Unit 5 Tragedy of the commons Tap / Space to flip
Unit 5 Shared resources (atmosphere, oceans, grazing land) are over-exploited because individuals gain while costs are diffused.
Unit 5 · 10–15% of exam
Land and Water Use
Tragedy of the commons, agriculture, irrigation, mining, urbanization. Heavy on tradeoffs and sustainable practices.
Must-know content
- Tragedy of the commons — shared resources (atmosphere, oceans, grazing land) are overexploited because individuals reap private gain while diffuse costs are shared.
- Agriculture:
- Green Revolution (1940s–60s): high-yield crop varieties, synthetic fertilizers, pesticides, irrigation. Tripled yields but expensive in water and chemical inputs.
- Monoculture — single crop over a wide area. Boosts yield but leaves crops vulnerable to pests and disease.
- GMOs — engineered for traits (Bt corn, Roundup Ready). Yield gains; concerns about biodiversity and resistance.
- CAFOs — concentrated animal feeding operations. High productivity but manure waste, methane, antibiotic resistance, water pollution.
- Irrigation methods (most → least water-efficient): drip > furrow > spray > flood. Side effects: salinization (salt buildup from evaporation), waterlogging, aquifer depletion.
- Sustainable agriculture: contour plowing, terracing, no-till, crop rotation, cover crops, agroforestry, integrated pest management (IPM).
- Pesticides & the "pesticide treadmill": repeated use selects for resistance, requiring stronger chemicals.
- Mining:
- Surface — open-pit, strip, mountaintop removal. Cheaper but devastates landscape, pollutes streams.
- Subsurface — less damage on surface but dangerous to workers (cave-ins, black lung).
- Urbanization: impervious surfaces increase runoff & flooding; urban heat islands (cities warmer than surrounding rural land); urban sprawl consumes habitat.
- Overfishing: bottom trawling, ghost nets, bycatch. Fish populations collapsing globally.
- Aquaculture — fish farming. Reduces wild-fish pressure but creates nutrient pollution and disease.
- Ecological footprint — land/water needed to support a person\'s consumption. Wealthy nations have higher per-capita footprint.
Example questions
MCQ Which irrigation method is MOST water-efficient? (A) Flood (B) Furrow (C) Drip (D) Spray
Answer: C. Drip irrigation delivers water directly to the root zone via tubing, minimizing evaporation and runoff. Flood is the worst — most water evaporates or runs off.
FRQ Describe ONE environmental impact of mountaintop removal mining and propose a solution.
Answer: Impact: removed rock and soil ("overburden") is dumped into adjacent valleys, burying headwater streams and increasing sediment and heavy-metal pollution downstream. Aquatic communities are smothered, and water quality drops for downstream users. Solution: enforce strict Surface Mining Control and Reclamation Act (SMCRA) compliance — companies must restore the original landscape contour, replant native vegetation, and treat any acid-mine drainage. Where feasible, transition to underground (subsurface) mining instead, or reduce demand by improving energy efficiency and substituting renewables for coal.
MCQ Which of the following is the MOST effective way to reduce soil erosion on a sloped farm field? (A) Plowing up and down the slope (B) Contour plowing along elevation lines (C) Removing all vegetation (D) Switching to monoculture
Answer: B. Contour plowing follows natural elevation lines, slowing water flow and reducing soil loss. Plowing up-and-down a slope creates channels for water to scour the field.
Drill flashcards
Unit 5 Green Revolution Tap / Space to flip
Unit 5 1940s-60s expansion of high-yield crop varieties, synthetic fertilizers, pesticides, and irrigation. Increased yields but environmental cost.
Unit 5 CAFO Tap / Space to flip
Unit 5 Concentrated Animal Feeding Operation. High productivity but creates manure waste, methane, antibiotic resistance, water pollution.
Unit 5 Irrigation issues Tap / Space to flip
Unit 5 Salinization (salt buildup from evaporation), waterlogging, aquifer depletion, lower water tables.
Unit 5 Clear-cutting Tap / Space to flip
Unit 5 Removes all trees in an area at once. Cheap & efficient but causes soil erosion, habitat loss, sediment runoff.
Unit 5 Surface vs. subsurface mining Tap / Space to flip
Unit 5 Surface (strip, mountaintop removal) cheaper but devastates landscape. Subsurface less damaging on surface but more dangerous to workers.
Unit 5 IPM Tap / Space to flip
Unit 5 Integrated Pest Management. Combines biological, mechanical, and chemical controls to minimize pesticide use.
Unit 5 Overfishing Tap / Space to flip
Unit 5 Catching faster than fish can reproduce. Bycatch, bottom trawling, and ghost nets compound the damage.