Chapter 7 Food & Agriculture Environmental Science Auburn ENVI-1020 Dr. Holm
Chapter 7 Food & Agriculture Environmental Science Auburn ENVI-1020 Dr. Holm ENVI 1020 - 001
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This 5 page Class Notes was uploaded by Cory Garfunkel on Monday April 18, 2016. The Class Notes belongs to ENVI 1020 - 001 at Auburn University taught by Robert F. Holm in Spring 2016. Since its upload, it has received 52 views. For similar materials see Fundamentals of Environmental Science in Science at Auburn University.
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Date Created: 04/18/16
Chapter 7 Food & Agriculture Globally, we need to be concerned about food quantity and quality to feed increasing numbers of hungry people in the world Chronic Hunger & Food Security—within families that don’t get enough to eat, women & children almost always have the poorest diets World Food Supplies: 1950-2000 o Richer countries: most common dietary problem is over-nutrition (obesity) US leads developed world with 61% of adults at least somewhat overweight o Sub-Saharan Africa: food production has not kept pace with rapid pop. growth o Asia: most rapid increase in crop production alongside rapid pop. growth World Food Problems o Pop. growth is surpassing food production in many areas of the world o Famine—large scale food shortages, massive starvation, social disruption, & economic chaos Causes: Environmental conditions, i.e. drought, insects, natural disasters National politics—corruption, oppression Armed Conflict Economics—price gouging, poverty, landlessness o Protein Deficiency Diseases Kwashiorkor or “Displaced Child”—mainly children with lack of high quality protein Marasmus “To Waste Away”—Caused by diet low in both protein & calories Major Food Sources o Crops Wheat, rice, & maize are responsible for the majority of the world's nutrients Potatoes, barley, oats & rye are staples in cool, moist climates Cassava, sweet potatoes, other roots & tubers are staples in warm, wet climates Sorghum & millet are drought resistant staples in dry regions of Africa Fruits, vegetables, & vegetable oils contain high levels of vitamins, minerals, dietary fiber & complex carbohydrates o Meat, Milk, & Seafood Milk & meat are highly prized, but their distribution is inequitable Developed countries make up 20% of world pop., but consume 80% of meat & milk production, whereas less developed countries produce 60% of world's milk and meat ~90% of grain grown in N. Amer. feeds cattle, hogs, poultry, & other animals Seafood—important protein source in many countries threatened by over- harvesting & habitat destruction o 51% of seafood catch comes from oceans; 99% of that comes from coastal areaspotentially serious coastal devastation Food Production o Of the 50,000 species of edible plants, only ~30 crops feed the world & 14 produce 90% of our food o 4 crops—wheat, rice, corn & potato make up more of world’s total food prod. than all others combined o 8 species of domesticated livestock provide the majority of meat, eggs, milk, & cheese o ~2/3 of world’s population survives on a primarily vegetarian diet (Why?) Recall Energy Chain (Primary vs. Secondary vs. Tertiary consumers) o Types of Agriculture/Food Production Industrialized (high-input) agriculture (Pretty much all of US now) Large quantities of single type of crop/livestock within country & for export Plantation agriculture Traditional subsistence agriculture Produces enough crops or livestock for (subsistence) survival Traditional intensive agriculture Produce enough for a surplus & to feed a family Nomadic Herding Shifting Cultivation—Use land, let revert to natural vegetation, move on o Green Revolution 1 in developed countries (1950-70), then in Developing Countries (Post-1967) Develop plant monocultures High yields with additional fertilizers, pesticides, & water Over time, yield normalizes and we lose the advantagePesticide treadmill Multiple cropping (Crop rotation) Environmental impacts (hopefully good) Energy use (hopefully lower) Social Consequences? Who does it benefit? o Increasing Food Production Increase amount of agricultural land—Concerns? Currently, 51% of land isn’t usable for grazing or farming, and almost half of usable land is being usedcan’t really use much more Options o Clear tropical forests Nutrient-poor soils don’t permit sustainable agriculture Removal of valuable carbon sink & loss of biodiversity o Irrigate arid lands Expensive damsdepletion of groundwater supplies Profitable, sustainable expansion of cropland unlikely over next few decades Switch to non-traditional crops—risks? Cultivate less widely known plants and perennial plants o Reduce use of water, fertilizer, energy, & erosion Eating Insects Soil enrichment Genetic engineering (Third Green Revolution) Genetically modified foods (GMF) o Increase proportion of photosynthesis going to food New Strains of traditional crops resistant to disease, insects, & drought Fisheries 11 of world’s 15 major oceanic fishing areas fished at or