Transcript Diapositive 1 - yayscienceclass

Unit 07
Food & Agriculture
Chapter 11
Producing Enough Food for the World
Who cares about food and agriculture?
Today:
• 2 billion people lack reliable
access to food
• 800 million people today
are chronically malnourished
• 300 million of these are
children
Percents indicate the
percent of people in each
location that are
undernourished.
Quality of Food
Malnourishment
One in three people has
a deficiency of one or
more vitamins and
minerals, especially
vitamin A, iodine (causes
goiter - enlargement of
thyroid gland), and iron.
• A micronutrient disorder
Figure 13-2
War and the Environment
Undernourishment
Starving children
collecting ants to eat
in famine-stricken
Sudan, Africa which
has been involved in
civil war since 1983.
Figure 13-3
Kwashiorkor
In the Ga language of Ghana, kwashiorkor means
"the sickness of the child who is displaced from the breast”
or “the disease of the displaced child"
The photograph above
shows Sudanese children
with severely swollen
abdomens, a characteristic
symptom of kwashiorkor
Kwashiorkor is an ailment that results
from severe protein deficiency. It is
mainly seen in the tropical and
subtropical regions of west and
central Africa. It commonly occurs
when a child is weaned onto a diet
deficient in protein after the birth of
another child.
• A macronutrient disorder
Daily Intake of Calories
Worldwide
Eating Too Much
Overnutrition
• Overnutrition and lack of exercise
can lead to reduced life quality,
poor health, and premature death.
• A 2005 Boston University study found that
about 60% of American adults are overweight
and 33% are obese (totaling 93%).
• Americans spend $42 billion per year
trying to lose weight.
• $24 billion per year is needed to
• eliminate world hunger.
Population and Income Growth
will Fuel Increased Food Demand
Increased food demand matrix
High
61%
88%
147%
Projection
(75%)
Caloric
shift
to meat
products
Medium
Low
51%
76%
Base Case
Demand +75%
• Population growth
+45%
100%
• Increased meat
consumption +30%
• Shift to “healthy” and
specialized foods
39%
Low
61%
88%
Medium
Population X income growth
Source: IFPRI, FAO
Year 2020
High
•In India, the gains
from the “Green
Revolution” are
getting saturated
Food Production
• Food production from croplands,
rangelands, ocean fisheries,
and aquaculture has increased dramatically.
• Wheat, rice, and corn provide more than half
of the world’s consumed calories.
– Fish and shellfish are an important source of food
for about 1 billion people mostly in Asia and in
coastal areas of developing countries.
Industrial Food Production:
High Input Monocultures
• About 80% of the world’s food supply
is produced by industrialized agriculture.
– Uses large amounts of fossil fuel energy, water,
commercial fertilizers, and pesticides to produce
monocultures.
– Greenhouses are increasingly being used.
– Plantations are being used in tropics for cash
crops such as coffee, sugarcane, bananas.
Locations of
the world’s
principal types
of food
production.
Industrialized agriculture
Plantation agriculture
Intensive traditional ag.
Shifting cultivation
Nomadic herding
No agriculture
World Land Use
Crops
Rangeland:
Provides food for grazing and browsing
animals without plowing and planting
Pasture:
Plowed, planted and harvested to
provide forage for animals
Geographic Distribution of World
Production of a Few MAJOR
Small-grain Crops
World Small Grain Production
Aquaculture
• Aquaculture
– The farming of food in aquatic habitats
• Mariculture
– The farming of ocean fish
Vietnamese fishery.
Site of mollusk cultivation in eastern Canada
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
3. Crops are planted in neat rows
4. Farming greatly simplifies biological diversity
5. Plowing is unlike any natural soil disturbance
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
2 Types of Life-Important Chemicals
1. Macronutirents
2. Micronutirents
Synergistic Effects: a change in availability of one
resource affects the response of an organism to
some other resource
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
2. Improved Irrigation
Organic Farming
3 Qualities
1. It is more like natural ecosystems than
monocultures
2. It minimizes negative environmental impacts
3. The food that results from it does not contain
artificial compounds
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.
