Transcript 11-28-food futures

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TODAY
Food Futures: Will there be enough food for
the 21st century?
Opportunities to improve output
Feeding the World: A Challenge for the 21st
Century. 2000. Vaclav Smil. MIT Press.
Institutional & Policy Changes to end hunger
Ending Hunger in Our Lifetime. 2003. CF
Runge, B. Senauer, PG Pardey, & MW
Rosegrant. IFPRI & Johns Hopkins U. Press.
© T. M. Whitmore
QUESTIONS?
• Hunger model
• Irish Famine Example
• Nutrition Transition model
© T. M. Whitmore
Reasons for concern I:
Population Growth
• Population growth to 8-10 billion by
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2050 (50% more than today!)
All in less developed world (China = India
each ~ 1.5 b)
© T. M. Whitmore
Reasons for concern II:
Dietary transitions
• Moving up on the food chain
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Traditional diets => ~2400 kcal; 10%
animal
Improved diets => ~3000 kcal; 25%
animal
Increased animal fraction => 4-5 times
more animal feed (plant material) needs
to be produced
Overall need ~ 2x current harvest to get
improved diet by 2050 for everyone
© T. M. Whitmore
Reasons for concern III:
Changes in agriculture
• Increases in pollution, erosion, and
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decreases in water availability
potentially =>
Slow growth or even decrease
Already slowing rates of growth of grain
production per capita
© T. M. Whitmore
Raising Output:
4 major areas of concern
1. Photosynthesis and crop productivity
limits
2. Land, water, and nutrient (NPK) limits
3. Agroecosystems and biodiversity
4. Environmental change
© T. M. Whitmore
1) Photosynthesis & crop productivity
limits
• There is an energetic limit:
Photosynthesis is < 5% efficient in
converting sunlight to vegetative matter
(even less if water or nutrients are short)
One way to address this is to improve the
harvest index (= edible part/total biomass)
This is an area of possible progress
 traditional wheat 20 - 30%
 green revolution wheat 35 - 50%
© T. M. Whitmore
2) Land limits I
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Agricultural land limits
~ 1.5 giga (109) ha now cultivated and 1.6
giga ha (rainfed) potentially usable
Most area available for expansion in S.S.
Africa & S. America savanna
© T. M. Whitmore
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2) Land limits II
Land use needed per-capita
Traditional vegetarian diet =>
 0.7-0.8 ha /capita
Chinese diet (2800 kcal; 15% animal)
 ~ 1.1 ha/capita
Rich Western diet
 ~ 4.0 ha/capita (much wasted and high
meat fraction)
Better diet with some animal protein
 ~ 1.5-3.0 ha/capita
if 10 b people in 2050 =>
 need 800 million ha to 3 gig ha (3000
million)
Thus, no fixed limit due to amount of land if
diet not excessive & all available land
© T.used
M. Whitmore
2) Land limits III
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If 10 b people in 2050 =>
Need 800 million ha to 3 gig ha (now use 1.5
gig ha)
Thus, no absolute limit due to amount of land
if diet not excessive & all available land used –
AND food can be moved from surplus areas to
deficit areas
Regionally per-capita land availability is more
problematic for 2050
OK in Latin America
Adequate in Sub-Saharan Africa & Mid-East
Problematic in South & East Asia
© T. M. Whitmore
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2) Water limits I
Water: – in most systems water is the most
important limit most years
Photosynthesis uses/needs lots of water
also add evaporation and transpiration
250 - 500 mm water needed per ha for lowyielding crops
800 - 1000 mm water needed by high
yielding crops
Current irrigation
~ 250 million ha (only 8 m ha in 1800)
~ 17% of all agriculture land
Creates 40% of all food
© T. M. Whitmore
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2) Water limits II
Current Water Use
Currently 5-7% of all available fresh water
runoff used for agriculture
Even if water use only grew to match
population => by 2050 agriculture will need
1/3 of all available fresh water
© T. M. Whitmore
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2) Water limits III
Crop and animal water use efficiency
Small grains and pulses => 0.25 m3 of water
/million joules energy to humans (or about 1
liter per kcal)
Animals via grain and feed => 25.4 m3
water/m joules energy to humans (100x
more!) or ~ 100 liters per kcal
© T. M. Whitmore
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2) Water limits IV