over capacity for commercially valuable species & are in state of decline Why? o Growing demand for seafood o Efficient, large-scale industrial fishing fleets o Degradation & destruction of coastal wetlands o Pollution of coastal waters Aquaculture—The Blue Revolution o Fish Farming & Ranching High yields in small volume of water Increase yields by crossbreeding & genetic engineering o Limitations Conversion of coastal wetlands to fish farms Genetic pollution of natural fish populations by escapees Contamination of nearby waters with waste & chemicals Sustainable Agriculture Efficient irrigation Increased use of organic fertilizers Biological pest control & integrated pest management Soil conservation Organic farming o Major Environmental Effects of Food Production Biodiversity Loss Loss/degradation of habitat via clearing grasslands & forests & draining wetlands 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 All of US is either of some or serious concern regarding soil erosion Water Water waste & Aquifer depletion Increased runoff and flooding from land cleared to grow crops Sediment pollution from runoff Surface & groundwater pollution from pesticides & fertilizers Over-fertilization of lakes & slow-moving rivers from runoff of nitrates & phosphates from fertilizers, livestock wastes, & food processing wastes Types: Sheet, rill, gully, streambank Air Pollution Greenhouse gas emissions & other pollutants from fossil fuel use, inorganic fertilizers, and livestock Pollution from Pesticide Sprays Human Health Nitrates & pesticide residue in drinking water, food, & air Contamination of water with diseases from livestock waste Bacterial contamination of meat Soil—complex mix of weathered minerals, partially decomposed organic matter, & living organisms o We depend on soil for life, yet tend to take this living resource for granted o U.S. has > 20,000 different soil types that vary due to influences of parent material, time, topography, climate, & organisms o About 30-50% of the world's croplands are losing topsoil faster than it can be replaced o Renewable resource, but building good soil is slow process (500 yrs or more per inch topsoil) o Parts (Top-down) O-Horizon—Surface litter: freshly fallen leaves & organic debris & partially decomposed organic matter (PDOM) A-Horizon—Topsoil: PDOM (humus), living organisms, & some inorganic minerals E-Horizon—Zone of Leaching: dissolved or suspended materials move downward B-Horizon—Subsoil: accumulation of Fe, Al, & humus compounds, & clay leached down from A and E horizons C-Horizon—Parent Material: Partially broken-down inorganic minerals R-Horizon—Bedrock: Impenetrable layer Causes of Erosion o Intensive farming practices Row crops leave soil exposed, weed free-fields, removal of windbreaks, no crop- rotation or resting periods, continued monocultures o Construction sites Solutions: Soil Conservation o Conventional tillage, conservation tillage, cropping methods, windbreaks, land classification More Environmental Impacts o > 50% of world’s cropland is used to feed livestock o Over-grazing is the major cause of desertification of arid & semi-arid lands o Methane emissions of cattle o Cattle crowded into feedlots require large doses of antibiotics o Biological pests reduce crop yields & spoil as much as 50% of crops harvested annually Crops grown without synthetic fertilizers or pesticides tend to have lower yield, but have lower operating costs & less ecological damage Pesticides—Use 2.5 million tons/yr, ~ 1 lb./person on Earth o Chemicals that kill undesirable organisms o Insecticides, herbicides, fungicides, antibiotics, rodenticides, desiccants, plant regulators o First generation (1500’s-1940’s) Primarily natural substances—sulfur, lead, arsenic, mercury Plant extracts: nicotine, pyrethrum which are degradable o Second generation (1940’s-Present) Primarily synthetic organic compounds Broad- and narrow-spectrum agents Target and non-target species o Used for human well-being, regular component of ag. systems Quantity & quality of food supply would go down without them (price would ↑ too) In US, >600 Million kg/yr at a cost of $5,000,000 72% used in ag, 7% in home lawn/garden Insecticides—36% of use in ag, 50% in home lawn/garden Newer ones are becoming safer & being used at lower rates (still a problem) o Problems Lots of species now resistant though Can kill non-target & natural control species Can cause increase in other pest species Pesticide Treadmill—add, kill, genetic resistance gets passed on, add more, build resistance, etc. Don’t stay put, can harm wildlife, & have a wide range of human health threats o Ideal Pesticide Kill only target pests & harm nothing else Break down quickly Not cause genetic resistance More cost-effective than doing nothing o Other Ways to Control Pests Economic Threshold Adjusting cultivation practices Use genetically resistant plants Biological pest control Biopesticides Insect birth control Hormones & Pheromones Ionizing radiation
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