Chapter 12
Effects of Agriculture on the Environment
Many environmental problems
result from agriculture:
• Soil erosion
• Sediment transport and
deposition downstream
• On-site pollution from
fertilizers and pesticides
• Deforestation
• Desertification
• Degradation of water
aquifers
• Salinization
• Accumulation of toxic
metals and organic
compounds
• Loss of biodiversity
ROTECTING FOOD RESOURCES: PEST
MANAGEMENT
Organisms found in
nature (such as
spiders) control
populations of most
pest species as part
of the earth’s free
ecological services.
Figure 13-27
ROTECTING FOOD RESOURCES: PEST
MANAGEMENT
• We use chemicals to repel or kill pest
organisms as plants have done for millions of
years.
• Chemists have developed hundreds of
chemicals (pesticides) that can kill or repel
pests.
– Pesticides vary in their persistence.
– Each year > 250,000 people in the U.S. become ill
from household pesticides.
PROTECTING FOOD RESOURCES: PEST
MANAGEMENT
• Advantages and disadvantages of conventional
chemical pesticides.
Figure 13-28
Individuals Matter:
Rachel Carson
• Wrote Silent Spring
which introduced
the U.S. to the
dangers of the
pesticide DDT and
related compounds
to the environment.
Figure 13-A
The ideal Pesticide and the
Nightmare Insect Pest
• The ideal pest-killing chemical has these
qualities:
– Kill only target pest.
– Not cause genetic resistance in the target
organism.
– Disappear or break down into harmless chemicals
after doing its job.
– Be more cost-effective than doing nothing.
Superpests
• Superpests are
resistant to pesticides.
• Superpests like the
silver whitefly (left)
challenge farmers as
they cause > $200
million per year in U.S.
crop losses.
Figure 13-29
Pesticide Protection Laws in
the U.S.
• Government regulation has banned
a number of harmful pesticides but some
scientists call for strengthening pesticide laws.
– The Environmental Protection Agency (EPA), the
Department of Agriculture (USDA), and the Food
and Drug Administration (FDA) regulate the sales
of pesticides under the Federal Insecticide,
Fungicide and Rodenticide Act (FIFRA).
– The EPA has only evaluated the health effects of
10% of the active ingredients of all pesticides.
Other Ways to Control Pests
• Genetic
engineering can
be used to
develop pest and
disease resistant
crop strains.
Both tomato plants were exposed to destructive
caterpillars. The genetically altered plant (right)
shows little damage.
Figure 13-32
Case Study
Integrated Pest Management:
A Component of Sustainable
Agriculture
• An ecological approach to pest control uses a
mix of cultivation and biological methods, and
small amounts of selected chemical pesticides
as a last resort.
– Integrated Pest Management (IPM)
Case Study
Integrated Pest Management:
A Component of Sustainable
Agriculture
• Many scientists urge the USDA to use three
strategies to promote IPM in the U.S.:
– Add a 2% sales tax on pesticides.
– Establish federally supported IPM demonstration
project for farmers.
– Train USDA personnel and county farm agents in
IPM.
• The pesticide industry opposes such
measures.
Biological Pest Control
Integrated Pest Management
– Control of agricultural pests using several methods
together, including biological and chemical agents
– Goals:
• To minimize the use of artificial chemicals
• To prevent or slow the buildup of resistance by pests to
chemical pesticides
What Can You Do?
Reducing Exposure to Pesticides
• Grow some of your food using organic methods.
• Buy organic food.
• Wash and scrub all fresh fruits, vegetables, and wild foods you pick.
• Eat less or no meat.
• Trim the fat from meat.
Fig. 13-30, p. 299
Soil
Soil Formation: Soil is formed slowly as rock
(the parent material) erodes into tiny
pieces near the Earth's surface.
Organic matter decays and mixes with
inorganic material (rock particles, minerals and
water) to form soil.
Soil Horizons (layers): Soil is made up of distinct
horizontal layers; these layers are called horizons.
They range from rich, organic upper layers (humus
and topsoil) to underlying rocky layers ( subsoil,
regolith and bedrock).
Humus
• The main contributor to the fertility of the soil.
It originates from decomposing material.
• Found on the SURFACE of the soil
• So for examples one reason why grasslands are
considered the “bread baskets of the world is
because of their great fertility due in large part to the natural humus
which accumulates because grasses form a large amount of organic matter
that decomposes.
• Tropical rainforests, however, DO NOT have a large amount of humus
because the decomposition rate there is so fast the nutrients are almost
immediately reabsorbed by plants. This is why the tropical rainforest does
not yield fertile soil when it is cut down.
