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Chapter 14: Food & Soil Resources

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1 Chapter 14: Food & Soil Resources

2 The three systems humans depend on for their food supply
Croplands (77%) – land used for planting crops; vegetables, fruits, and grains Rangelands (16%)- Land used for grazing livestock; meat products Ocean fisheries (7%) - shellfish/fish (6% of protein in human diet)

3 High-Tech Gear & Electronics Fertilizers Pesticides
Human Food Supply Fisheries Croplands Rangelands Major increase in food production post-1950 Tractors Farm Equip. Feedlots Feed Pens High-Tech Gear & Electronics i n p u t Irrigation Growth Hormones Aquaculture Fertilizers Pesticides Careful Breeding

4 Human Population Growth and Food Production
9 billion humans by 2054 More food than has been produced in last 10k yrs Is current technology capable? Environmental degradation? Pollution Water supply (irrigation) Overgrazing Overfishing Ecological services (matter; energy)

5 Lack of Diversity in Food
30,000 edible plant species 3 grain crops that provide “more than ½ of the calories people consume”. But 90% of all food only comes from 15 plants [esp. wheat, rice, corn] and 8 animals- [esp. beef, pork, chicken] Fish- 1% energy 6 % protein

6 Major Types of Agriculture
Traditional subsistence (20%, 44% pop.) Low-input, human labor, "just enough" Shifting cultivation; nomadic livestock Traditional intensive Higher input, "more than enough" Plantation Monoculture cash crops (bananas, coffee, sugarcane, etc) Industrialized (high-input) 25% of all cropland, developed nations

7 Industrialized agriculture
Shifting cultivation Plantation agriculture Nomadic herding Intensive traditional agriculture No agriculture Fig. 12.2, p. 263

8 The Green Revolution increased production of food per unit of area of cropland; planting monocultures, increase use of pesticides, water, fertilizers, etc. Since 1950 Develop & plant monocultures (ie. corn) Input fertilizer, pesticides, water Multiple cropping on plot of land Since 1967 Fast growing dwarf varieties of rice and wheat More food on less land Increase use of fossil fuels, fertilizers, pesticides, irrigation Age of Genetic Engineering >2/3 of products on U.S. grocery store shelves contain ingredients from GE crops!

9 Green-Revolution- increasing global food production…
Farm more land = Increase crop yield / land area High-yield monocultures = selective breeding genetic engineering (GMO’s) High Input = high energy input (8% world oil) fertilizers, pesticides, water High intensity frequency of cropping = dwarf varieties- 3-5x yield multicropping (2-3/year)

10 Wheat monoculture in Washington
Monocultures Intensified agriculture meant monocultures, vast spreads of a single crop. This is economically efficient, but increases risk of catastrophic failure (“all eggs in one basket”). Wheat monoculture in Washington Figure 9.4a

11 Green revolution: Environmental impacts
Intensification of agriculture causes environmental harm: Pollution from synthetic fertilizers Pollution from synthetic pesticides Water depleted for irrigation Fossil fuels used for heavy equipment However, without the green revolution, much more land would have been converted for agriculture, destroying forests, wetlands, and other ecosystems.

12 First green revolution (developed countries) Second green revolution
(developing countries) Major International agricultural research centers and seed banks

13 Energy Use in Food Production: Industrial Agriculture (United States)
Since1940’s: 2x production on the same amount of land Agribusiness- big companies and large family farms own 75% of US food production - 2% pop.= farmers; 9% pop.= involve in production - Agriculture provides18% US GNP; 19% jobs (private sect); 0.3% world's labor - 17% of world’s grain is produced in the US; ½ the world’s corn & soybean exports Putting food on the table utilizes 17% of US commercial energy, mostly from oil Food production uses 3 units of fossil fuel energy for 1 unit of food energy obtained. Units of energy take in to account the energy used to grow, store, process, pack, process, refrigerate, and cook Plants involve > energy out than in; Livestock involve > energy in, than out.

