Chapter 11: Agriculture, Aquaculture and the Environment

1. Chapter 11:Agriculture, Aquaculture and the Environment

2. Overview • An Ecological Perspective on Agriculture • Can We Feed The World? • What We Grow on the Land • Soils • Controlling Pests • The Future of Agriculture • Genetically Modified Food: Biotechnology, Farming, and Environment • Aquaculture

4. Agroecosystem Ecological succession stopped to keep the agroecosystem in an early-successional state Focus on Monoculture Monoculture - large areas planted with a single species Counteracted by crop rotation Crops planted in neat rows and fields Makes crops vulnerable to pests

5. Farming greatly simplifies biological diversity and food chains Plowing is unlike any natural soil disturbance Nothing in nature repeatedly and regularly turns over the soil to a specific depth Genetic modification of crops Agroecosystem

6. Can We Feed the World? To answer this we must understand how crops grow and how productive they can be Most viable of human activities but is it sustainable? Regions farmed for thousands of years Farming changed local ecosystems

8. Can We Feed the World? History of agriculture is a series of human attempts to overcome environmental limitations and problems. Each solution creates new problems Should expect some side effects Multiple pressures on agricultural land

10. Can We Feed the World? As population grows, the production of agriculture must grow Food supply is already inadequate for some peoples Increasingly marginal land will need to be put into production Food supply also greatly influenced by social disruptions and social attitudes

11. How We Starve People “starve” in two ways Undernourishment Lack of sufficient calories in available food Manifests as famine Malnourishment Lack of specific chemical components of food, such as protein, vitamins, or other essential chemical elements

12. How We Starve Undernourishment Marasmus – progressive emaciation caused by lack of protein and calories Kwashiorkor – a lack of sufficient protein in the diet Chronic hunger – enough food to stay alive but can not live satisfactory or productive lives

13. How We Starve World food production must provide adequate nutritional quality and quantity. Food emergencies affected 34 countries worldwide at the end of 20th century Africa has the most acute food shortages Food distribution major problem World food aid does not meet all the caloric need of people Best solution is to increase local production

16. What We Grow on the Land Crops Of Earth’s ½ million plant species, only about 3,000 are agricultural crops 150 species cultivated on large scale Most of world’s food provided by 14 crop species 6 provide 80% of the total calories

18. Livestock Forage- crops grown for domestic animals In US 14 million areas of alfalfa Domestic animals include 14 billion chickens 1.3 million cattle ~1 billion each sheep, ducks and pigs 700 million goats 160 million water buffalo 18 million camels

19. Livestock Rangeland Provides food for grazing and browsing animals w/o plowing and planting Pasture Plowed, planted and harvested to provide forage Large world market in small grain crops See next slide

21. Livestock- effect on environment • About half the earth’s land area is used as rangeland • Most is easily damaged by grazing (drought) • Much of the rangeland is overgrazed • Grazing cattle trample stream banks and release waste into streams

22. Soils • Soils are not just “dirt” • Key to life on land • Earth modified over time by physical, chemical and biological processes into a series of layers called horizons • O horizon - organic layer on top of soil • A (& E in some soils) horizon- upper horizon • B horizon - zone of accumulation • C horizon - most similar to parent material

24. Soils • Soil fertility • Capacity of a soil to supply nutrients necessary for plant growth • Geologically younger soils are typically more fertile • Soil Drainage • Soils with high clay content hold water well • Soil with high sand content drain very well

25. Restoring Our Soils • Soil erosion has decreased 40% in US • Due to better farming practices • Use of chemical (artificial) fertilizers increased soil fertility in 20th century • Use of phosphorus (mined and in guano) in fertilizers increased soil fertility

26. Limiting Factors Crops require 20 chemical elements at the right amount at the right time of year Macronutrients micronutrients High-quality agricultural soil has All the chemical elements required for plants A physical structure that lets air and water move freely Retains water well Mixture of soil particle size

27. Limiting Factors Liebig’s Law Single factor determines the growth and therefore the presence of a species Growth of a plant is affected by one limiting factor at a time

28. Limiting Factors Two elements may have a synergistic effect A change in the availability of one resource affects the response of an organism to some other resource. Chemical elements may become toxic when levels are to high

29. Controlling Pests • Pests are undesirable • Competitors, parasites, and predators • Agricultural pests include: • Insects • Nematodes • Bacterial and viral diseases • Weeds • Vertebrates • Loss can be large • Estimated at 1/3 of potential harvest and 1/10 of the harvested crop

