D A R G A N M . W . F R I E R S O N
D E P A R T M E N T O F A T M O S P H E R I C S C I E N C E S
D A Y 1 0 : 0 5 / 0 1 / 2 0 1 4

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First, impact of agriculture on the environment
Then, how we expect agriculture to be affected by global warming

 Agriculture has a dramatic impact on the environment

Deforestation is 20% of world CO
2 emissions
Clearing Amazon rainforest for cow pastures in
Brazil
Slides courtesy
Jon Foley

 Agriculture has a dramatic impact on the environment

Deforestation is 20% of world CO
2 emissions
Clearing Amazon rainforest for soybean fields in Bolivia
(used primarily for cow feed)

 30% of GHG emissions come from agriculture in one way or another

Including deforestation, methane from rice/cows, & nitrous oxide from fertilizers
 Emissions from 1 kg of wheat: 1.1 kg of CO2e

1 kg of beef: 31.0 kg of CO2e
For 1000 calories a day of each, emissions in a year:
120 kg for wheat
4800 kg for beef
Source for CO2e numbers (for US): Sanders & Webber 2014

 The global footprint of agriculture: 40% of the
Earth’s land is used for pastures or croplands

Of this: 65% for pastures, 35% for croplands

 Irrigation of croplands

70% of freshwater usage goes to irrigating crops

 Aral Sea in 1973 and 2009

 1 liter of water per calorie on average (for cereals)

About 10 liters per calorie for meat calories
 Huge variations of this from location to location though
Drip irrigation could improve water efficiency where needed

 30 lbs of corn to make 1 lb of beef (USDA)

Much of the world’s food goes to feeding animals
Global use of crops:
60% to feed people
35% to feed livestock
5% for biofuels

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As people become richer, they tend to eat more meat
By 2050, forecasts suggest that we will have to
double our food production

Mostly not due to population increases (7B to 9B people)

Rather due to expectation that people will be eating more meat

 Expanding farmland by a lot would cause significant increases in deforestation
Source for lots of this: Foley et al 2011 (Nature)

 Developing countries could improve their yields substantially
Just need water & nutrients to do this
Would also improve resilience to climate change

Courtesy of David Battisti, UW Atmospheric Sciences
1.
Where do the Food Insecure live? What do they eat?
2.
Projections of climate at the end of the 21 st Century
3.
Climate Change and crop yields
4.
Impact on Tropical Ecosystems
5.
Summary

David Battisti in Indonesia talking to farmers
Indonesia work is with R. Naylor 1 , D.
Vimont 2 , W. Falcon 1 and M. Burke 1
(1) Stanford, (2) University of Wisconsin



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The book focuses a lot on higher latitudes
It’s true that Russia and Canada will have more farmland with global warming!
But this isn’t where the food insecure live…

Where do the Food Insecure live?
800 M people are malnourished today
• 95% are in the tropics/subtropics
Lobell et al (2008)
The food insecure are also the poor. They depend heavily on agriculture for both food and income.


Rice (26%)
 Wheat (17%)
 Sugar Cane (8%)
 Maize (6%)


Nuts (5%)
Cassava (Yuca) (4%)
 Other (34%)

Top producers:
1. China
2. India
3. Indonesia
4. Bangladesh
5. Vietnam
Rice

Rice
Source for production data: Food and Agriculture Organization of the UN

Wheat
Top producers:
1. China
2. India
3. USA
4. Russia
5. France

Maize (corn)
Top producers:
1. USA
2. China
3. Brazil
4. Mexico
5. Argentina

Cassava (Yuca)
Top producers:
1. Nigeria
2. Brazil
3. Thailand
4. Indonesia
5. Congo

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Average calorie consumption: 2800/day
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Developed countries: 3400, Developing: 2600, Least developed: 2100
30-40% of food is wasted
Total calories:


84% from plants (54% from cereals; rice and wheat are nearly
50%...)
16% from animals

1% from fish
40% of food comes from 17% of cropland that’s irrigated

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
Remember in “Floods and Droughts” we said…

Precipitation will increase in rainy regions
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Drying in many marginal continental regions
But there’s lots of uncertainty about precipitation

Upward motion can shift due to:

El Niño changes

One hemisphere warming/cooling more than the other

Shifts in storm tracks, etc.
Everywhere it’s expected to warm though

Projected Annual Average Precipitation:
“2080-2099” minus “1980-1999”
Drier Wetter
There is a robust drying of the subtropics, 20-35N&S.
Stippling is where the multimodel average change exceeds the standard deviation of the models
Scenario A1B

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Some cases where water limitation is most important

Including one study where the average precipitation
increases but there’s still water stress on crops!
Some cases where temperature is most important
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This is true in surprisingly many cases!
These examples will show some of the complexity of agricultural responses to global warming…
 Tropics are more vulnerable because there’s less variability there

~ 30% precip deficit
The 1998-2001 drought in the Middle East
20
0
- 20
1950 1970 1990 2000

•Iran: 80% of livestock lost
35 - 75% reduction in wheat & barley
•Afghanistan: 40% of livestock lost
•Pakistan: 50% of livestock lost
•Tajikistan: 50% of grain crop lost
By 2100, similar water stress on agriculture will likely be the norm in some locations in the tropics and subtropics due to global warming

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Most severe and extensive drought in 25 years
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Connected to La Niña conditions

80% of US agricultural land experienced drought, 57% had severe drought
In midwest, destroyed or damaged large amounts of feed corn and soybean crop
Beef is currently at its highest price in 30 years

