1. Chapter 13 – Agriculture and the Ecology of Food Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. © 2013 Pearson Education, Inc. 13.1 Origins and History of Agriculture Humans began as hunter-gatherers 10,000 years ago humans began to grow food Agriculture System of land management used to grow plants and animals for food, fiber, or energy Originated independently in several regions

3. © 2013 Pearson Education, Inc. 13.1 Origins and History of Agriculture Agriculture began at the end of the last ice age ~10,000 years ago Climate change allowed for cultivation –Longer growing seasons Most believe agriculture arose because of escalating pressure on wild food sources Adaptation of certain organisms led to domestication –Herding animals –Tuber-producing plants

4. © 2013 Pearson Education, Inc. 13.1 Origins and History of Agriculture –Early agriculture used stone tools Development of ceramic and metals led to new tools Supported large communities Technology changed little for 4,000 years –A.D. 1400–1700 brought new crops from the Americas Agronomy –Brings in multiple disciplines to improve agriculture

5. © 2013 Pearson Education, Inc. 13.1 Origins and History of Agriculture –The Green Revolution In the past 50–60 years –Improved plant breeding and techniques –Use of modern fertilizers and pesticides –Agricultural productivity increased many fold

6. © 2013 Pearson Education, Inc. 13.2 Agroecosystems Humans less than 1% of animal biomass We use more than 30% of terrestrial net primary production Converted 1/3 of Earth's ice-free surface to agriculture Agroecosystems –Crops and domesticated animals, the physical environment, and other organisms associated with them.

7. © 2013 Pearson Education, Inc. 13.2 Agroecosystems Energetics Agroecosystems funnel energy into plants and animals useful to humans –Simple food chain Harvest index –Fraction of total production that can be used by humans Domestic animals have poorer trophic-level efficiency than wild animals

8. © 2013 Pearson Education, Inc. 13.2 Agroecosystems Nutrient cycling –Agroecosystems are prone to nutrient loss Harvest –Biomass removed from system Continual disturbance –Soil more vulnerable to erosion Irrigation –Leaching Low biodiversity –Comprised of a few species

9. © 2013 Pearson Education, Inc. 13.3 The Growth of Crop Plants Plants requirements for photosynthesis essential Light Water Essential nutrients –Nitrogen –Phosphorus –Potassium

10. © 2013 Pearson Education, Inc. 13.3 The Growth of Crop Plants Plants selected for storage of carbohydrates, proteins, and oils –Portion of plant we consume tends to be rich in one of these –Leaves Lettuce, spinach, cabbage, onions –Stem Potato, celery, asparagus –Roots Carrots, beets, turnips –Fruits Peppers, apples, squash

11. © 2013 Pearson Education, Inc. 13.3 The Growth of Crop Plants Most agriculture occurs in tropical and temperate zones –Tolerance of temperature and rainfall determine where a crop may be grown –Plants vary in soil needs –Usually matches climate/soil where the crop evolved

12. Major Food Sources Wheat, rice and maize are responsible for the majority of the world's nutrients. Potatoes, barley, oats and rye are staples at high latitudes with cool, moist climates. Potatoes, barley, oats and rye are staples in cool, moist climates. Cassava, sweet potatoes, and other roots and tubers are staples in warm wet climates. Sorghum and millet are drought resistant and staples in dry regions of Africa. Fruits, vegetables and vegetable oils contain high levels of vitamins, minerals, dietary fiber and complex carbohydrates. © 2013 Pearson Education, Inc.

13. 13.3 The Growth of Crop Plants Role of other organisms –Crops are influenced by surrounding organisms Many crops require pollination –Bees and other pollinators Soil organisms recycle nutrients and maintain soil –Worms, insects, bacteria, fungi Pests and pathogens

14. © 2013 Pearson Education, Inc. 13.4 Managing Soil Resources Soil –Mixture of minerals, organic matter, water, air, and organisms Minerals –Sand Particles 0.05-2 mm Chemical structure resembles parent material –Silt Particles 0.002–0.5 mm –Clay Particles less than 0.002 mm

15. © 2013 Pearson Education, Inc. 13.4 Managing Soil Resources Soil horizons –Layers of the soil O horizon Humus–leaves or crop residues A horizon Mixture of organic matter and minerals B horizon Subsoil–rich in clay from sand and silt weathering C horizon Lowest layer Bedrock broken up

16.  Soil Profile - soils  are stratified into  horizontal layers  called soil horizons,  and together they  make up the soil  profile

18. © 2013 Pearson Education, Inc. 13.4 Managing Soil Resources Soil fertility refers to ability of soil to support plant growth Determined by soil characteristics –Availability of nutrients –pH –Amount of aeration –Overall soil structure

19. © 2013 Pearson Education, Inc. 13.4 Managing Soil Resources Soil conservation Agroecosystems lack many of the processes that maintain soil fertility –Accumulation of topsoil Water erosion –Problematic on exposed soil –Cover crops

20. WAYS WE USE & ABUSE SOIL  Much potential cropland suffers from constraints. Approximately 11% of the earth's land area is currently in agricultural production. –Up to four times as much could potentially be converted to agricultural use. Much of this additional land suffers from constraints.