30. Controlling Pests • Farms are maintained in early stage of ecological succession and enriched by fertilizers and water • Great area for crops • Great area for early-successional plants (weeds) • Weeds compete for all resources • Light, water,nutrients, and space to grow

31. Pesticides- History • Stage 1 Broad Spectrum Inorganic Toxins • Search for chemicals that would reduce abundance of pests • Goal was narrow-spectrum (species-specific), but most were broad-spectrum • Ex: Arsenic, toxic to all life • Killed pest and beneficial organisms

32. Pesticides- History • Stage 2: Petroleum based sprays and natural plant chemicals • 1930’s • Ex: nicotine

33. Pesticides- History • Stage 3: Artificial Organic Compounds • DDT, broad-spectrum • Aldrin and dieldrin used to control termites • Problems • Toxic to humans, has been found in breast milk • Secondary Outbreaks • Pests develop resistance

35. Pesticides- History • Stage 4: Return to biological and ecological knowledge • IPM - Integrated Pest Management • Goal is to reduce use of artificial pesticides • Biological control- the use of biological predators and parasites to control pests • Bacillusthuringiensis(BT) - Proved safe and effective

36. Integrated Pest Management IPM uses a combination of methods • Biological control • Chemical pesticides • Methods of planting crops (mixed fields) • Goal can be control not elimination of pest • Economically makes sense • Does less damage to ecosystem, soil, water and air

37. Biological Control • Other biological control agents • Small wasps that parasitize caterpillars • Both effective and narrow spectrum • Ladybugs • Sex pheromones (chemicals released to attract opposite sex) used as bait in traps

39. The Future of Agriculture Three major technological approaches to agriculture Modern mechanized agriculture Resource-based agriculture Organic food production Bioengineering

40. How can crop production keep up with population growth? • Increased production per acre • Technology driven • New Crops and Hybrids • New or yet unused plants could do well in poorer agricultural soil • Green Revolution

41. The Green Revolution Name attached to the post WWII programs that have led to the development of new strain of crops w/ higher yield better resistance to disease or better ability to grow under poor conditions

42. How can crop production keep up with population growth? Better irrigation techniques Could improve crop yield and reduce overall water use Drip irrigation Hydroponics Eating Lower on Food Chain Same area of land could produce 10–100 times more vegetation than meat per year

43. How can crop production keep up with population growth? Organic faming Three qualities More like nature ecosystem than monoculture Minimizes negative environmental impacts The food that results does not contain artificial compounds One of the fastest growing sectors in US agriculture

44. Genetically Modified Food Scientist have been able to transfer specific genetic characteristics from one individual to another, from one population to another, and from one species to another. Genetic engineering in agriculture involves several practices Faster and more efficient ways to develop hybrids Introduction of the terminator gene Transfer of genetic properties from widely divergent kinds of life

45. Genetically Modified Food Considerable interest in developing crops With entirely new characteristics E.g. nitrogen fixation With tolerance of drought, cold, heat and toxic chemical elements.

46. Genetically Modified Crops • Three methods • 1. Faster and more efficient development of new hybrids • 2. Introduction of the “terminator gene” • 3. Transfer of genetic properties from widely divergent kinds of life

47. New Hybrids • From an environmental perspective, genetic engineering to develop hybrids w/in a species is likely to be a benign as the development of agricultural hybrids has been w/ conventional methods. • Concern that genetic modification may produce • “superhybrids” • Could become pest or transfer genes to closely related weeds

48. The Terminator Gene • Makes seeds from a crop sterile • Done for environmental and economic reasons • Prevents a gmo from spreading • Protects the market for the corporation that developed it • Critics note • Farmer’s in poor nations must be able to grow next years crops from their own seeds

49. Transfer of Genes • Genes transfer from one major life form to another • Most likely to have negative and undesirable impacts • E.g., Bacillusthuringiensis • Produce toxin that kills caterpillars • Gene identified and transferred to corn • Engineered corn now produces its own pesticide

50. BT corn contains its own pesticide in every cell of the plant. Bacillus thuringiensis bacteria (a natural pecticide). The gene that caused the pecticide (BT) was placed in corn through genetic engineering. Pollen from the BT corn is also toxic and when it lands on milkweed, monarch butterflies that eat the milkweed may die.