5.1-5.6

• Tragedy of the Commons

  • Originally coined by Economist William Foster Lloyd who used overgrazing as an example
  • Ecologist Garret Hardin wrote an essay titled Tragedy of the Commons
• Tragedy of the Commons

  • Individuals will use shared/public resources in their self interest, thus degrading them
  • Must be a public resource (not privately own) because the private owners would be affected
  • Must be degraded, overused, depleted, used-up in some way
• Name 3 examples of Tragedy of the Commons

  Overgrazing, overfishing, overuse of groundwater
• Why does the Tragedy of the Commons Happen

  • When no one owns the resource (land, air, water) no one directly suffers the negative consequences of depleting, degrading, or overusing it
  • People assume others will overuse the resource if they don't
  • There's no penalty for overusing, degrading, polluting many public resources
• The issue with Tragedy of the Commons

  • Overfishing can lead to fishery collapse (population crash), loss income, and starvation
  • Air pollution from coal power plants can lead to bronchitis, asthma, increased healthcare costs
  • Pesticide runoff from farms contaminates drinking water (Eutrophication)
• Externalities

  • Negative costs associated with human actions that arent accounted for in the price (unintended side-effects)
  • user doesn't experience it, but someone does
• Tragedy of the Commons: Solution

  • Private Land Ownership (Individual or Gov)
  • Someone will care for it
• Tragedy of the Commons: Solution

  • Fees or taxes for use; people will consider using less to not spend money
  • Permit system for grazing or logging
• Tragedy of the Commons: Solution

  • Taxes, fines, criminal charges for pollution or shared air/soil/water resources
  • Clean Air act, Clean Water act, Safe Drinking Water act
• Solution for Overgrazing

  • BLM (Bureau of Land Management)
  • BLM manages rangelands in the western US by collecting grazing fees from ranchers, evaluating land, and repairing the effects of overgrazing
• Clearcutting: Direct, Short-Term Effects

  Soil Erosion

  • Caused by loss of stabilizing root structure
  • Topsoil is more easily blown by wind
  • Removes soil organic matter and nutrients from forest
  • Deposits sediments in local streams
• Deposition of Sediments in Local Streams

  • Warms water and increase turbidity (suspended soils in a body of water)
  • Increased turbidity = oxygen isn't accessible for fish and plants can't get sunlight
• Clearcutting: Direct, Short-term Effects

  • Loss of tree shade increases soil temperature
  • Soil has lower albedo than leaves of trees
  • Loss of tree shade along rivers and streams warms them
  • Erosion of sediments into rivers also warms them (direct sunlight could kill fish)
• Clearcutting: Direct, Short-term Effects

  • Flooding and Landslides
  • Logging machinery compacts soil
  • Increased sunlight dries out soil (runoff >>> landslides)
  • Loss of root structure = erosion of topsoil and O-Horizon
  • All of these factors decrease H20 Holding Capacity of soil causing floods and landslides
• Tree Plantations

  • Areas where the same tree species are repeatedly planted, grown, and harvested

  
• Tree Plantation Effects

  • Lowers Biodiversity
  • Biodiverse, mature forests are replaced with single species
  • Less species diversity = lower ecological resilience
  • Less habitat diversity for other organisms
• Tree Plantation Effects

  • All the Same Age
  • All trees are planted at the same time
  • Lowers biodiversity further (no dead trees for woodpeckers, insects, decomposers)
• Forest Benefits

  • to understand the long-term effects of clearcutting, we must understand the benefits of forests
  • Filtering Air Pollutants
  • Stomata (leaf pores) remove VOCs, NO2, and particulate matter from air and store in tree or soil
• Forest Benefits

  • Removal, Sequester, and Storage of CO2
  • Trees sequester CO2 from the atmosphere and convert it and store it as sugar, wood, other tissue and release CO2
• Forest Benefits

  • Habitat for Organism
  • Many organisms live in forests
  • Biodiversity and ecological resilience
  • Humans have financial benefits
  • Ecotourism
• Long-term Consequences: Clearcutting

