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Chapter 11
Producing Enough Food for
the World
How we feed the world
• Farming degrades soil
• Fertilizers & pesticides affect soil, water &
downstream ecosystems
• 11% of total land area of the world is
agriculture – a human induced biome
(30% Europe 6% Australia)
– If human population doubles ---- agriculture
must double & water needed is doubled.
How we starve
• Undernourishment – lack of sufficient
calories in available food.Manifested in
famines that are fast acting
– Problems with undernourishment:
• Marasmus: progressive emaciation due to lack of
protein & calories
• Kwashiorkor: lack of sufficient protein in infants –
failure of neural development
• Chronic hunger: enough food to stay alive, but not
enough to live a productive & satisfactory life
How we starve
• Malnourishment – lack of specific chemical
components of foods ie: proteins, vitamins,
etc. - Long term
• Africa – the continent with the most acure
food shortages due to weather & strife
• Food distribution fails because:
– Poor cannot pay for food and/or delivery
– Transportation is lacking and too expensive
– Food is withheld for political & military
purposes
Food Aid
• Food aid is a short term answer
• Must solve the problem of food distribution
and increase local production
– ie: long term sustainable agriculture - locally
What we eat & grow
• 500,000 plant species
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3000 used as agricultural crops
150 cultivated on a large scale
(200) species grown in the United States
14 species provide for most of the worlds food
o In order of importance:
o Wheat
o Rice
o Corn (maize)
o Potatoes
sweet potatoes
manioc
sugar cane
sugar beet
What we eat & grow
• Forage: food grown for animals (alfalfa,
sorghum, grasses)
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Chickens
14 billion
Cattle
1.3 billion
Sheep
1 billion
Ducks
less than 1 billion
Pigs
1 billion
Goats
700 million
Buffalo
160 million
Camels
18 million
IMPORTANT FOOD SOURCES – HAVE A MAJOR IMPACT ON
LAND
Crops
Rangeland:
Provides food for grazing and browsing
animals without plowing and planting
Pasture:
Plowed, planted and harvested to provide
forage for animals
Aquaculture
• Aquaculture
– The farming of food in aquatic habitats
– Carp, tilapia, oyster, shrimp
– China has been doing this – traced back to 475 BC
• Mariculture
– The farming of ocean fish
Six Ways Agroecosystems Differ
from Natural Ecosystems
1. Try to stop ecological succession and keep the
agroecosystem in an early successional state
2. Monoculture: Large areas planted with a single
species (entire crop vulnerable to disease, depletes soil of
specific chemicals)
3. Crops are planted in neat rows – no hiding from pests
or blending in
4. Farming greatly simplifies biological diversity &
food chains
5. Plowing is unlike any natural soil disturbance –
increases erosion and decreases organic matter
6. Genetic modification of crops.
Limiting factors
• Limiting Factor: The single requirement for growth
available in the least supply in comparison to the need of
an organism
High quality agricultural soil :
– All chemicals required for plant growth
– Physical structure that lets air & water move freely
through soil
– Retains water well
– High organic content
– Mixture of sediment particle sizes
• Different crops require different soil contents, so…
rarely does a soil have everything needed. Usually
ONE factor is limiting
Liebig’s Law of the Minimum
• The growth of a plant is affected by one
limiting factor at a time – the one whose
availability is the least in comparison to the
needs of the plant.
• The idea that some single factor determines the
growth, and therefore, the presence of a species.
Limiting Factors
2 Types of Life-Important Chemicals
1. Macronutirents – required by all living things in
relatively large amounts:
S, P, Mg, Ca, K, N, O, C, H
2. Micronutirents – chemical element required in
small amounts, wither in extremely small amounts
by all life forms or in moderate amounts for some
forms of life:
Cu, Zn, Mn, Fe, Molybdenum
Elements can be in short supply or there may be too much !!
The older the soil, the more it is likely to lack trace elements
because of leaching by water
History of Agriculture
• Organic agriculture introduced 10,000 yrs.
Ago.
• 18th & 19th centuries (industrial revolution)shift to mechanized or demand based
agriculture
• 20th century- return to resouce based
agriculture
• Today – growing interest in organic
agriculture & use of genetically engineered
crops
Types of agriculture
• Mechanized Agriculture:
– Production is determined and limited by
economic demand –
• NOT by resources
Resource Based Agriculture
• Production limited by environmental
sustainability and available resources
• Economic demand exceeds production
Organic Farming
• More like natural ecosystem
• Minimizes negative environmental impact
• Food does not contain artificial compounds
12,000 farmers in US - growing 12% per year
Increasing the Yield per Acre
1. The Green Revolution
- Programs that have led to the development of new strains
of crops with higher yields, better resistance to disease or
better ability to grow under poor conditions
- Ex: hybridized rice (increased yield)
- Maize (disease resistant)
2. Improved Irrigation
expensive and found in developed countries
Genetically Modified Food
• Genetically Modified Crops are modified by
genetic engineers to produce higher crop
yields and increase resistance to drought,
cold, heat, toxins, plant pests and disease.
GMF’s
• High yields
• Nitrogen fixing – reduces need for
fertilizers
• Drought tolerant (also: cold, heat and toxic
element tolerant)
– ¾ soybeans, 1/3 corn and more than ½ of the
plants used to produce canola oil are GMF