Chapter 15: Food & Agriculture 15-1 Feeding The World Famine: widespread starvation caused by a shortage of food Malnutrition: when people don’t consume enough Calories or do not eat a sufficient variety of foods to fulfill the body’s needs –Calorie: amount of energy available in foods Diet: type and amount of food that a person eats –The foods produced in the greatest amounts worldwide are grains (the seeds of grass plants) Yield: the amount of food that can be produced in a given area –Researchers want organisms that can survive various climates & require little fertilizer, pesticides, and water.

Food Efficiency measure of the quantity of food produced on a given area of land with limited inputs of energy & resources Ideal food crop = produces a large amount of food with little negative impact on the environment On average, more energy, water, and land are used to produce a Calorie of food from animals than to produce a Calorie of food from plants –Remember the 10% rule and the fact that carnivores eat higher up the food chain. –This is why diets around the world are largely plant-based. BUT… meat from animals generally provides more nutrients per gram than most food from plants.

World Food Problems More food is needed each year to feed the world’s growing population. Distribution problems and drought can lead to food shortages. 1. Unequal Distribution – If all the food in the world today were divided equally among the human population, no one would have quite enough food for good health. But food is not divided equally. Causes: poverty, wars and political strife that disrupt transportation systems, etc. 2. Droughts: a prolonged period during which rainfall is below average –If food is grown locally (not imported) then a drought can be even more severe by resulting in no seeds to plant crops for the following years.

The Green Revolution introduced new crop varieties with increased yields through the application of modern agricultural techniques. Negative Impacts: large amounts of water, fertilizer and pesticides were required for many of these new crops. –Machinery, irrigation, and chemicals required can degrade the soil if overused. –Overuse of fertilizers and pesticides has led to decreased yields and failure of some of these crops. –Subsistence Farmers: grow only enough food for local use Could not afford the equipment, water, and chemicals to grow the new crop varieties.

15-2 Crops and Soil Arable Land: can be used to grow crops. Limited Amount/person decreases as pop. grows Agriculture: Basic Processes of Farming: plowing, fertilization, irrigation, and pest control. Modern Agricultural Methods: have replaced traditional methods in much of the world (machinery, synthetic chemical fertilizers replaced manure, etc.) Fertile soil: can support the growth of healthy plants –Topsoil: surface layer of soil, usually richer in organic matter –Fertile Topsoil: living organisms + rock particles + water + air + organic matter (dead/decomposing organisms)

How Soil Forms: rock broken down into smaller pieces by 1. Wind 2. Water 3. Chemical Weathering: when minerals in rock react chemically with substances (like water) to form new materials 4. Frost Action: freezing moisture can cause rocks to crack Can take hundreds or even thousands of yrs. to form a few cm of soil Rock particles provide mineral nutrients Bacteria and fungi decompose dead matter – adding nutrients Earthworms, insects, other small animals – break up soil allowing are and water in

Soil Layers

Erosion: wearing away rock or soil by wind and water About ½ the original topsoil in the U.S. has been lost to erosion in the past 200 yrs. Most farming methods increase the rate of soil erosion Land Degradation: when human activity or natural processes damage the land so that it can no longer support the local ecosystem. Desertification: in dry climates land becomes more desert-like because of human activity or climatic changes Solutions: –Move grazing animals frequently –Allow land to lie fallow (remain unplanted for several years)

Soil Conservation important for protecting and managing topsoil and reducing erosion. Contour plowing: plowing across the slope of a hill instead of up and down the slope Leaving strips of vegetation across a hillside (to catch water and soil) instead of plowing the entire slope No-till farming: harvesting crops without turning over the soil (plowing soil to turn it over and bury the remains of harvested plants) –Seeds of the next crop are planted –Remains of the previous crop hold the soil in place while new crop develops –Advantage: significantly decreases soil erosion –Disadvantages: not suitable for some crops, lower crop yields over time

