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Food and Agriculture
Chapter 15
15-1: Feeding the World
Humans and Nutrition
Famine – the widespread malnutrition and starvation in an area due to a shortage of food, usually caused by a catastrophic event
Humans and Nutrition
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. Our bodies need smaller amounts of vitamins and
minerals to remain healthy.
Humans and Nutrition
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
Forms of malnutrition Amino acid deficiency Insufficient variety of food Low Calorie consumption
Sources of Nutrition
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
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
Drought – a prolonged period during which rainfall is below average, and crops grown without irrigation may produce low yields or fail entirely A drought is more likely to cause famine in places
where most food is grown locally
The Green Revolution
Green Revolution – worldwide, between 1950 and 1970, increases in crop yields resulted from the use of new crop varieties
The Green Revolution
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
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
Plows – pushed by the 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
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
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
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 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
No-till farming – a crop is harvested without turning the soil over, as in traditional farming 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
Salinization – The accumulation of salts in the soil When water evaporates from irrigated land, salts
are left behind
Pest Control
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
Pesticide – a poison used to destroy pests, such as insects, rodents, or weeds; examples include insecticides, rodenticides, and herbicides
Pest Control
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
Biological pest control aims to: maintain tolerable pest levels elevate plant defenses leave non-species unharmed the disrupting of insect breeding
Integrated Pest Management
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
Scientists may use genetic engineering to transfer desirable traits, such as resistance to certain pests, from one organism to another