14 Energy Use in Food Production: Traditional and Traditional Intensive
20% of world food on 75% cultivated land Most traditional farmers use INTERPLANTING - growing several crops on a single plot of land. Types of interplanting- Polyvarietals - varieties of 1 crop Intercropping - 2+ different on same plot (legumes/grain) Agroforestry/alley cropping - crops/trees together Polyculture - many plants maturing at different times on same plot Advantages include: < energy input, erosion/weather protection, pest/herbicides not needed

15 Intercropping Polyculture Polyvarietals Agroforestry

16 Soil Erosion and Degradation
Causes: water, wind, and people Land degradation- when natural or human induced processes reduce the future ability of land to support crops, livestock or wild species. (i.e. soil erosion due to flowing water or wind) Erosion of topsoil leads to loss of soil fertility and increase sediment in nearby surface waters which can block sunlight, kill fish, and clog irrigation ditches, channels, etc.

17 Causes of soil degradation
Most soil degradation is caused by: • livestock overgrazing • deforestation • cropland agriculture Figure 8.2

18 Types of soil erosion Rill erosion Splash erosion Gully erosion
Sheet erosion Figure 8.11

19 Desertification A loss of more than 10% productivity due to:
• Erosion • Soil compaction • Forest removal • Overgrazing • Drought • Salinization • Climate change • Depletion of water resources When severe, there is expansion of desert areas, or creation of new ones, e.g., the Middle East, formerly, “Fertile Crescent”.


21 The Dust Bowl Drought and degraded farmland produced the 1930s Dust Bowl. Storms brought dust from the U.S. Great Plains all the way to New York and Washington, and wrecked many lives. Figure 8.14

22 Desertification Causes Consequences Worsening drought Famine
Economic losses Lower living standards Environmental refugees Overgrazing Deforestation Erosion Salinization Soil compaction Natural climate change

23 Preventing soil degradation
Several farming strategies to prevent soil degradation: • Crop rotation • Contour farming • Intercropping • Terracing • Shelterbelts • Conservation tillage

24 Soil conservation As a result of the Dust Bowl, the U.S. Soil Conservation Act of 1935 and the Soil Conservation Service (SCS) were created. SCS: Local agents in conservation districts worked with farmers to disseminate scientific knowledge and help them conserve their soil.

25 Crop rotation Alternating the crop planted (e.g., between corn and soybeans) can restore nutrients to soil and fight pests and disease. Figure 8.16a

26 Contour farming Planting along contour lines of slopes helps reduce erosion on hillsides. Figure 8.16b

27 Intercropping Mixing crops such as in strip cropping can provide nutrients and reduce erosion. Figure 8.16c

28 (c) Alley cropping

29 Terracing Cutting stairsteps or terraces is the only way to farm extremely steep hillsides without causing massive erosion. It is labor-intensive to create, but has been a mainstay for centuries in the Himalayas and the Andes.

30 Shelterbelts Rows of fast-growing trees around crop plantings provide windbreaks, reducing erosion by wind. Figure 8.16e

31 Conservation tillage Conservation tillage is not a solution for all crops everywhere. It often requires more chemical herbicides (because weeds are not plowed under). It often requires more fertilizer (because other plants compete with crops for nutrients). No-till and reduced-tillage farming leaves old crop residue on the ground instead of plowing it into soil. This covers the soil, keeping it in place. Here, corn grows up out of a “cover crop.” But legume cover crops can keep weeds at bay while nourishing soil, and green manures can be used as organic fertilizers. Figure 8.16f

32 Trade-Offs Conservation Tillage
Reduces erosion Saves fuel Cuts costs Holds more soil water Reduces soil compaction Allows several crops per season Does not reduce crop yields Reduces CO2 release from soil Can increase herbicide use for some crops Leaves stalks that can harbor crop pests and fungal diseases and increase pesticide use Requires investment in expensive equipment Disadvantages Advantages Trade-Offs Conservation Tillage

33 Central Case: No-Till Agriculture in Brazil
Southern Brazil’s farmers were suffering falling yields, erosion, and pollution from agrichemicals. They turned to no-till farming, which bypasses plowing. Erosion was reduced, soils were enhanced, and yields rose greatly. No-till methods are spreading worldwide.

34 Irrigation The artificial provision of water to support agriculture
70% of all freshwater used by humans is used for irrigation. Irrigated land globally covers more area than all of Mexico and Central America combined. Irrigation has boosted productivity in many places … but too much can cause problems.