21. Land Resources Cropland per person averages only 0.7 acres worldwide. By 2025, this could decline to 0.42 acres. In developed countries, 95% of recent agricultural growth has come from improved crop varieties or increased fertilization, irrigation, etc. Land conversion involves ecological trade-offs Many developing countries are reaching limit of lands that can be exploited for agriculture without unacceptable social and environmental costs.

22. Areas of Concern for Soil Degradation

23. Erosion: The Nature of the Problem Erosion is an important natural process, resulting in redistribution of the products of geologic weathering, and is part of both soil formation and soil loss. –Tends to begin subtly. Worldwide, erosion reduces crop production by equivalent of 1% of world cropland per year.

24. Mechanisms of Erosion Sheet Erosion - Thin, uniform layer of soil removed. Rill Erosion - Small rivulets of running water gather and cut small channels in the soil. Gully Erosion - Rills enlarge to form channels too large to be removed by normal tillage. Streambank Erosion - Washing away of soil from established stream banks.

25. Mechanisms of Erosion (continued) Wind can equal or exceed water as an erosive force, especially in a dry climate and on flat land. –Intensive farming practices: Row crops leave soil exposed Weed free-fields Removal of windbreaks No crop-rotation or resting periods Continued monocultures

29. © 2013 Pearson Education, Inc. 13.5 Water and Agriculture Water is essential to plant growth –Water availability determined by rainfall and soil factors Amount of water soils hold depends on soil texture and organic matter –Gravitational water Water that flows through soil –Hygroscopic water Water bound to soil particles –Capillary water Water held in micropores

30. © 2013 Pearson Education, Inc. 13.5 Water and Agriculture Irrigation –First used 5,000 years ago –Water diversion and pumping has allowed crops to be grown were water is limited Potential evapotranspiration (PET) –Estimated water evaporated and transpired from a hypothetical agricultural field Even if rainfall exceeds PET, some seasons may experience drought

31. © 2013 Pearson Education, Inc. 13.5 Water and Agriculture Conserving water in agroecosystems Alternative methods –Drip irrigations Plant-breeding programs –Developing new breeds of crops that use less water Planting alternative crops –Jojoba

32. © 2013 Pearson Education, Inc. 13.6 Domestic Animals Domestic animals Significant portion of agriculture 20% Earth's pasture for animals 30% crops for animal feed Trophic-level efficiency varies by species

33. Meat, Milk, and Seafood Milk and meat are highly prized, but their distribution is inequitable. Developed countries make up 20% of world population, but consume 80% of meat and milk production. Less developed countries produce 60% of world's milk and meat. About 90% of the grain grown in North America is used to feed cattle, hogs, poultry, and other animals! Seafood is an important protein source in many countries. This food source is threatened by over- harvesting and habitat destruction.

34. Environmental Issues with Raising Beef Every 16 kg of grain and soybeans fed to beef cattle in feedlots produce 1 kg of edible beef. –If we ate grain directly, we would obtain twenty-one times more calories and eight times more protein than we get eating the beef.

35. © 2013 Pearson Education, Inc. 13.6 Domestic Animals Trophic-level efficiency –Most domestic animals are herbivores –Efficiency depends on ability to break down cellulose –Ungulates most efficient Cattle, sheep, goats, and pigs –Horses have simpler digestive tract A pasture can support twice the number of cattle than horses

36. © 2013 Pearson Education, Inc. 13.6 Domestic Animals Environmental impacts –Waste management Manure is rich in nutrients Some pathogen concern Methane production –Livestock accounts for 5% of global warming –Possible energy source

37. © 2013 Pearson Education, Inc. 13.6 Domestic Animals Environmental impacts Land use –Forests and habitats cleared for grazing Transmission of disease –Coevolution of flu virus –E. coli Impact to human diets

38. © 2013 Pearson Education, Inc. 13.7 Managing Genetic Resources Humans dependent on a handful of crop species Species extremely productive from breeding, hybridization, and cloning Genetic diversity reduced Older varieties have greater genetic diversity –More resistant to change Current efforts to maintain and improve genetic diversity ongoing

39. © 2013 Pearson Education, Inc. 13.7 Managing Genetic Resources Genetically modified organisms (GMOs) –Improve yields –Improve disease and pest resistance Bt corn –Addition of nutrients Golden rice –Controversy still abounds in general public

40. © 2013 Pearson Education, Inc. 13.8 Managing Competitors and Pests Competitors and pests are a major issue –42% of all crops are lost to pests and disease Chemical pest control –Effective, yet some threats to human health Biomagnification –DTT Biological pest control –Use of predators and parasites to control pests

41. Pest Control Biological pests reduce crop yields and spoil as much as half the crops harvested annually. –Estimated up to half current crop yields might be lost in the absence of pesticides. Crops grown without synthetic fertilizers or pesticides tend to have lower yield, but have lower operating costs and less ecological damage.

