1. Food and Agriculture
Chapter 15

2. 15-1: Feeding the World

3. Humans and Nutrition
Famine – the widespread malnutrition and starvation in an area due to a shortage of food, usually caused by a catastrophic event

4. 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.

6. 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

7. Humans and Nutrition Forms of malnutrition Amino acid deficiency
Insufficient variety of food
Low Calorie consumption

8. 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

9. 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

10. Food Efficiency
Yield – the amount of crops produced per unit area

11. 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

12. 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

13. The Green Revolution
Green Revolution – worldwide, between 1950 and 1970, increases in crop yields resulted from the use of new crop varieties

14. 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. 15-2: Crops and Soil

16. 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.

17. 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.

18. 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

19. 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

20. 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.

22. 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

23. 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

24. 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

25. Salinization Salinization – The accumulation of salts in the soil
When water evaporates from irrigated land, salts are left behind

26. 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

27. Pest Control
Pesticide – a poison used to destroy pests, such as insects, rodents, or weeds; examples include insecticides, rodenticides, and herbicides

28. 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.

29. Pest Control
Biological pest control – the use of certain organisms by humans to eliminate or control pests

30. Pest Control Biological pest control aims to:
maintain tolerable pest levels
elevate plant defenses
leave non-species unharmed
the disrupting of insect breeding

31. 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.

32. Engineering a Better Crop
Scientists may use genetic engineering to transfer desirable traits, such as resistance to certain pests, from one organism to another