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AP Environmental Science · Unit 5 of 9
Land & Water Use
10–15% of the exam4 lessons · 50 min20 terms
What this unit covers
The topics below follow the published Env. Science course framework for Unit 5. This unit is worth 10–15% of the exam, so budget your time against that rather than against how long the unit takes to teach.
AgricultureMiningOverfishingUrbanization
Lessons in this unit
- Agriculture & Feeding the World13 min · 3 objectivesDescribe the trade-offs of the Green Revolution and industrial agriculture · Compare irrigation methods and explain how they lead to soil salinization · Calculate the percent change in crop yield from agricultural data
- Mining & Resource Extraction12 min · 3 objectivesDistinguish surface mining methods from subsurface mining · Explain the environmental impacts of mining, including acid mine drainage · Calculate the mass of metal recoverable from ore of a given grade
- Fishing & Overharvesting12 min · 3 objectivesExplain the tragedy of the commons using fisheries as an example · Describe overfishing, bycatch, and the promise and problems of aquaculture · Apply the concept of maximum sustainable yield to a fishery
- Urbanization & Ecological Footprints13 min · 3 objectivesDescribe urban sprawl and its environmental consequences · Explain how impervious surfaces alter local hydrology and heat · Interpret ecological footprint data to judge whether resource use is sustainable
Formulas in Unit 5
Percent change in yield
percent change = [(new value − old value) / old value] × 100
A positive result is an increase, a negative result a decrease. Always divide by the ORIGINAL (old) value, not the new one.
Metal recovered from ore
mass of metal = mass of ore × (ore grade as a decimal)
Ore grade is the percent of the ore that is the target metal. Convert the percent to a decimal (0.5% = 0.005) before multiplying.
Maximum sustainable yield
sustainable harvest ≤ number of new individuals added per period
The maximum sustainable yield is the largest catch that can be taken repeatedly without shrinking the population. Harvest above the replacement rate and the stock declines toward collapse.
Ecological balance
footprint > biocapacity → ecological deficit (overshoot) · footprint < biocapacity → reserve
Compare demand (footprint) to supply (biocapacity). A footprint larger than the available biocapacity means resources are being drawn down faster than they regenerate.
Every term in Unit 5
All 20 terms we publish for Land & Water Use, with definitions. Reading them through is the fastest way to find the ones you cannot define — then drill those in cram mode until you can produce them without the prompt.
- Tragedy of the commons
- A shared, unregulated resource is overused because each user gains the whole benefit while sharing the cost — the model behind overfishing and air pollution.
- Clearcutting
- Removing all trees in an area. Fast and cheap, but causes erosion, habitat loss, higher stream temperature and reduced water quality.
- Green revolution
- High-yield crop varieties with heavy irrigation, fertilizer and pesticide use. Raised yields substantially while increasing water use and runoff.
- Monoculture
- Growing one crop over a large area. Efficient to plant and harvest, but vulnerable to a single pest and depleting to soil nutrients.
- Irrigation methods
- Flood irrigation is cheap but wasteful and causes salinization; drip irrigation delivers water at the root and is the most efficient.
- Salinization and waterlogging
- Repeated irrigation leaves dissolved salts as water evaporates, and excess water raises the water table into the root zone.
- Integrated pest management
- Combines biological controls, crop rotation, targeted pesticide use and monitoring, reducing pesticide volume and resistance.
- Pesticide resistance
- Survivors of a treatment reproduce, so the pest population becomes resistant. The pesticide selects for it; it does not create it.
- Concentrated animal feeding operations
- Produce meat cheaply but concentrate waste, require antibiotics that drive resistance, and contaminate nearby water.
- Overfishing and bycatch
- Harvesting faster than stocks reproduce; bycatch is the non-target species caught and discarded, often including turtles and dolphins.
- Aquaculture trade-offs
- Reduces pressure on wild stocks but concentrates waste, spreads disease to wild populations, and often requires wild-caught fish as feed.
- Urban sprawl
- Low-density development that increases car dependence, impervious surface and runoff while consuming farmland.
- Urban runoff and impervious surface
- Pavement prevents infiltration, so rainfall runs off carrying oil, metals and nutrients directly into waterways, and causes flash flooding.
- Sustainable practices
- Crop rotation, no-till farming, contour plowing, terracing, windbreaks, cover crops and rotational grazing all conserve soil.
- Desertification
- Productive drylands degrading to desert through overgrazing, deforestation and poor irrigation. Roughly a third of global land is at risk.
- Maximum sustainable yield
- The largest harvest that can be taken indefinitely, occurring near half the carrying capacity where population growth rate is fastest.
- Terracing and contour plowing
- Terracing cuts steps into slopes and contour plowing follows elevation lines; both slow runoff and reduce erosion.
- Windbreaks and cover crops
- Rows of trees slow wind erosion; cover crops hold soil between plantings and add organic matter when tilled in.
- Mining methods and impacts
- Surface and strip mining remove overburden and cause severe habitat loss and acid mine drainage; subsurface mining is safer for land but far more dangerous for miners.
- Acid mine drainage
- Exposed sulfide minerals react with water and oxygen to form sulfuric acid, which lowers stream pH and mobilises heavy metals.
What examiners penalize here
- For percent-change problems, the number-one error is dividing by the new value instead of the old. Anchor on "change ÷ original × 100." And remember: a doubling is +100%, a tripling is +200% — the increase is one less multiple than the factor of growth.
- For ore-grade calculations, convert the percentage to a decimal before multiplying (0.5% → 0.005). Then notice the waste-to-product ratio — AP loves to ask you to interpret how much waste rock is generated, which ties the math directly to the environmental impact.
- For maximum sustainable yield questions, compare the harvest rate to the reproduction (replacement) rate. Harvest ≤ replacement is sustainable; harvest > replacement causes decline. Numbers make it concrete — always state whether the catch is above or below the yearly recruitment.
- For ecological footprint questions, the rule is simple: footprint > biocapacity = deficit/overshoot (unsustainable); footprint < biocapacity = reserve (sustainable). Dividing footprint by biocapacity gives the overshoot factor, a common follow-up calculation.
Practice Env. Science
Our practice bank is drawn from across the whole course rather than filtered to one unit, which is closer to how the exam asks anyway — it will not tell you which unit a question is testing.
Questions about this unit
How much of the AP Environmental Science exam is Unit 5?
Unit 5, Land & Water Use, is worth 10–15% of the Env. Science multiple-choice section according to the published course framework. Across all 9 units that makes it a substantial share — heavier than an even split would give it.
What topics are covered in Env. Science Unit 5?
Land & Water Use covers Agriculture, Mining, Overfishing and Urbanization. We publish 20 terms with definitions for this unit, all of them on this page.
How should I study Env. Science Unit 5?
Read the 4 lessons below first — about 50 minutes — then drill the 20 terms in cram mode until you can produce each definition from memory rather than just recognize it. Recognition is what makes a unit feel finished when it is not. Finish with practice questions and read the explanation for every one you get right by elimination as well as the ones you miss.
All 9 units of AP Environmental Science
Unit names, topics and exam weights follow the published College Board course framework for AP Environmental Science. AP® is a trademark registered by the College Board, which does not endorse this site.