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