Livestock feeding
• Pasture improvement
• Some rice water
management
Innovations Required
• Perennial feed crops &
other new cropping
systems
• Cover crops?
• Cow stomach bug
changes
• More nitrogen crops
• Upland or alternative rice
• New nitrification inhibitors
• Biochar
Biofuels & Greenhouse Gases
Conventional
approach
But . . .
Land grows plants
(carbon) anyway
* forest
* food
Only ADDITIONAL
plant growth helps
Direct Effects of Diverting Crops to Biofuels –
No Change in Emissions
Corn uptake
Corn uptake
Car, gasoline
Car, ethanol
Indirect Scenario 1 – Ethanol Leads to Less Crop
Consumption for Food, which Reduces CO2
Crop uptake
Crop uptake
Car, gasoline
Livestock & human
respiration
Car, ethanol
Reduced
livestock
& human
respiration
Indirect Scenario 2 – Ethanol Leads to Yield Growth on
Existing Farmland to Replace Diverted Crops, which Absorb
More Atmospheric Carbon and Reduces CO2
Crop uptake
Car, gasoline
Car, ethanol
Increased yields, which
absorb more carbon on
the same land but may
involve increased
emissions from inputs,
such as nitrous oxide
GHGs from Nitrous Oxide For Yield Gains
Through Fertilizer (assuming 7 extra
additional lbs of fertilizer/bushel of corn)
N2O Formation Rate
Greenhouse gases
(CO2 eq.)/km
2%
401
3%
603
4%
803
5%
1003
6%
1204
Compare 316 g/km from land use
Implied Yield Growth by 2020
Scenario 10.2% Transport
Fuel(Etech 4)
Crop
Cereals
(corn,wheat
Oilseeds
(soy, rape)
Sugar (cane)
Palm
Biofuels,
adjusted for
by products
Non Biofuel
food demand
Biofuel and
Non Biofuel
1996-2006
Trend
0.8%
1.8%
2.6%
1.3%
0.9%
5.0%
2.2%
0.6%
3.2%
5.5%
1.5%
0.8%
3.0%
3.9%
6.9%
1.9%
Viewed as Opportunity Cost
Carbon Benefit
• 3 t/ha/yr – corn ethanol – GREET (incorporating by-product
credit)
• 8.6 t/ha/yr – cellulosic ethanol – GREET (swtichgrass at 18
t/ha/yr, 359 l/t)
Carbon Cost
• Fallow land - forest regeneration temperate, 7.5-12 t/ha/yr
• Forest regeneration tropical – 20+ t/ha/yr
• Existing forest (lose 600-1000 tons) 15-35 t/ha/yr (over 30
years)
• Existing grassland/savannah (lose 75-300 tons), 2.5-10 t/ha/yr
(over 30 years) plus lost forage
Bioenergy
How?
• Large % of potential arable land – IPCC 2007 chapter
8 (based on Smith 2007) 1.3billion hectares and/or
• All forest growth in excess of harvest (Smeets
2008)and/or
• All “abandoned” cropland (Hoodwijk (2004) and/or
• Hundreds of millions of hectares of “grazing” or “other”
land – savannah (Fischer 2001; Smith 2007)
Recounts existing forest, forest re-growth, net terrestrial
carbon sink, land counted for grazing
The Big Issue
Exemption for Bioenergy
Under a Cap & Trade System
• IPCC 2000 Land Use Report (p. 355): Because
“fossil fuel substitution is already ‘rewarded’” by
excluding emissions from the combustion of
bioenergy, “to avoid underreporting . . . any
changes in biomass stocks on lands . . .
resulting from the production of biofuels would
need to be included in the accounts.”
Natural Forest
(Melillo, Gurgel, et al. 2008)
Natural Forest
Natural Forest (“Deforestation”
Scenario)
Natural Forest
Wise et al., Science 324:1183
(2009)
National Academy of Sciences
(May 2009)
• "If food crops or lands used for food production are diverted to
produce biofuels rather than food, additional land will probably be
cleared elsewhere in the world and drawn into food production. The
greenhouse gas emissions caused by such clearing of land,
especially forests, will decrease or even negate the greenhouse-gas
benefits of the resulting biofuels." p. 79
• "Producers need to grow biofuel feedstocks on degraded agricultural
land to avoid direct and indirect competition with the food supply and
also need to minimize land-use practices that result in substantial
net greenhouse-gas emissions." p. 79
Other 2008/09 Studies – Similar
Conclusions
• UK Renewable Fuels
Agency (Gallagher
Review)
• EU Joint Research
Center
• World Bank
• FAO
• Netherlands
Environmental
Assessment Agency
• OECD
• European Economic
and Social Committee
• Scientific Committee
on Problems of the
Environment
• British Royal Society