• Some forests do have humus, however, deciduous forests accumulate
humus because of the decomposition of plants and animals. Temperate
rainforests also contain humus because needles and leaves will
decompose.
• Importance: nutrients (fertility), holds water, improves soil aeration,
prevents erosion, improves habitats for soil living organisms, improves soil
structure, allows roots to grow more easily.
O Horizon - The top, organic layer of soil, made up
mostly of leaf litter and humus (decomposed organic
matter).
A Horizon - The layer called topsoil; it is found below
the O horizon and above the E horizon. Seeds
germinate and plant roots grow in this dark-colored
layer. It is made up of humus (decomposed organic
matter) mixed with mineral particles.
E Horizon - This eluviation (leaching) layer is light in
color; this layer is beneath the A Horizon and above the
B Horizon. It is made up mostly of sand and silt, having
lost most of its minerals and clay as water drips
through the soil (in the process of eluviation).
B Horizon - Also called the subsoil - this layer is
beneath the E Horizon and above the C Horizon. It
contains clay and mineral deposits (like iron, aluminum
oxides, and calcium carbonate) that it receives from
layers above it when mineralized water drips from the
soil above.
C Horizon - Also called regolith: the layer beneath the
B Horizon and above the R Horizon. It consists of
slightly broken-up bedrock. Plant roots do not penetrate
into this layer; very little organic material is found in this
layer.
R Horizon - The unweathered rock (bedrock) layer that
is beneath all the other layers.
Testing Soil
• Chemical
–
–
–
–
pH
salinity
organic content (measuring humus)
Testing for major elements such as N, P, K, S or trace
elements such as Co, B, Ca, Mg etc.
• Physical
– Soil Texture
– Porosity – how much water the soul can old due to the
amount of air/space available
– Moisture content
Global Outlook: Soil Erosion
• Soil is eroding faster than it is forming on more
than one-third of the world’s cropland.
Figure 13-10
Where Eroded Soil Goes:
Sediments Also Cause Environmental Problems
Ways to slow erosion:
• Making Soil Sustainable
• Contour Plowing
• No-Till Agriculture
– Combination of farming practices that include not
plowing the land and using herbicides to keep
down weeds.
Desertification
of arid and semi-arid lands
Moderate
Severe
Very severe
Case Study: Soil Erosion in the U.S.
Some Hopeful Signs
• Soil erodes faster than it forms on most U.S.
cropland, but since 1985, has been cut by
about 40%.
– 1985 Food Security Act (Farm Act): farmers
receive a subsidy for taking highly erodible land
out of production and replanting it with soil saving
plants for 10-15 years.
Desertification
• Desertification is the deterioration of land in
arid, semi- arid and dry sub humid areas due
to changes in climate and human activities
• Can be caused by
– Poor farming practices
– Conversion of marginal grazing lands to croplands
Desertification:
Degrading Drylands
About one-third of the world’s land has lost
some of its productivity because of drought and
human activities that reduce or degrade topsoil.
Figure 13-12
Carrying Capacity of US
Pasture & Rangelands
Average number of cows per square kilometer
•Bad farming
practices have
lead to an
increase in
desertification in
the US.
•Climate suggests
that 1/3 of the
earth should be
deserts, however
now deserts cover
nearly 50% of the
planet because of
human action!
Salinization and Waterlogging
Repeated
irrigation can
reduce crop
yields by
causing salt
buildup in the
soil and
waterlogging of
crop plants.
Figure 13-13
Solutions
Soil Salinization
Prevention
Cleanup
Reduce irrigation
Flush soil
(expensive and
wastes water)
Stop growing crops
for 2–5 years
Switch to salttolerant crops
(such as barley,
cotton,
sugarbeet)
Install underground
drainage systems
(expensive)
Fig. 13-15, p. 281
Salinization and Waterlogging of
Soils: A Downside of Irrigation
• Example of high
evaporation,
poor drainage,
and severe
salinization.
• White alkaline
salts have
displaced cops.
Figure 13-14
SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
Modern farm machinery can plant
crops without disturbing soil
(no-till and minimum tillage.
– Conservation-tillage farming:
•
•
•
•
•
Increases crop yield.
Raises soil carbon content.
Lowers water use.
Lowers pesticides.
Uses less tractor fuel.
SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
Terracing, contour
planting, strip
cropping, alley
cropping, and
windbreaks can
reduce soil erosion.
Figure 13-16
SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
• Fertilizers can help restore soil nutrients, but
runoff of inorganic fertilizers can cause water
pollution.
– Organic fertilizers: from plant and animal (fresh,
manure, or compost) materials.
– Commercial inorganic fertilizers: Active
ingredients contain nitrogen, phosphorous, and
potassium and other trace nutrients.
THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
• Since 1950, high-input agriculture has produced
more crops per unit of land.
• In 1967, fast growing dwarf varieties of rice and
wheat were developed for tropics and subtropics.
THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
• Lack of water, high costs for small
farmers, and physical limits to increasing crop
yields hinder expansion of the green revolution.
• Since 1978 the amount of irrigated land per
person has declined due to:
– Depletion of underground water supplies.
– Inefficient irrigation methods.
– Salt build-up.
– Cost of irrigating crops.
THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
• Modern agriculture has a greater
harmful environmental impact than
any human activity.
• Loss of a variety of genetically different crop and
livestock strains might limit raw material needed
for future green and gene revolutions.
– In the U.S., 97% of the food plant varieties available in
the 1940 no longer exist in large quantities.
Biodiversity Loss
Soil
Water
Air Pollution
Human Health
Nitrates in
drinking water
Loss and
degradation of
grasslands,
forests, and
wetlands
Erosion
Water waste
Loss of fertility
Aquifer depletion
Greenhouse gas
emissions from
fossil fuel use
Salinization
Increased runoff and
flooding from cleared
land
Pesticide residues
Other air pollutants in drinking water,
from fossil fuel use food, and air
Fish kills from
pesticide runoff
Desertification
Waterlogging
Killing wild predators to
protect livestock
Loss of genetic diversity of
wild crop strains replaced
by monoculture strains
Sediment pollution from
erosion
Fish kills from pesticide
runoff
Greenhouse gas
emissions of
nitrous oxide from
use of inorganic
fertilizers
Surface and groundwater
pollution from pesticides
and fertilizers
Belching of the
greenhouse gas
Overfertilization of
methane by cattle
lakes and rivers from
runoff of fertilizers,
livestock wastes, and
Pollution from
food processing wastes pesticide sprays
Contamination of
drinking and
swimming water
with disease
organisms from
livestock wastes
Bacterial
contamination of
meat
Fig. 13-18, p. 285
THE GENE REVOLUTION
• To increase crop yields, we can
mix the genes of similar types of
organisms and mix the genes of
different organisms.
– Artificial selection has been used for centuries to
develop genetically improved varieties of crops.
– Genetic engineering develops improved strains at
an exponential pace compared to artificial
selection.
• Controversy has arisen over the use of
genetically modified food (GMF).
The Terminator Gene
• A genetically modified crop which has a gene
to cause the plant to become sterile after the
first year
Grazing on Rangelands
• Overgrazing occurs when the carrying
capacity is exceeded. It can cause severe
damage to lands
• It is important to properly manage
livestock, including using appropriate lands
for gazing and keeping livestock at a
sustainable density
SOLUTIONS: SUSTAINABLE
AGRICULTURE
• Three main ways to reduce hunger and
malnutrition and the harmful effects of
agriculture:
– Slow population growth.
– Sharply reduce poverty.
– Develop and phase in systems of more
sustainable, low input agriculture over the next
few decades.
Solutions
Sustainable Organic Agriculture
More
High-yield
polyculture
Organic fertilizers
Biological pest
control
Integrated pest
management
Efficient
irrigation
Perennial crops
Crop rotation
Water-efficient
crops
Soil conservation
Subsidies for
sustainable farming
and fishing
Less
Soil erosion
Soil salinization
Aquifer depletion
Overgrazing
Overfishing
Loss of
biodiversity
Loss of prime
cropland
Food waste
Subsidies for
unsustainable
farming and
fishing
Population
growth
Poverty
Fig. 13-33, p. 302
Sustainable
Agriculture
Results of 22 year
study comparing
organic and
conventional
farming.
Figure 13-34
What Can You Do?
Sustainable Organic Agriculture
• Waste less food
• Eat less or no meat
• Feed pets balanced grain foods instead of meat
• Use organic farming to grow some of your food
• Buy organic food
• Eat locally grown food
• Compost food wastes