35 Waterlogging and salinization
Overirrigation can raise the water table high enough to suffocate plant roots with waterlogging. Salinization (buildup of salts in surface soil layers) is a more widespread problem. Salt in soils decreases the osmotic potential of the soil so that plants can't take up water from it. The salts can also be directly toxic, but plant troubles usually result primarily from inability to take up water from salty soils Evaporation in arid areas draws water up through the soil, bringing salts with it. Irrigation causes repeated evaporation, bringing more salts up.

36 Solutions Soil Salinization
Reduce irrigation Switch to salt- tolerant crops (such as barley, cotton, sugar beet) Prevention Flushing soil (expensive and wastes water) Not growing crops for 2-5 years Installing under- ground drainage systems (expensive) Cleanup Solutions Soil Salinization

37 Global fertilizer usages
Fertilizer use has risen dramatically in the past 50 years. Figure 8.19b

38 Inorganic Commercial Fertilizers
Trade-Offs Inorganic Commercial Fertilizers Advantages Disadvantages Do not add humus to soil Reduce organic matter in soil Reduce ability of soil to hold water Lower oxygen content of soil Require large amounts of energy to produce, transport, and apply Release the greenhouse gas nitrous oxide (N2O) Runoff can overfertilize nearby lakes and kill fish Easy to transport Easy to store Easy to apply Inexpensive to produce Help feed one of every three people in the world Without commercial inorganic fertilizers, world food output could drop by 40%

39 Overgrazing When livestock eat too much plant cover on rangelands, impeding plant regrowth. The contrast between ungrazed and overgrazed land on either side of a fenceline can be striking. Figure 8.22

40 Overgrazing Overgrazing can set in motion a series of positive feedback loops. Figure 8.21

41 Global food production
World agricultural production has risen faster than human population. Figure 9.1

42 Global food security However, the world still has 800 million hungry people, largely due to inadequate distribution. Considering soil degradation, can we count on food production continuing to rise? Global food security is a goal of scientists and policymakers worldwide.

43 Nutrition (causes numerous diseases, esp. in developing world)
Undernourishment = too few calories (especially developing countries) Overnutrition = too many calories (especially developed world) Malnutrition = lack of nutritional requirements (causes numerous diseases, esp. in developing world) Figure 9.2

44 Food Production, Nutrition and Environmental Effects
~ 1 in 6 people in developing nations are chronically undernourished or malnourished Common nutritional deficiency diseases: Marasmus and Kwashiorkor M = diet low in calories and protein K = severe protein deficiency

45 Feedback loop Poverty Malnutrition Decreased resistance to disease
High death rate for children energy ability to learn to work Shortened life expectancy Feedback loop Fig. 12.9, p. 269

46 Environmental effects of food production
Biodiversity Loss Loss and degradation of habitat from clearing grasslands and forests and draining wetland Fish kills from pesticide runoff Killing of wild predators to protect livestock Loss of genetic diversity from replacing thousands of wild crop strains with a few monoculture strains Soil Erosion Loss of fertility Salinization Waterlogging Desertification

47 Air Pollution Water Greenhouse gas emissions from fossil Fuel issue
Other air pollutants from fossil fuel use Pollution from pesticide sprays Water Water waste Aquifer depletion Increased runoff and flooding from land cleared to grow crops Sediment pollution from erosion Fish kills from pesticide runoff Surface and groundwater pollution from pesticides and fertilizers Overfertilization of lakes and slow-moving rivers from runoff of nitrates and phosphates from fertilizers, livestock wastes, and food processing wastes

48 Human Health Nitrates in drinking water
Pesticide residues in drinking water, food, and air Contamination of drinking and swimming water with disease organisms from livestock wastes Bacterial contamination of meat

49 Pesticide use Pesticide use is still rising sharply across the world, although growth has slowed in the U.S. 1 billion kg (2 billion lbs.) of pesticides are applied each year in the U.S. Figure 9.5

50 Biological control Synthetic chemicals can pollute and be health hazards. Biological control (biocontrol) avoids this. Biocontol entails battling pests and weeds with other organisms that are natural enemies of those pests and weeds. (“The enemy of my enemy is my friend.”)