Water use in diets
Vegetarian diet (2500 kcal/day) =>
 0.9m – 1.2 million liters/capita/year
Rich world diets (more kcal and more animal
foods) =>
 >> 2.0 m l/capita/year
Improved diets (more kcal and more animal
foods than traditional vegetarian) =>
 ~ 2 million l/capita/year
So – 10 b people =>
 20,000 m3 water or ~ 2/3 of ALL global
runoff (assumes 2000 m3/capita/yr)
© T. M. Whitmore
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2) Nutrient limits I
Crop nutrient (NPK) limits
Typically need 10s of kg P & K and 100s kg N
per ha in modern high output agriculture
Complete recycling of ALL organic residues
from all harvested land and confined
animals NOT able to supply all the NPK
needed for high-yield agriculture (i.e., more
removed by harvesting than could be
replaced)
Only way to feed 10 b this way (all organic)
would be to increase cropped area 2 - 3
times (e.g., all tropical rainforests)
© T. M. Whitmore
2) Nutrient limits II
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Nitrogen is the key element
We do not know annual rates of biofixation
of N with certainty
Clover alfalfa etc. fix about 150-200 kg/ha
Beans about 70-100 kg/ha
Bacteria in rice fields ~ 30 kg/ha
Earth may be able only to support 3-4 billion
w/o synthetic N added
© T. M. Whitmore
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2) Nutrient limits III
Nitrogen continued
50 gm protein/capita/day for 6 b people in
2000 => only 19 m tons Nitrogen/yr
removed from soil
Current synthetic nitrogen production about
80 m tons/yr
Energy cost to produce N:
40 giga joules/ton of N fertilizer (40%
energy; 60% feedstock)
This equals only 7% of world's total natural
gas so energy is not a limit
© T. M. Whitmore
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2) Nutrient limits IV
Phosphorus (P)
Complete recycling not able to support highyield farming
But - mined rock not in short supply
Potassium (K)
needed in even smaller quantities
Thus only N is a nutrient bottleneck
© T. M. Whitmore
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3) Agroecosystem & Biodiversity
Basic ecology
=> Increased species diversity => increased
net primary productivity and nutrient
retention
But NO clear link between natural system
stability and diversity
© T. M. Whitmore
3) Agroecosystem & Biodiversity II
• Concern I: a very narrow biotic base of
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modern ag
Traditional systems use far more species than
do modern monocultures (e.g., wheat in USA
plains)
250,000 higher plants known; 30,000 edible;
7,000 have been cropped
Only 15 major crop species
15 species produce 90% of all food
Corn, wheat, rice produce 2/3 kcal and 1/2
plant protein!
© T. M. Whitmore
3) Agroecosystem & Biodiversity III
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Crop rotations, intercropping, and new crops
Perfected rotations => better yields, soil
protection, reduce pests (but not all are so
good)
Introduction of legumes in rotations can be
very helpful
Microorganisms (soil flora an fauna
primarily)
 diversity apparently NOT down overall
but this is NOT a well studied field
 correct applications of modern inputs
does not seem to hurt soil microbes (but
not well studied)
© T. M. Whitmore
4) The last major concern is
Environmental Change
• Changing soils
• Environmental pollution
• Climate change
© T. M. Whitmore
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Changing soils I
Erosion - most talked about issue
Mismanagement => excess erosion on 180 m
ha crop fields (about 1/5 of all cropped
land)
Data are uncertain and scarce
Varies with soil type and cropping type
BUT evidence is lacking to prove widespread
productivity loss
© T. M. Whitmore
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Changing soils II
Qualitative soils degradation - often subtle
and long-term
Even more difficult to prove or gather data
Again little hard data to prove widespread
problems (but vice versa)
Salination is easier to show - but not
significant in global sense
Loss of productivity hard to see because of
changes cultivars, fertilization, irrigation,
etc.
Retention of soil organics via using crop
residues etc. probably key here
© T. M. Whitmore
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Environmental Pollution I
Has been implicated in reducing crop yields
Agriculture is a major polluter itself
Nitrogen issues
Compared to pre-industrial era humans now
have doubled all inputs of nitrogen to soils &
atm.
