Unit 5: Land and Water Use
AP Environmental Science: 52 practice questions with detailed explanations.
Unit Study Guide
Executive Summary
Unit 5 examines how humans use land and water — agriculture, meat production, mining, logging, and cities — and how to make those uses sustainable.
Tragedy of the commons
Shared resources (fisheries, pastures, air) degrade when individuals act in self-interest without regulation or privatization. Hardin's framework explains overfishing and overgrazing.
Agriculture
The Green Revolution boosted yields via synthetic fertilizer, irrigation, pesticides, and high-yield varieties — at the cost of water depletion, soil degradation, and pollution. Modern methods: monocropping, tilling, GMOs, and feedlots. Alternatives: crop rotation, cover crops, no-till, integrated pest management (IPM), and organic farming.
Irrigation and water
Flood, furrow, drip, and spray irrigation trade cost against efficiency — drip loses the least water. Over-irrigation causes waterlogging and salinization; aquifers like the Ogallala are being mined faster than they recharge.
Meat and food
Feedlots (CAFOs) concentrate animals and waste; free-range uses more land. Meat production is far more resource-intensive per calorie than plants. Aquaculture supplies fish but can pollute and spread disease.
Mining and logging
Surface mining (strip, open-pit, mountaintop removal) scars land; subsurface mining is dangerous. The Surface Mining Control and Reclamation Act requires restoration. Clear-cutting erodes soil; selective cutting and shelterwood methods preserve more habitat.
Urbanization and footprint
Cities create heat islands, impervious surfaces, and runoff. The ecological footprint measures the land needed to support a lifestyle; sustainability means living within Earth's biocapacity.
Exam traps
IPM uses chemicals as a last resort, not never. The Green Revolution raised yields but did not solve hunger everywhere. Drip irrigation is efficient but expensive — tradeoffs, not absolutes.