51 Biological control Biocontrol has had success stories.
Bacillus thuringiensis (Bt) = soil bacterium that kills many insects. In many cases, seemingly safe and effective. Cactus moth, Cactoblastis cactorum (above), was used to wipe out invasive prickly pear cactus in Australia. Figure 9.7

52 But biocontrol is risky
Most biocontrol agents are introduced from elsewhere. Some may turn invasive and become pests themselves! Cactus moths brought to the Caribbean jumped to Florida, are eating native cacti, and spreading. Wasps and flies brought to Hawaii to control crop pests are parasitizing native caterpillars in wilderness areas.

53 Integrated pest management (IPM)
Combines biocontrol, chemical, and other methods May involve: • Biocontrol • Pesticides • Close population monitoring • Habitat modification • Crop rotation • Transgenic crops • Alternative tillage • Mechanical pest removal

54 Genetic modification of food
Manipulating and engineering genetic material in the lab may represent the best hope for increasing agricultural production further without destroying more natural lands. But many people remain uneasy about genetically engineering crop plants and other organisms.

55 Some GM foods Golden rice: Enriched with vitamin A. But too much hype?
FlavrSavr tomato: Better taste? But pulled from market. Ice-minus strawberries: Frost-resistant bacteria sprayed on. Images alarmed public. Bt crops: Widely used on U.S. crops. But ecological concerns? Figure 9.12

56 Prevalence of GM foods Figure 9.13

57 Scientific concerns about GM organisms
Are there health risks for people? Can transgenes escape into wild plants, pollute ecosystems, harm organisms? Can pests evolve resistance to GM crops just as they can to pesticides? Can transgenes jump from crops to weeds and make them into “superweeds”? Can transgenes get into traditional native crop races and ruin their integrity?

58 Socioeconomic and political concerns about GM products
Should scientists and corporations be “tinkering with” our food supply? Are biotech corporations testing their products adequately, and is outside oversight adequate? Should large multinational corporations exercise power over global agriculture and small farmers?

59 Europe vs. America Europe: has followed precautionary principle in approach to GM foods. Governments have listened to popular opposition among their citizens. U.S.: GM foods were introduced and accepted with relatively little public debate. Relations over agricultural trade have been uneasy, and it remains to be seen whether Europe will accept more GM foods from the U.S.

60 Genetically Modified Food and Crops
Projected Disadvantages Need less fertilizer Need less water More resistant to insects, plant disease, frost, and drought Faster growth Can grow in slightly salty soils Less spoilage Better flavor Less use of conventional pesticides Tolerate higher levels of pesticide use Higher yields Advantages Trade-Offs Genetically Modified Food and Crops Irreversible and unpredictable genetic and ecological effects Harmful toxins in food From possible plant cell Mutations New allergens in food Lower nutrition Increased evolution of Pesticide-resistant Insects and plant disease Creation of herbicide- Resistant weeds Harm beneficial insects Lower genetic diversity

61 Preserving crop diversity
Native cultivars of crops are important to preserve, in case we need their genes to overcome future pests or pathogens. Diversity of cultivars has been rapidly disappearing from all crops throughout the world.

62 Seed banks preserve seeds, crop varieties
Seed banks are living museums of crop diversity, saving collections of seeds and growing them into plants every few years to renew the collection. Careful hand pollination helps ensure plants of one type do not interbreed with plants of another. Figure 9.14

63 Animal agriculture: Livestock and poultry
Consumption of meat has risen faster than population over the past several decades. Figure 9.15

64 Feedlot agriculture Increased meat consumption has led to animals being raised in feedlots (factory farms), huge pens that deliver energy-rich food to animals housed at extremely high densities. Figure 9.16

65 Feed lots More production of livestock in smaller, condensed spaces; Produce more using less space and energy Increases need for antibiotics due to enclosed spaces; leads to issues of cruelty to animals Hormones given to produce larger animals for more meat= more $!

66 Feedlot agriculture: Environmental impacts
Immense amount of waste produced, polluting air and water nearby Intense usage of chemicals (antibiotics, steroids, hormones), some of which persist in environment However, if all these animals were grazing on rangeland, how much more natural land would be converted for agriculture?