Price up 35% in last 4 years
California drought will affect other foods soon
Source: USDA, Texas Beef Council

• About 240M people (fourth in world)
• 50% of the population in agriculture; 17% in poverty
• Rice is the staple crop in Indonesia:
– Two crops per year, depending on rainfall
– Mostly irrigated by run-of-the-river

Indonesian Rice and rainfall
Sep Dec
Crop 1
Mar
Crop 2
Jun Aug

Indonesia and Rice Today
 Main problem today: Late onset of the monsoon season

Delays the first planting (lengthens the hungry season)

Less overall planting

El Niño greatly affects annual rice production by delaying monsoon onset
 The typical El Niño event delays onset by ~30 days

Indonesia and Rice Today
 The typical El Niño event delays onset by ~30 days

 reduces total annual rice production by 1,000,000 metric tonnes (enough to feed 15M people for a year)
Impact is non-linear (threshold)
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Increases domestic and traded rice prices
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Forecasts of rice production based on El Niño supplied by Battisti’s team since 2001
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They make decisions like whether to start importing more based on this
Building on long-term relationships key

Projecting rainfall in Java/Bali in 2050
 How will the annual cycle of rainfall over
Java/Bali change with global warming?

Will a 30-day monsoon delay occur more frequently in the future?
 How will the impact of El Ni ño -based variability on rice production change in the future with global warming?

Projections of climate at the end of the 21 st Century (from IPCC)
– Focus on those changes that are “very likely” (i.e., those that are either deemed to have a greater than 90% chance to occur “based on quantitative analysis or an elicitation of the expert views”)

Projecting rainfall in Java/Bali in 2050
 Use the output from climate models with two emissions scenarios
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A2: relatively high greenhouse gas emissions
B1: low emissions, sustainable development
 Build empirical models to downscale and debias precipitation from climate models

Provides full range of projections to span the space of uncertainty

Findings: Java/Bali rainfall in 2050
 The monsoon rains will start 1-2 weeks later
 Rainfall will increase during the monsoon season
 The monsoon will end abruptly and the dry season will be drier
2000
2050
Aug Dec Apr Aug
Net impact: By 2050, the second season rice crop is marginal (too short for two crops) & highly vulnerable

 Adaptation: ways of planning for this
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Methods for water storage, water management
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Crop breeding for drought tolerance
Crop diversification
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Early warning systems

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Indonesia case is classic example of how
precipitation affects food production
Next we’ll show a case where temperature affects food production

Projected Jun-Aug Average Surface Temperature
Change: “2080-2099” minus “1980-1999”
Average of 21 climate models forced by Scenario A1B. Multiply by ~1.2 for A2 and
~0.66 for B1

Projections of future temperature
Temperature
Mean
1900-2000
Mean
2070-2100
“Shifting the distribution”: remember this?

Extreme Heat in Western Europe in 2003:
JJA temperature 3.6
° C above normal
• Italy: 36% maize reduction
• France: 30% maize and fodder (animal feed) reduction
25% fruit reduction
21% wheat reduction
By 2100, years of similar temperature stress on agriculture will be the norm throughout the tropics and subtropics due to the summer average temperature changes.
Refs: UNEP 2007; Easterling 2007; Earth Policy Institute 2006; Eurosurveillence 2005

Growing Season Temperature
France
Observed JJA Temp
(1900-2007)
2003

Growing Season Temperature
France
2080-2099
Observed JJA Temp
(1900-2007)
Projections use 22 climate models (IPCC AR4) forced by
A1B Emission scenario.
Variability taken from observations
2003

Projections of Growing Season Temperature
The Sahel
2080-2099
Sahel region of Africa
Not much variability of temperature from year to year currently
Future is predicted to be hotter than current record every year!

Projections of Growing Season Temperature
Summers from 2080-2099 warmer than warmest on record %
By the end of the 21st Century it will be much hotter everywhere
In most of the tropics/subtropics, the seasonal average temperature will very likely exceed the warmest year on record

Impacts of Climate Change on Food Security
Increasing temperature over the next 50 years will cause decreases in yield:
•
Decrease in grain filling
• Decrease in spikelet fertility (not as many seeds formed)
• Increased water stress
• Increased respiration
Important for all crops, but especially for wheat, rice, soybeans and maize
Wheat Yield in
Yaqui Valley, MX
Jan-Mar Night Temp (
°C)
Lobell 2007

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Reduced yields of wheat, rice, maize, and soybeans in the tropics/subtropics
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Approximately -10% for each degree warming
Estimated reduction of 30-40% by 2100 in India, Africa,
Middle East, Central America, etc
Reduced nutritional content (especially in wheat and rice)

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Changes in pests and pathogens
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Many are worse in warmer temperatures, but expected impacts are not well-understood
Increased CO2 and plants

Enhanced growth rates for some plants (benefits tend to be limited to extratropics though)


By 2100, growing season temperatures will very
likely exceed the warmest on record throughout the tropics and subtropics

20-40% reduction in yields of major crops
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In subtropics, crops will be further stressed by reduced rainfall
Increased CO
2
(fertilization) effect is small when nitrogen limitation and ozone increase are taken into account

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Improve efficiency in developing countries

Could produce up to 50% more food this way
Shifts in diet away from meat
Less food waste

30% of food is wasted worldwide
Reduce agricultural greenhouse gas emissions

Don’t cut rainforest, less overfertilizing
Adaptation to climate change
Goals of Climate Change, Agriculture and Food Security