Ch 11: Feeding the World

Transcription

1 Ch 11: Feeding the World Special Topics These lectures contain copyrighted images that are provided in the teacher materials for Friedland/Relyea Environmental Science for AP Textbook. By using these lectures, you guarantee that you have legal access to these images or that you have replaced the copyrighted images with images that you have the rights to use.

2 The Life-cycle of Food

3 The Green Revolution How we got here 1. Plant monocultures of selectively bred or genetically engineered highyield varieties of rice, wheat or corn that are disease resistant. 2. Add large inputs of water, fertilizer and pesticides to ensure high yields 3. Get more crops from the same land by multi-cropping Pros Increased food production allowing us to feed a rapidly growing world, more food on less land, reduced undernutrition and malnutrition significantly Cons Requires huge inputs of oil, water and fertilizer resulting in serious environmental impacts, may not be sustainable, may permanently damage soil quality, and many more

4 Impacts of Industrial Agriculture

5 Vitamin Deficiencies (malnutrition) Deficiency Symptoms Solutions Iron Anemia (fatigue, infections, increased risk of death during childbirth) Iron pills Eat more meat, lentils or enriched grains (fortified) Vitamin A Iodine (Common in mountainous regions with poor soil) Childhood blindness, increased risk of infection Goiter (swelling of the thyroid gland), stunted growth, impaired mental capabilities Golden rice (GMO with beta carotine), more dairy, more leafy greens, supplements Eat seafood Iodized salt

6 Irrigation Methods Process dig a trench and fill with water Pros - Cheap and easy, gravity driven Cons water is lost to evaporation and runoff Efficiency 65% Process flood the field and let water soak in Pros cheap and easy, gravity driven Cons may disrupt plant growth, water is lost to evaporation and runoff Efficiency 70-80%

7 Irrigation Methods Process water is pumped to nozzles that spray water across the field Pros more efficient choice Cons more expensive, requires energy, water is lost to evaporation and runoff Efficiency 75-95% Process hoses with small pores are laid near roots or buried below soil Pros reduced weed growth (surface soil is dry) Cons work best in perennial fields since hoses have to moved for plowing and planting (which = time and money) Efficiency more than 95%

8 Problems with Irrigation Soil Salinization Repeated irrigation evaporation Evaporation leaves small salt deposits behind. Over time the salt deposits build up and can be toxic to plants Clean-up: flood field and start over, leach salts out Prevention: install better drainage systems, use more efficient irrigation systems Water Logging Repeated irrigation rising water table Rising water tables flood roots, deprive bacteria of oxygen Clean up: wait for fields to drain Prevention: install better drainage systems, use more efficient irrigation systems

9 Other Soil Problems Compaction soil is crushed by machinery, closing pore spaces Pore spaces provide oxygen for soil organisms, space for roots and water infiltration Solutions: aerate soil, plant cover crops in the off season, no till agriculture Erosion soil is blown away by wind or washed away by water due to a lack of root structures Top soil and nutrients are lost, reducing plant growth, runoff pollutes waterways Solutions: plant cover crops in off season, no till agriculture, leave crop residue on fields

10 Desertification Repeated insults to soil including compaction, salinization, waterlogging and erosion can slowly turn once productive areas into deserts Most common in the areas directly adjacent to a desert, but increasingly happening in areas that have been clear-cut for logging purposes Generally an irreversible process Land can sometimes be used for nomadic grazing Consequences: Loss of food production, dust storms, environmental refugees, famines, droughts

11 Organic Fertilizer Animal Manure waste products from animals Pros: free if animals on same farm, provide organic matter and trace nutrients, improves soil structure, support soil organisms Cons: expensive to transport, possible spread of diseases, slow to release nitrogen (must be applied before growing season) Green manure freshly cut green vegetation plowed into soil Pros: increase organic matter and humus, if grown on site they conserve soil, fix nitrogen, and encourage beneficial insect growth,

12 Organic Fertilizer (cont) Compost broken down food, paper and leaves Pros: free if produced on site, saves landfill space, provides organic material and improves soil structure, support microorganisms Cons: slow to release nutrients (many are trapped in organic form), potentially high salt content, weed seeds from fruits and veggies, excess ammonia can burn roots

13 Inorganic Fertilizer Commercial inorganic fertilizers fertilizers often made from fossil fuels that provide N, P, K Pros: greatly increase productivity, cheap, readily available, immediately increase soil fertility Cons: Lack trace nutrients Do not provide organic material Do not improve soil structure or support soil organisms May runoff into water bodies causing eutrophication/dead zones/health impacts Usually made from non-renewable resources Release nitrous oxide (GHG) and NOx (air pollutant)

14 Producing Meat Rangeland and Pastures animals roam around mostly untended land, grazing Pros: less environmental impact (usually) Cons: uses lots of land = less meat, overgrazing can occur, threats from predators, expensive, can cause overgrazing and erosion

15 Producing meat (cont) Concentrated Animal Feedlot Organizations (CAFO) animals are concentrated in an enclosed area and fed grain or fish meal Pros: less land more meat, higher profits, less habitat loss, overgrazing and erosion Cons: large inputs of grain, water and fossil fuels, concentrated animal waste, overuse of antibiotics and hormones (steroids)

16 Efficiency: Feedlot Concerns 70% of corn grown in US and 80% of worlds soybeans go to feeding livestock One pound of beef requires gal of water, 16 lbs of grain and 0.75 gal of oil It is much more efficient to feed humans directly with the grains than to filter through animals (10% rule) Antibiotic and growth hormone use Make cows live longer and grow larger, but may lead to antibiotic resistance. Hormones may pass into humans (rbst suspected endocrine disruptor). Methane cows burp/fart 16% of the methane released (contributes to global warming) Waste only 50% of animal waste from feedlots is returned to the soil as fertilizer, runoff leads to eutrophication and drinking water contamination

17 Fishing Methods Major problems with fishing include: Overfishing due to overly effective fishing techniques Subsidies that make fish too cheap Bycatch

18 Aquaculture Raising marine and freshwater fish in ponds and underwater cages like a feedlot for fish Pros: Efficient: less water/space more fish, takes pressure off wild species, low fuel usage, high profits Cons: Need lots of land, feed and water, lots of waste, may destroy estuaries and wetlands, may use grain supply, dense populations increase disease increased use of antibiotics, bioaccumulation of toxins (PCBs, mercury, dioxins, etc) if benthic soil is contaminated Possible solution aquaculture in the open ocean or way inland

19 Food prices, oil and subsidies Food prices are strongly correlated with oil prices because modern agriculture is so mechanized and thus oil dependent. As oil prices increase, so will food prices. Agriculture is a risky business because weather, crop prices and pests are unpredictable and can wipe out entire seasons of crops. Governments try to control prices or subsidize farmers to keep food prices low Governments may also pay farmers not to plant in order to keep prices up What should we do: Subsidize sustainable farming operations and efficient irrigation systems, fund research into best practices, establish training programs to promote efficient irrigation, alternatives to pesticides and soil management, support locally grown food.

20 Picture Quizzes!

21 Which type of agriculture is each picture showing? Choices: Industrial agriculture No Till agriculture Nomadic grazing Slash and burn Traditional agriculture

22 Which soil conservation technique is shown in each picture? Choices: Agroforestry Contour Planting No-till agriculture Strip cropping Terracing

23 Which growing methods are pictured below? Choices: Agroforestry Crop Rotation Intercropping Monoculture Polyculture