67 Food choices = energy choices
Energy is lost at each trophic level. When we eat meat from a cow fed on grain, most of the grain’s energy has already been spent on the cow’s metabolism. Eating meat is therefore very energy inefficient. - Hence, the “Eating Green” Challenge! Feb. 28- March 7

68 Grain feed input for animal output
Some animal food products can be produced with less input of grain feed than others. Figure 9.17

69 Land and water input for animal output
Some animal food products can be produced with less input of land and water than others. Figure 9.18

70 Aquaculture The raising of aquatic organisms for food in controlled environments Provides 1/3 of world’s fish for consumption 220 species being farmed The fastest growing type of food production

71 Benefits of aquaculture
Provides reliable protein source for people, increases food security Can be small-scale, local, and sustainable Reduces fishing pressure on wild stocks, and eliminates bycatch Uses fewer fossil fuels than fishing Can be very energy efficient

72 Environmental impacts of aquaculture
Density of animals leads to disease, antibiotic use, risks to food security. It can generate large amounts of waste. Often animals are fed grain, which is not energy efficient. Sometimes animals are fed fish meal from wild-caught fish. Farmed animals may escape into the wild and interbreed with, compete with, or spread disease to wild animals.

73 Catching and Raising More Fish
Fisheries Fishing methods (See Fig p. 299) Sustainable yield Overfishing- decreased biodiversity; affects aquatic food chains; bycatch; loss of food Commercial extinction Aquaculture- collectively involves fish farming and ranching; salmon and shrimp

74 Environmental impacts of aquaculture
Transgenic salmon (top) can compete with or spread disease to wild salmon (bottom) when they escape from fish farms. Figure 9.20

75 3 methods used to catch fish:
aquaculture 3 methods used to catch fish: trawl bag drift net purse-seine

76 Trade-Offs Aquaculture
Highly efficient High yield in small volume of water Increased yields through cross- breeding and genetic engineering Can reduce over- harvesting of conventional fisheries Little use of fuel Profit not tied to price of oil High profits Advantages Large inputs of land, feed, And water needed Produces large and concentrated outputs of waste Destroys mangrove forests Increased grain production needed to feed some species Fish can be killed by pesticide runoff from nearby cropland Dense populations vulnerable to disease Tanks too contaminated to use after about 5 years Disadvantages Trade-Offs Aquaculture

77 More Sustainable Aquaculture
Reduce use of fishmeal as a feed to reduce depletion of other fish Improve pollution management of aquaculture wastes Reduce escape of aquaculture species into the wild Restrict location of fish farms to reduce loss of mangrove forests and other threatened areas Farm some aquaculture species (such as salmon and cobia) in deeply submerged cages to protect them from wave action and predators and allow dilution of wastes into the ocean Set up a system for certifying sustainable forms of aquaculture Solutions More Sustainable Aquaculture

78 Sustainable agriculture
Agriculture that can practiced the same way far into the future Does not deplete soils faster than they form Does not reduce healthy soil, clean water, and genetic diversity essential for long-term crop and livestock production Low-input agriculture = small amounts of pesticides, fertilizers, water, growth hormones, fossil fuel energy, etc. Organic agriculture = no synthetic chemicals used. Instead, biocontrol, composting, etc.

79 Organic farming Small percent of market, but is growing fast
1% of U.S. market, but growing 20%/yr 3–5% of European market, but growing 30%/yr Organic produce: Advantages for consumers: healthier; environmentally better Disadvantages for consumers: less uniform and appealing-looking; more expensive

80 Conclusions: Challenges
Chemical pesticides pollute, and kill pollinators, and pests evolve resistance. GM crops show promise for social and environmental benefits, but questions linger about their impacts. Much of the world’s crop diversity has vanished. Feedlot agriculture and aquaculture pose benefits and harm for the environment and human health.

81 Conclusions: Challenges
Organic farming remains a small portion of agriculture. Human population continues to grow, requiring more food production. Soil erosion is a problem worldwide. Salinization, waterlogging, and other soil degradation problems are leading to desertification. Grazing and logging, as well as cropland agriculture, contribute to soil degradation.

82 Conclusions: Solutions
Biocontrol and IPM offer alternatives to pesticides. Further research and experience with GM crops may eventually resolve questions about impacts, and allow us to maximize benefits while minimizing harm. More funding for seed banks can rebuild crop diversity. Ways are being developed to make feedlot agriculture and aquaculture safer and cleaner.

