Transcript Food - walker2014

Food and Agriculture
Chapter 15
15-1: Feeding the World
Humans and Nutrition
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Famine – the widespread malnutrition and
starvation in an area due to a shortage of
food, usually caused by a catastrophic event
Humans and Nutrition
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The amount of energy that is available in food
is expressed in Calories.
The major nutrients we get from food are
carbohydrates, proteins, and lipids.
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Our bodies need smaller amounts of vitamins and
minerals to remain healthy.
Humans and Nutrition
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Malnutrition – a disorder of nutrition that
results when a person does not consume
enough of each of the nutrients that are
needed by the human body
Humans and Nutrition
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Forms of malnutrition
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Amino acid deficiency
Insufficient variety of food
Low Calorie consumption
Sources of Nutrition
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Diet – the type and amount of food that a
person eats
The foods produced in the greatest amounts
worldwide are grains, plants of the grass
family whose seeds are rich in carbohydrates
Diets Around the World

People worldwide generally consume the
same major nutrients and eat the same basic
kinds of food, but diets vary by region
Food Efficiency
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Yield – the amount of crops produced per unit
area
World Food Problems

World food production has been increasing
for decades, but now food production is not
increasing as fast as the human population is
increasing
Droughts and Famines
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Drought – a prolonged period during which
rainfall is below average, and crops grown
without irrigation may produce low yields or
fail entirely
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A drought is more likely to cause famine in places
where most food is grown locally
The Green Revolution
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Green Revolution – worldwide, between 1950
and 1970, increases in crop yields resulted
from the use of new crop varieties
The Green Revolution
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As a result of the overuse of fertilizers and
pesticides, yields from green revolution crops
are falling

Chemicals required by new crop varieties can
degrade the soil if they are not used properly
15-2: Crops and Soil
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Arable land – farmland that can be used to
grow crops
But, as the human population continues to
grow, the amount of arable land per person
decreases.
Agriculture: Traditional
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Plows – equipment that’s pushed by farmers
or pulled by livestock
Organic fertilizers, such as manure, are used
to enrich soil while fields are irrigated by
water flowing through ditches.
Agriculture: Modern
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Synthetic chemical fertilizers have replaced
manure and plant wastes to fertilize soil.
A variety of overhead sprinklers and drip
systems may be used for irrigation
Fertile Soil: The Living Earth
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Topsoil – the surface layer of the soil, which
is usually richer in organic matter than the
subsoil is
Fertile topsoil is composed of living
organisms, rock particles, water, air, and
organic matter
Fertile Soil: The Living Earth
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Several layers of soil lie under the topsoil.
The bottom layer is bedrock, which is the
solid rock from which most soil originally
forms.
Soil Erosion: A Global Problem
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Erosion – a process in which the materials of
the Earth’s surface are loosened and
transported by wind, water, ice, or gravity
Land Degradation

Desertification – the process by which human
activities or climatic changes make arid or
semiarid areas more desertlike

Example: Crops are planted too frequently and
fallow periods (land that remain unplanted) are
being shortened
Soil Conservation
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No-till farming – a crop is harvested without
turning the soil over, as in traditional farming
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The seeds of the next crop are planted among the
remains of the previous crop.
Although this method saves time and reduces soil
erosion, it is not suited for all crops
Salinization
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Salinization – The accumulation of salts in
the soil
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When water evaporates from irrigated land, salts
are left behind
Pest Control
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Pest – any organism that occurs where it is
not wanted or that occurs in large enough
numbers to cause economic damage
Worldwide, pests destroy about one-third of
the world’s potential food harvest
Pest Control
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Pesticide – a poison used to destroy pests,
such as insects, rodents, or weeds; examples
include insecticides, rodenticides, and
herbicides
Pest Control
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Over time, spraying large amounts of
pesticide to get rid of pests usually makes the
pest problem worse.
Pest populations may evolve resistance, the
ability to survive exposure to a particular
pesticide.
Pest Control

Biological pest control – the use of certain
organisms by humans to eliminate or control
pests
Pest Control
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Biological pest control aims to:
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maintain tolerable pest levels
elevate plant defenses
leave non-species unharmed
the disrupting of insect breeding
Integrated Pest Management
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The goal of integrated pest management is
not to eliminate pest populations but to
reduce pest damage to a level that causes
minimal economic damage.
Engineering a Better Crop
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Scientists may use genetic engineering to
transfer desirable traits, such as resistance to
certain pests, from one organism to another