Transcript Understanding Our Environment

Food and Agriculture
Chapter 11
Outline:
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Nutrition and Food Supplies
Major Food Sources
Soil
 Structure
 Erosion
Agricultural Resources
 Water
 Energy
Genetic Engineering
Sustainable Agriculture
NUTRITION AND FOOD SUPPLIES
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World food supplies have more than kept up
with human population growth over the past
two centuries.
 1950 - 2.5 billion people - average daily
diet was less than 2,000 calories/person.
 2001- 6.0 billion people - world food supply
can provide more than 2,500
calories/person.
Nutrition
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The most common dietary problem in wealthy
countries is over-nutrition.
 In NA and Europe, average daily caloric
intake is 3,500 calories.
Sub-Saharan Africa has not kept food
production up to pace of population growth.
Collapse of Soviet Union also led to significant
collapse in food production.
Chronic Hunger and Food Security
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About 1 in 5 people in the developing world
are considered chronically hungry.
 200 million children
- Can lead to permanently stunted growth,
mental retardation, and other
developmental disorders.
 Poverty is the greatest threat to food
security (The ability to obtain sufficient
food on a daily basis).
Essential Nutrients
Malnutrition - Nutritional imbalance caused by
a lack of specific dietary components such as
protein
Undernourishment – people who can’t get
enough food to meet basic needs
Overnutrition – when food intake esceeds
energy use and causes excess body fat
( Obesity)
Risk of Inadequate Nutrition
Protein Deficiency Diseases
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Kwashiorkor - “Displaced Child” - Occurs
mainly in children whose diet lacks highquality protein.
 Reddish-orange hair, bloated stomach
Marasmus - “To Waste Away” - Caused by a
diet low in both protein and calories.
 Very thin, shriveled
Iron
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Iron deficiency is the most common dietary
imbalance in the world.
 Leads to anemia.
- Increases risk of death from hemorrhage
in childbirth and affects development.
 Red meat, eggs, legumes, and green
vegetables are all good sources of
iron.
Famines
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Famines are characterized by large-scale food
shortages, massive starvation, social
disruption, and economic chaos.
 Mass migrations often occur because
productive capacity has been sacrificed.
 Environmental conditions are immediate
trigger, but politics and economics are often
underlying problems.
- Arbitrary political boundaries block historic
access to refuge areas.
Famines
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Aid policies of rich countries often serve to
distribute surplus commodities and produce
feeling of generosity.
 Food camps have serious drawbacks:
- Stress and crowding
- Lack of sanitation
- Close contact to epidemic diseases
MAJOR FOOD SOURCES
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Three crops deliver majority of world’s
nutrients:
 Wheat, Rice and Corn
- Potatoes, barley, oats and rye are
staples in cool, moist climates.
- Cassava, sweet potatoes, and other
roots and tubers are staples in warm wet
climates.
Producing Food by Green-Revolution
Techniques
 High-input monoculture
 Selectively bred or genetically-engineered
crops
 High inputs of fertilizer
 Extensive use of pesticides
 High inputs of water
 Increased intensity and frequency of
cropping
Green Revolutions
Fig. 13-6 p. 282
First green revolution
Second green revolution
(developed countries)
(developing countries)
Major International agricultural
research centers and seed banks
Figure 13-13 (1)
Page 288
Biodiversity Loss
Loss and degradation of habitat from
clearing grasslands and forests and
draining wetland
Fish kills from pesticide runoff
Killing of wild predators to protect
livestock
Loss of genetic diversity from
replacing thousands of wild crop
strains with a few monoculture strains
Soil
Erosion
Loss of fertility
Salinization
Waterlogging
Desertification
Figure 13-13 (2)
Page 288
Air Pollution
Greenhouse gas emissions from fossil
Fuel issue
Other air pollutants from fossil fuel use
Pollution from pesticide sprays
Water
Aquifer depletion Surface and ground
pollution from pest
Increased runoff andand fertilizers
flooding from land cleared
Overfertilization of
to grow crops
and slow-moving r
from runoff of nitra
Sediment pollution from
phosphates from
erosion
fertilizers, livestoc
wastes, and food
Fish kills from pesticide
Figure 13-13 (3)
Page 288
Human Health
Nitrates in drinking water
Pesticide residues in drinking water,
food, and air
Contamination of drinking and
swimming water with disease organisms
from livestock wastes
Bacterial contamination of meat
Meat and Milk
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Meat and Milk distribution highly inequitable.
 More developed countries make up 20% of
world population, but consume 80% of
meat and milk production.
- 60% of production occurs in lesser
developed countries.
 90% of grain grown in NA is used to feed
livestock.
Meat
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Every 16 kg of grain and soybeans fed to
beef cattle in feedlots produce about 1 kg of
edible beef.
 If we ate the grain directly, we would obtain
twenty-one times more calories and eight
times more protein than we get from eating
the beef.