42. Up to 90% of all pesticides never reach target organisms.

43. © 2013 Pearson Education, Inc. 13.8 Managing Competitors and Pests Agroecosystems management of pests –Managing crop environment can reduce pests –Government regulation reduces pest import –Crop rotation –Mechanical methods for weed/pest control Integrated pest management (IPM) –Uses chemical, biological, and cultural pest control to minimize crop loss

44. © 2013 Pearson Education, Inc. 13.9 The Ecology of Eating Diet determines significant portion of ecological footprint Meat consumption increases footprint Food miles –Distance food traveled before consumption Processing and storage

45. Nutrition and Food Supplies World food supplies: 1950 versus 2000 Richer countries: the most common dietary problem is over-nutrition (obesity) Sub-Saharan Africa: food production has not kept pace with rapid population growth Asia: most rapid increase in crop production and this accompanied rapid population growth  Chronic Hunger and Food Security - within families that don't get enough to eat, women and children have the poorest diets.

46.  Countries at risk for inadequate nutrition  On the left is shown the number and proportion of chronically undernourished people in developing regions. The most hungry people live in East and South Asia. Persistent hunger is a major problem in Africa where the problem is getting worse.

47. Famines are characterized by large-scale food shortages, massive starvation, social disruption, and economic chaos. Some causes are: Environmental conditions - drought, insects, natural disasters National politics - corruption, oppression Armed conflict Economics - price gouging, poverty, landlessness

48. Essential Nutrients Malnourishment - a nutritional imbalance caused by a lack of specific dietary components or an inability to utilize essential nutrients Starchy foods like corn and polished rice tend to be low in several essential nutrients. Protein deficiency diseases - kwashiorkor, marasmus (see next slide). Iron deficiency (anemia) - is the most common dietary deficiency in the world and is most severe in India. Iodine deficiency - causes goiter, hyperthyroidism

49. Protein Deficiency Diseases Kwashiorkor - "Displaced Child" - Occurs mainly in children whose diet lacks high- quality protein. Marasmus - "To Waste Away" - Caused by a diet low in both protein and calories.

50.  Obesity - The most common dietary problem in wealthy countries is over-nutrition.

51. © 2013 Pearson Education, Inc. 13.9 The Ecology of Eating Choices can reduce environmental impacts and encourage sustainable agriculture –Eat more plants –Eat local –Eat fresh foods –Eat seasonally –Choose sustainable products –Ask questions

52. © 2013 Pearson Education, Inc. 13.9 Food for the Future Sustainable agriculture –Aims to provide future generations with high level of food with minimal environmental cost –Must conserve resources and habitat Food distribution –Major obstacle to ending hunger

53. SUSTAINABLE AGRICULTURE Sustainable agriculture (regenerative farming) - goal is to produce food and fiber on a sustainable basis and to repair damage caused by destructive practices. Soil is essential to sustainable agriculture. Soil conservation - land management, ground cover, climate, soil type and tillage system are important elements in soil conservation.

54. Sustainable Agriculture Alternative agricultural practices Integrated Pest Management

55. Ways to Manage Topography Contour - Plowing and planting across (with the contour) slope to slow flow of water (left). Strip-farming - Planting different crops in alternating strips along land contours (left). Terracing - Shaping land to create level shelves of earth again with the slope to hold water and soil (see next slide). Planting perennial (plants that live >2 years) species

56.  Flooded terraces for growing rice in China

57. Providing Ground Cover

58. Providing Ground Cover and Reducing Tillage

59. Methods Used to Reduce Bare Ground Erosion Providing Ground Cover Leave crop residue after harvest. Plant cover crops after harvest. Add protective ground cover such as manure, wood chips, straw, leaves, etc. (mulch). Reduced Tillage –Minimum Till - Chisel plow or ridge-tilling –Conserve-Till - Coulter (Disc) –No-Till - Drilling Often farmers using conservation tillage must depend relatively heavily on pesticides.

60. “Industrialized, chemical-intensive agriculture and our globalized system of distributing food and fiber are literally destroying the earth, driving two billion farmers off the land, and producing a product which is increasingly contaminated. That’s why the wave of the future is organic and sustainable, not GMO.” Ronnie Cummins, Organic Consumers Association