Nitrates are widespread contaminates in
surface and sub-surface water
Atmospheric deposition of nitrogen should
=> increased production – but good data
scarce
© T. M. Whitmore
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Environmental Pollution II
Ozone
Loss of stratospheric ozone => higher levels
of ultraviolet radiation => damage to crops
High levels of surface ozone also degrades
agriculture production in places like W
Europe; E North America; E Asia
© T. M. Whitmore
Climate Change I
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Mostly due to increase in greenhouse gasses
Key issues for agriculture
Surface heating (~ 2º C - greater more
pole-ward)
Intensified water cycling (more in high
latitudes)
Uncertain local effects but droughts or
surplus water quite possible
© T. M. Whitmore
Climate Change II
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Probably increasing instability in climate
system (i.e., storm intensity and variability)
Agriculture is a major contributors to
greenhouse warming
Releasing CO2 form biomass and soils;
N2O emissions from fertilizers;
Methane from rice fields and cow farts
© T. M. Whitmore
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Climate Change III
Consequences for agriculture
Overall agriculture output may not change
much in near term – but regionally there
may be problems
Increased CO2 => increased crop yields
(assuming no other constraints); lower
water loss thru leaves (transpiration);
better ability to withstand env. pbms. etc.
Doubled CO2 should boost yields in well
fertilized crops of about 7-30% (C3 species
benefit most - all staple cereals except
corn and sorghum)
© T. M. Whitmore
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Climate Change IV
Consequences for agriculture II
Rising temps
Improve efficiency of C3 plants (if too high
=> lower yields)
Temporal timing also key (all in summer? all
in winter? – all this is unclear); but too hot
could => drought-like stress
Increase cropping area overall in higher
latitudes
© T. M. Whitmore
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Climate Change V
Consequences for agriculture III
More rapid water cycling
More water available for irrigation but
regionally much more uncertain
Changes may be gradual so adaptation may
help
Regional scenarios: high latitude areas may
benefit (Canada, Russia); drier tropics and
sub-tropics may be big losers (SS Africa
etc)
© T. M. Whitmore
Changes in crop yield by
the 2080s, under scenarios
of unmitigated emissions
Rosenzweig, C., M. L. Parry, G. Fischer, and K. Frohberg. 1993.
Climate change and world food supply. Research Report No. 3.
Oxford: University of Oxford, Environmental Change Unit.
Changes in crop yield by the
2080s, under scenarios of
stabilization of CO2 at 750 ppm
Changes in crop yield by the
2080s, under scenarios of
stabilization of CO2 at 550 ppm
Opportunities to improve things:
Higher cropping efficiency via more
efficient fertilization
• Late 1990s global use of N fertilizers (80 m
tons/yr) about 60% to 3rd world – in future
will account for more (predicted to grow at
2%/yr)
• Most need in SS Africa where soil losses in
NPK are not matched by fertilizer applications
© T. M. Whitmore
More efficient fertilization II
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Asia is reverse – HYVs and heavy fertilizer
use
Problem is much applied nutrient does not
serve plants at all (leaching, and erosion
especially of N) and pollutes
N losses are commonly 10-15% of applied
ammonia and 30-40% of manures (aggregate
perhaps 45-50% loss in rain-fed and 30-40%
loss in irrigated)
© T. M. Whitmore
More efficient fertilization II
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Reducing fertilizer losses
Soils testing
Use of more stable fertilizers
Unbalanced (excessive) N use is a main
problem
Proper timing
Proper application
© T. M. Whitmore
More efficient fertilization III
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Increased reliance on biofixation (rotation
with legumes primarily and use of green
manures) and nutrient recycling
N recovery from green manures is higher
than for synthetic N fertilizers
Problem is needed output is forsaken by
growing of green manures
Choosing cultivars that require less (e.g,
Brazil’s choice of soy with low N need => low
use of N fertilizers)
Possible to inoculate fields with N-fixing
bacteria to set up self-sustaining N fixation
© T. M. Whitmore
Better use of water
• Water seldom priced appropriately to regulate
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use
Irrigation efficiencies
Losses maybe 60-70% of initial total; 20-30%
improvements possible => enough water to feed
100 m more people
Reduce loss in canals
Plant more water efficient crops
Better timing of water application
Simple devices to judge soil water need
Manage tillage to reduce soil water loss
Use new efficient pumps and motors
© T. M. Whitmore
Rationalizing animal food production
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Justification for animal use
There is no need to eat animals to lead
healthy lives
But humans seem to be adapted to omnivory
by evolution
Globally humans eat ~ 10-20 kg annually - a
quite small amt. by US standards (70-110 kg
annually + 300 kg milk)
Adding meat and milk to diets is an “easy”
way to improve protein, calcium, vitamin, and
etc.
