Transcript Understanding Our Environment

Food and Agriculture
Chapter 11
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Outline:
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Nutrition and Food Supplies
Major Food Sources
Soil
 Structure
 Erosion
Agricultural Resources
 Water
 Energy
Genetic Engineering
Sustainable Agriculture
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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).
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Essential Nutrients
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Malnourishment - Nutritional imbalance
caused by a lack of specific dietary
components.
 In poorer countries, people often cannot
afford to purchase an adequate variety of
foods, including meats and vegetables.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Risk of Inadequate Nutrition
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
SOIL: A RENEWABLE RESOURCE
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Soil - A complex mixture of weathered
minerals, partially decomposed organic
materials, and a host of living organisms.
 At least 20,000 different soil types in the US.
- Vary due to influences of parent material,
time, topography, climate, and organisms.
 Can be replenished and renewed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Soil Composition
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Particle size affects soil characteristics.
 Spaces between sand particles give sandy
soil good drainage and allow aeration.
- Can easily dry out.
 Tight packing of small particles in silty or
clay soils makes them less permeable to
air and water.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Soil Structure
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Soil exhibits wide range of organic content.
 Humus - Insoluble residue from partially
decomposed plants and animals.
- Most significant factor in soil structure.
Activity of organisms living in soil helps
create structure, fertility, and cultivation
suitability.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Soil Profiles
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Soils are stratified into horizontal layers
called soil horizons.
 Together make up soil profile.
- O Horizon (Organic layer)
 Leaf litter, partially decomposed
organisms.
- A Horizon (Topsoil)
 Mineral particles mixed with organic
material.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Soil Profiles
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E Horizon (Leached)
 Depleted of soluble nutrients.
B Horizon (Subsoil)
 Often dense texture from
accumulating nutrients.
C Horizon (Parent Material)
 Weathered rock fragments with little
organic material.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Soil Types
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Soils are classified according to structure
and composition (12 Orders):
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Mollisols
Alfisols
Spodosols
Oxisols
Ultisols
Aridosols
Andiosols
Vertisols
Histosols
Inceptisols
Entisols
Gelisols
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Soil Degradation
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Erosion
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Erosion is an important natural process,
resulting in redistribution of the products of
geologic weathering, and is part of both soil
formation and soil loss.
 Tends to begin subtly.
- Worldwide, erosion reduces crop
production by equivalent of 1% of world
cropland per year.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Mechanisms of Erosion
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Rill Erosion - Small rivulets of running water
gather together and cut small channels in the
soil.
Gully Erosion - Rills enlarge to form bigger
channels too large to be removed by normal
tillage.
Streambank Erosion - Washing away of soil
from established streambanks.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Mechanisms of Erosion
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Wind can equal or exceed water as an
erosive force, especially in a dry climate and
on flat land.
 Intensive farming practices:
- Row crops leave soil exposed
- Weed free-fields
- Removal of windbreaks
- No crop-rotation or resting periods
- Continued monocultures
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Summary:
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Nutrition and Food Supplies
Major Food Sources
Soil
 Structure
 Erosion
Agricultural Resources
 Water
 Energy
Genetic Engineering
Sustainable Agriculture
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.