83 Conclusions: Solutions
Organic farming is popular and growing fast. Green revolution advances have kept up with food demand so far. Improved distribution and slowed population growth would help further. Farming strategies like no-till farming, contour farming, terracing, etc., help control erosion. Government laws, and government extension agents working with farmers, have helped improve farming practices and control soil degradation. Better grazing and logging practices exist that have far less impact on soils.

84 Sustainable Agriculture
High-yield polyculture Organic fertilizers Biological pest control Integrated pest management Irrigation efficiency Perennial crops Crop rotation Use of more water- efficient crops Soil conservation Subsidies for more sustainable farming and fishing Increase Soil erosion Soil salinization Aquifer depletion Overgrazing Overfishing Loss of biodiversity Loss of prime cropland Food waste Subsidies for unsustainable farming and fishing Population growth Poverty Decrease Solutions Sustainable Agriculture

85 Sustainable Agriculture
Waste les food Reduce or eliminate meat consumption Feed pets balanced grain foods instead of meat Use organic farming to grow some of your food Buy organic food Compost your food wastes What Can You Do? Sustainable Agriculture


87 QUESTION: Review Integrated pest management may involve all of the following EXCEPT… ? a. Close population monitoring b. Biocontrol c. Exclusive reliance on pesticides d. Habitat modification e. Transgenic crops Answer = c

88 QUESTION: Review What do seed banks do?
a. Lend money to farmers to buy seeds b. Pay farmers to store seeds c. Buy seeds from farmers d. Store seeds to maintain genetic diversity e. None of the above Answer = d

89 QUESTION: Review Which is NOT a benefit of aquaculture?
a. Provides a reliable protein source b. Reduces pressure on natural fisheries c. Produces no waste d. Uses fewer fossil fuels than commercial fishing e. All of the above are benefits Answer = c

90 QUESTION: Weighing the Issues
Can we call the green revolution a success? a. A huge success; it has saved millions from starvation because it increased food production to keep pace with population growth. b. Not a success; its environmental impacts have outweighed its claimed benefits. c. A success; its environmental impacts are balanced by the fact that it saved huge areas from deforestation. Answer = personal opinion

91 QUESTION: Interpreting Graphs and Data
With 500 kg of water, you could produce … ? a. 2 kg of protein from milk b. Protein from 50 chickens c. 750 kg of protein from beef d. 15 eggs Answer = a Figure 9.18b

92 QUESTION: Viewpoints Should we encourage the continued development of GM foods? a. Yes; they will bring many health, social, and environmental benefits. b. No, we should adopt the precautionary principle, and not introduce novel things until we know they are safe. c. Yes, but we should proceed cautiously, and consider each new crop separately. Answer = personal opinion

93 QUESTION: Review Which statement is NOT correct?
a. Soil consists of disintegrated rock, organic matter, nutrients, and microorganisms. b. Healthy soil is vital for agriculture. c. Soil is somewhat renewable. d. Soil is lifeless dirt. e. Much of the world’s soil has been degraded. Answer = d

94 QUESTION: Review The A horizon in a soil profile… ?
a. Is often called the “zone of accumulation.” b. Is often called “topsoil.” c. Contains mostly organic matter. d. Is the lowest horizon, deepest underground. Answer = b

95 QUESTION: Review Erosion occurs through… ? a. Deforestation.
b. Excessive plowing. c. Overgrazing rangelands. d. Two of the above. e. All of the above. Answer = e

96 QUESTION: Review Drip irrigation differs from conventional irrigation in that … ? a. It is much less efficient. b. It can cause salinization. c. Water is precisely targeted to plants. d. About 40% is wasted. Answer = c

97 QUESTION: Weighing the Issues
You are farming an extremely steep slope that is sunny and very windy. What strategies would you consider using? a. Crop rotation b. Contour farming c. Intercropping d. Terracing e. Shelterbelts f. No-till farming Answer = personal opinion, but d & e would be first priority

98 QUESTION: Interpreting Graphs and Data
Grain produced per person has… ? a. Risen steadily b. Fallen sharply c. Increased since 1983 d. Decreased since 1983 Answer = d Figure 8.3

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