© T. M. Whitmore
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Animal food production II
As long as animals eat foods we cannot they do
not compete with humans
But the problem is that increasingly we
feed grain to animals; in 1900 ~10% of grain
to animals; by late 1990s ~45%!; > 60% in
USA
If all grain fed to animals were devoted to
humans => 1-3 billion could be fed!!
© T. M. Whitmore
Animal food production III
• Efficiencies and resource use of animals
Milk: inherently efficient energy conversion
 feed: 30-40% of feed to edible energy; ~3040% of feed to protein
 land: need about 1-1.5 sq meter land per
million kcal; 19-28 sq meter land per kg
protein
 water: 10-15 gm water/kcal; 200-300 gm/g
protein
Eggs:
 feed: 20-25% feed to edible energy; ~ 3040% of feed to protein
 land: need ~ 1.5-2 sq m / m kcal; 19-25 sq
meter land per kg protein
 water: 1.5 gm water/kcal; 15 gm/g protein
© T. M. Whitmore
Animal food production IV
• Efficiencies and resource use of animals
Chickens:
 feed: 15-20% feed to edible energy; ~ 2030% of feed to protein
 land: need ~ 2.5-3 sq m / m kcal; 13-15 sq
meter land per kg protein
 water: 6 gm water/kcal; 50 gm/g protein
Pork: inherently efficient due to low basal
metabolism; rapid reproduction and growth
 feed: 20-25% feed to edible energy; ~ 1015% of feed to protein
 land: 5 gm water/kcal; 150-200 gm/g protein
 water: need ~ 2.0-2.5 sq m / m kcal; 80-100
sq m/kg protein
© T. M. Whitmore
Animal food production V
• Efficiencies and resource use of animals
Fish:
 feed: farmed carp etc. 15-20% feed to
edible energy; ~ 20-25% of feed to protein;
 farmed salmon 35-40% feed to edible
energy; ~ 40-45% of feed to protein (but
carnivorous => need high protein feed)
Beef: US-style feedlot
 feed: 6-7% feed to edible energy; ~ 5-8% of
feed to protein
 land: need ~ 6-10 sq m / m kcal; 180-310 sq
meter/kg protein
 water: 25-35 gm water/kcal; 700-800 gm/g
protein
© T. M. Whitmore
Opportunities for meat and milk
• Benefits of animal food are the ability to turn
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non-edible stuff into relatively high quality
protein
Improved feeding: fine-tune feeding quantity and
quality to improve efficiencies (as has been done
in US over past 50 yrs)
Major costs/problems are wastes (e.g., a dairy
cow produces 20 tons feces & urine annually)
Can be reused as manure – especially in places
with concentrated industries
But cheap synthetic nitrogen fertilizers and
transport/storage costs etc. make manures less
attractive
© T. M. Whitmore
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Opportunities for meat and milk II
Strategies
Milk: efficiency of milk => a good place to
put efforts
Pigs: since they are 40% of ALL meat
consumed worldwide and are omnivorous and
can gain on many foods (e.g., cassava,
bananas, brans, brewery byproducts, etc.)
Water buffalo: since they are more
efficient converters of roughage to protein
than cows
© T. M. Whitmore
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Opportunities for meat and milk III
Strategies
fishing:
 Yield is poor in open ocean; far better
inshore on continental shelves due to
greater nutrient availability
 As of late 1990s the ocean is fully fished
(no opportunities for expansion, probably
contraction)
© T. M. Whitmore
Opportunities for meat and milk IV
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Strategies
 Aquaculture:
 Now provides about 20% of all fishes; 80% of all
mollusks; ~ 1/5 of all shrimp; 1/3 of all salmon
 Total greater than all mutton and lamb and ~ 1/3
all chicken
 Tilapia is especially attractive: likes warm
climates; is omnivorous; an be raised intensively
or extensively; mild taste
 Has many advantages: improved diets; can be
integrated into agriculture systems (e.g., rice)
 e.g., Chinese carp polyculture system is good: 24 tons/ha (700kg protein) of fish plus other
vegetables etc. on very small farms (0.2-.05 ha)
© T. M. Whitmore
Opportunities for meat and milk V
• Strategies
Aquaculture – problems:
 Humans have less experience raising fish
(especially outside Asia) so predicting
expansion is harder
 More intensive production is possible
 But pollution problems already
© T. M. Whitmore