Figure 13-24
Page 298
Areas
of highest
concentration
Figure 13-25
Page 298
Kilograms of grain needed per kilogram of body weight
Beef cattle
7
Pigs
4
Chicken
2.2
Fish (catfish
or carp)
© 2004 Brooks/Cole – Thomson Learning
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Seafood
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Seafood is an important protein source.
Since 1989, 13/17 major fisheries have
declined or become commercially inviable.
Between 1970-1990, number and average
vessel size of world fishing fleet doubled.
 Now have twice the capacity needed to
extract total annual sustainable harvest.
- Catching $70 billion cost $124 billion.
 1/4 animals considered by-catch.
Seafood
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Seafood is an important protein source.
Since 1989, 13/17 major fisheries have
declined or become commercially inviable.
Between 1970-1990, number and average
vessel size of world fishing fleet doubled.
 Now have twice the capacity needed to
extract total annual sustainable harvest.
- Catching $70 billion cost $124 billion.
 1/4 animals considered by-catch.
Figure 13-30
Page 303
Spotter airplane
Trawler
fishing
Fish farming
in cage
Purse-seine
fishing
trawl flap
sonar
trawl
lines
fish school
trawl bag
Fish caught
by gills
Drift-net fishing
Long line fishing
lines with
hooks
floatbuoy
WAYS WE USE AND ABUSE SOILS
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Approximately 11% of the earth’s land area
is currently in agricultural production.
 Up to four times as much could potentially
be converted to agricultural use.
- Much of this additional land suffers from
constraints.
Land Resources
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In developed countries, 95% of recent
agricultural growth has been from altered
agricultural practices (pesticides - fertilizer).
 Less land cultivated in NA now than 100
years ago.
Many developing countries are reaching limit
of lands that can be exploited for agriculture
without unacceptable social and
environmental costs.
Land Degradation
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Estimated nearly 3 million ha of cropland
ruined annually via erosion, 4 million ha
transformed into deserts, and 8 million ha
converted to non-agricultural uses.
Land Degradation
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Definitions of degradation are based on both
biological productivity and expectations of
what land should be like.
 Generally, land is considered degraded
when soil is impoverished or eroded, runoff is contaminated, or biodiversity is
diminished.
- Water and wind are the driving forces for
vast majority of soil degradation.
OTHER AGRICULTURAL RESOURCES
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Water
 Agriculture accounts for largest single
share of global water use.
- As much as 80% of water withdrawn for
irrigation never reaches intended
destination.
 Cheap cost encourages over-use.
 Waterlogging
 Salinization
Fertilizer
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Lack of nitrogen, potassium, and phosphorus
often limits plant growth.
 Adding nutrients via fertilizer usually
stimulates growth and increases crop yields.
- 1950 - Average of 20 kg/ha fertilizer used.
- 1990 - Average of 91 kg/ha fertilizer used.
 Manure and nitrogen-fixing bacteria are
alternative methods of replenishing soil
nutrients.
Energy
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Farming in industrialized countries is highly
energy-intensive.
 Between 1920-1980, energy use rose
directly with mechanization of agriculture,
and indirectly with spraying of chemicals.
 Altogether, US food system consumes
16% of total energy use.
- Most foods require more energy to
produce, process, and transport than we
yield from them.
NEW CROPS AND GENETIC ENGINEERING
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Most of world food comes from 16 widely
grown crops.
 At least 3,000 species of plants have been
used for food at some point in time.
- Many new or unconventional varieties
might be valuable food supplies.
 Winged-bean
 Triscale
Green Revolution
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Most major improvements in farm production
have come from technological advances and
modification of a few well-known species.
 Corn yields jumped from 25 bushels per
acre to 130 per acre in last century.
- Most of gain accomplished through
conventional plant breeding.
 Also seen rise of dwarf varieties.
Green Revolution - Spread of new varieties
around the world.
Genetic Engineering
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Genetically Modified Organisms (GMO’s)
 Contain DNA possessing genes borrowed
from unrelated species.
- Can produce crops with pest-resistance
and wider tolerance levels.
- Opponents fear traits could spread to
wild varieties, and increased expense
would largely hurt smaller farmers.
 70% of all processed foods in NA contain
transgenic products.
SUSTAINABLE AGRICULTURE
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Soil Conservation
 Managing Topography
- Contour Plowing - Plowing across slope
to slow flow of water.
- Strip Farming - Planting different crops
in alternating strips along land contours.
- Terracing - Shaping land to create level
shelves of earth to hold water and soil.
Soil Conservation
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Providing Ground Cover
 Annual row crops cause highest rates of
erosion because they leave soil bare for
much of the year.
- Leave crop residue after harvest.
- Plant cover crops after harvest.
Soil Conservation
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Reduced Tillage
 Minimum Till - Chisel plow
 Conserv-Till - Coulter (Disc)
 No-Till - Drilling
Often farmers using conservation tillage must
depend relatively heavily on pesticides.
 Traditional tillage helped control weeds
and pests.