  1. Reduces air filtering and carbon-storing services
  2. Cutting trees down releases CO2 from the decomposition of leftover organic material
  3. Contributes to climate change
  4. Slash and Burn
• Slash and Burn

  • The method of clearing land for agriculture by cutting trees and burning them releases CO2, N2O, and water vapor into the atmosphere (all greenhouse gases)
• The Green Revolution

  • Shift in agricultural away from small, family operated forms to large, industrial scale agribusiness
• Green Revolution: Outcomes

  • Greatly increases effiency of lands, short-term profitability and food supply
  • Decreases world hunger and increased earth's carrying capacity for humans
  • Brings negative consequences (soil erosion, biodiversity loss, ground and surface water contamination)
• Mechanization

  • Increased use of tractors for plowing and tilling fields and combines for harvesting = increased yield = profits
  • Increases reliance on fossil fuels (gas/diesel fuel)
  • Emits greenhouse gases to atmosphere, leading to climate change
• Mechanization

  • Heavy machinery also compacts soil, decreasing H20 holding capacity
  • Dry soil is most easily blown by the wind or washed away by the rain (soil erosion)
• High-yield Variety (HYV) Crops

  • Hybrid or genetically modified crops that produce a higher yield (amount of crop produced per unit of area)
  • Hybrid = cross-pollinating different species or parent plants with ideal traits
  • Increased yield and food stability in regions previously prone to famine (India, Pakistan, Mexico)
  • GMOs = crops w/ new genes "spliced" in genomes
• GMOs

  • Genetically modified crops have genes for drought tolerance, pest resistance, faster growth, and larger unit fruit/grain
  • Increases profitability with fewer plants lost to drought, disease, or pests
  • Larger plants and yield/acre
  • Genetically identical, so genetical diversity is decreased and susceptibility to disease or pest (more vulnerable)
• Synthetic Fertilizers

  • Shift from organic fertilizers (like manure and compost) to synthetic fertilizers (man made ammonium, nitrate, phosphate)
  • Increases yield and profits with more key nutrients needed for plant growth (N,P,K) added to soil
• Synthetic Fertilizers

  • Excess nitrates and phosphates were washed off fields into nearby waters where they cause eutrophication
  • Require fossil fuels for production, releasing CO2 (climate change)
• Irrigation

  • Drawing water from the ground or nearby surface waters and distributing it on fields to increase plant growth
• Irrigation: Pros

  • Make agriculture possible in many parts of the world that are naturally too dry as they don't receive enough rain
• Irrigation: Cons

  • Can deplete groundwater sources, especially aquifers
  • Over-watering can drown roots (No O2 access) and cause soil salinization
• Soil Salinization

  • Soil salinization is the buildup of salt in the soil over time.
  • Salinization can be caused by excessive irrigation
• Pesticides

  • Increase in use of synthetic pesticides chemicals sprayed on crops that kills weeds, insects, rodents, and other pests that eat or damage crops
  • Increases yield and profits with fewer plants lost to pests
• Pesticides

  • Can wash off crops in runoff and kill or harm non-target species in local soil or waters (bees especially)
  • DDT (pesticide) thinned shells of bird eggs, especially eagles
  • Atrazine (pesticide) turns amphibians and fish intersex and sterile
• Monocropping

  • Growing one single species of crop
  • Highly efficient for harvest, pesticide, and fertilizer application for the SHORT TERM
• Monocropping: Cons

  • Greatly decreases biodiversity (more prone to pests, fewer natural predators)
  • Increases soil erosion (crops harvested all at one will leave soil bare)
  • Decreases habitat diversity for species living in the area (only 1 species)
• Tiling

  • Mixing and breaking up soil to make planting easier
  • Also loosens soil for roots
• Tiling: Cons

  • Increases soil erosion by loosening topsoil, breaking up leftover root structure from harvest
  • Loss of organic matter and topsoil nutrients over time
  • Increases particulate matter (respiratory irritation) and sediments in nearby water (turbidity)