Land and Water Use — AP Environmental Science Unit 5 practice.
This unit covers agriculture, forestry, urbanization and water management — essential concepts for AP Environmental Science. Use our interactive study games to test your understanding, or review questions in traditional format below.
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This unit covers agriculture, forestry, urbanization and water management — essential concepts for AP Environmental Science. Use our interactive study games to test your understanding, or review questions in traditional format below.
Key Concepts Breakdown
1 Agriculture
Students must understand the environmental impacts of different agricultural practices, including soil degradation, water use, and pollution. Know the differences between sustainable and conventional farming methods and how each affects ecosystems. The AP exam frequently tests cause-and-effect relationships between farming practices and environmental consequences.
Key Points
- Monocultures increase vulnerability to pests and disease, reduce biodiversity, and deplete specific soil nutrients faster than polycultures
- Overuse of synthetic fertilizers causes eutrophication in downstream water bodies via nutrient runoff (nitrogen and phosphorus)
- Irrigation accounts for ~70% of global freshwater withdrawals; flood irrigation is least efficient, drip irrigation is most efficient
- Slash-and-burn agriculture releases CO2, destroys habitat, and causes short-term soil fertility followed by rapid degradation
A farmer in the Midwest grows only corn on 500 acres year after year, applies nitrogen fertilizer heavily, and uses flood irrigation from a nearby river. What are two likely environmental consequences?
The nitrogen fertilizer runs off into streams and eventually into the Gulf of Mexico, fueling algal blooms that deplete oxygen and create a hypoxic dead zone. The flood irrigation withdraws large volumes of river water inefficiently, potentially lowering river levels and harming aquatic habitats downstream.
2 Forestry
Students must know the differences between clear-cutting, selective cutting, and sustainable forestry, and the ecological consequences of each. Understand how deforestation affects the carbon cycle, water cycle, and biodiversity. The exam tests both the problems caused by deforestation and the solutions provided by sustainable forest management.
Key Points
- Clear-cutting removes all trees, causing soil erosion, increased runoff, loss of habitat, and disruption of the water cycle (less transpiration)
- Old-growth forests store significantly more carbon than plantations or secondary-growth forests
- The CITES treaty and national forest policies regulate logging; certification programs (e.g., FSC) promote sustainable sourcing
- Deforestation contributes approximately 10–15% of global greenhouse gas emissions annually
After a timber company clear-cuts a hillside forest, a nearby stream's turbidity increases dramatically and salmon populations decline. Explain the chain of events causing this outcome.
Without tree root systems, soil on the hillside is no longer held in place, so rainfall carries large amounts of sediment into the stream, increasing turbidity. High turbidity blocks sunlight needed by aquatic plants, clogs salmon gills, and smothers gravel spawning beds, leading to reproductive failure and population decline.
3 Urbanization
Students must understand how urban growth changes land use, alters local hydrology through impervious surfaces, and creates environmental problems like urban heat islands and increased stormwater runoff. Know the difference between urban sprawl and smart growth strategies. The exam tests both the problems of urbanization and evidence-based solutions.
Key Points
- Impervious surfaces (roads, parking lots, rooftops) prevent infiltration, increase surface runoff speed and volume, and raise flood risk
- Urban heat islands form because dark paved surfaces absorb more solar radiation and vegetation that provides evaporative cooling is removed
- Urban sprawl increases per-capita resource use, habitat fragmentation, and vehicle miles traveled compared to dense urban design
- Green infrastructure solutions (permeable pavement, green roofs, urban trees) reduce runoff and mitigate heat island effects
A city replaces a 10-acre forest with a shopping mall and parking lot. What happens to the local water cycle, and what is one measurable environmental consequence?
The forest previously absorbed rainfall through infiltration and returned water vapor to the atmosphere via transpiration; the impervious surfaces of the mall and parking lot now redirect that same rainfall as rapid surface runoff into storm drains. This increases peak flood levels in nearby streams and reduces groundwater recharge, potentially lowering the local water table.
4 Water Management
Students must understand how humans manage freshwater resources through dams, reservoirs, water diversion projects, and groundwater extraction, and the ecological trade-offs involved. Know the causes and consequences of water scarcity and the difference between surface water and groundwater systems. The exam tests both the benefits of water infrastructure and its environmental costs.
Key Points
- Dams provide flood control, hydroelectric power, and irrigation water but block fish migration, alter downstream sediment flow, and flood upstream habitats
- Groundwater overdraft (pumping faster than recharge) causes aquifer depletion, land subsidence, and saltwater intrusion in coastal areas
- The Ogallala Aquifer supplies ~30% of U.S. groundwater for irrigation but is being depleted far faster than it recharges (recharge rate ~1 inch/year)
- Desalination produces freshwater from seawater but is energy-intensive and produces hypersaline brine discharge harmful to marine ecosystems
A region relies on a large dam for irrigation. Over decades, farmers downstream notice their fields receiving less water and the river delta is eroding. What explains these changes?
The dam traps sediment that would naturally flow downstream, starving the delta of the material it needs to maintain its structure against erosion. Additionally, as the reservoir fills with trapped sediment over time, its water storage capacity decreases, reducing the volume available for downstream irrigation.
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What is Land and Water Use?
Land and Water Use is Unit 5 of AP Environmental Science, covering agriculture, forestry, urbanization and water management.
How to study for AP Environmental Science Unit 5?
Start with the Quick Summary above, review the Key Concepts, then test yourself with our interactive study games. Aim for 80%+ accuracy before moving on.
How many questions are in this unit?
This unit has 30+ review questions across 5 different game modes.