Contour Plowing

Terracing

No-Till Farming

Enriching the Soil Organic Matter: leaves, manure Inorganic Fertilizers: contain nitrogen, phosphorous, potassium – more than doubled world food production – erosion may pollute waterways Compost: partly decomposed organic material (lawn clippings, kitchen scraps) –Also reduces landfill waste Modern Method: compost + inorganic fertilizer Salinization: accumulation of salts in soil, when water evaporates leaving salts behind – can harm plants

Pest Control Pest: any organism that occurs where it is not wanted or that occurs in large enough numbers to cause economic damage Cause considerable crop damage (destroy about 33% of world’s potential food harvest) Pesticides: chemical used to kill insects, weeds, other crop pests –Pesticide Resistance: pest populations evolve the ability to survive exposure to a particular pesticides –Human Health Concerns: designed to kill organisms Correlated to increased cancer risk and nervous system disorders Protect yourself from contact –Pollution and Persistence Persistent: does not break down easily or quickly in the environment Accumulate in water and soil (can even be found in women’s breast milk)

Biological Pest Control: use of living organisms to control pests 1. Introduction of predators 2. Pathogens: organisms that cause disease 3. Plant defenses: breeding plant varieties that have defenses against pests (chemical compounds that repel pests, tougher skin, etc.) 4. Chemicals from Plants –ex. chemicals found in chrysanthemum plants now sold as pesticides –Less harmful to humans and pets –Biodegradable (break down by bacteria and other decomposers) 5. Disrupting Insect Breeding 6. Growth Regulators: chemicals that interfere with some stage of a pest’s life cycle –ex. flea pills (for dogs) prevent flea eggs from developing 7. Pheromones: chemicals produced by one organism that affect the behavior of another organism –ex. treat crops with moth pheromones that attract male moths, confuse them and interfere with mating

Wasp injecting eggs into an aphid.

Integrated Pest Management –can minimize the use of chemical pesticides –Goal: reduce pest damage to a level that causes minimal economic damage (not to eliminate pest populations)

IPM Preferred Methods 1. biological methods: predators, pathogens, parasites 2. cultivation controls (ex. vacuuming insects off plants) 3. Small amounts of insecticides (last resort, changed over time to reduce ability of pests to evolve resistance)

Genetic engineering: transferring genes from one organism to another –ex. transferring genes for resistance to pests –Plants that result from genetic engineering are called genetically modified (GM) plants. –GMO’s = genetically modified organisms –We eat many GMO’s every day –Many have not been fully tested for environmental impacts –Concerns about possible further exchange of genes in the wild

Sustainable Agriculture: a.k.a. low-input farming - farming that conserves natural resources and helps keep the land productive indefinitely –Involves planting productive, pest-resistant crop varieties that require little energy, pesticides, fertilizer, and water “Better Farming, Naturally” Proven ways to improve food production: 1. Increase yields with selective breeding techniques 2. Reduce chemical use by rotating crops 3. Increase erosion resistance and water-holding capacity of soil with reduced-till practices and cover crops

15-3 Animals in Agriculture Domesticated Animals: bred and managed for human use (chicken, sheep, cattle, honey bees, silk-worms, fish, shellfish, goats, pigs, etc.) Overharvesting: catching or removing from a population more organisms than the population can replace –Has reduced the populations of many aquatic organisms worldwide –Possible Solution = aquaculture: raising of aquatic animals (although it too has some problems…we’ll see in a later video)

Livestock: domesticated animals that are raised to be used on a farm or ranch or to be sold for profit Important for the production of food and other products (wool, leather, manure) Worldwide meat production per person has increased greatly over the past several decades. Ruminants: cud-chewing mammals that have 3 or 4 chambered stomachs –ex. cattle, sheep, goats –Cud: food these animals regurgitate from the 1st chamber of their stomachs and chew again –Have microorganisms in their intestines to digest plant materials humans can’t (converts plant material into food we can digest) Poultry: domesticated birds raised for meat and eggs (good sources of amino acids) –Ex. chickens, turkey Many livestock farms are huge, industrial-scale operations. (We’ll look at the effects in later video clips).