Tragedy of the commons — overexploitation of a shared, unregulated resource.
Clearcutting — removing all trees from an area at once.
Monoculture — growing a single crop species over a large area.
Soil salinization — salt buildup in soil from irrigation evaporation.
Integrated pest management (IPM) — combining multiple pest-control strategies to reduce chemical use.
CAFO — Concentrated Animal Feeding Operation.
Bycatch — unintentional capture of non-target species while fishing.
Urban heat island effect — cities running warmer than surrounding rural areas.
Ecological footprint — land/resources needed to support consumption and absorb waste.
Sustainability — meeting present needs without compromising future generations.
Key themes to remember
Every land/water use method has a tradeoff. Higher yield or efficiency almost always comes with an environmental cost (erosion, water use, emissions).
The tragedy of the commons explains many of the unit's core problems. Overfishing, overgrazing, and deforestation all follow this pattern.
Intensification (Green Revolution, CAFOs) boosts output but increases input dependency. More fertilizer, water, and fossil fuel use accompanies higher yields.
Sustainable alternatives generally trade efficiency for lower environmental impact. IPM, selective cutting, and smart growth all sacrifice some output/density for reduced harm.
Urbanization concentrates environmental effects spatially. Heat islands and impervious surfaces are localized but significant impacts.
Common exam traps
Don't assume "more regulation = always better." Exam questions often test the specific mechanism (e.g., why IPM reduces pesticide resistance), not just "it's more sustainable."
Surface mining ≠ subsurface mining impacts. Surface mining destroys more habitat; subsurface mining is more dangerous for workers and risks subsidence.
Drip irrigation is efficient but expensive to install — don't describe it as a free or simple fix for water-stressed farms.
CAFOs are efficient per-animal but produce concentrated waste — don't conflate "efficient" with "low environmental impact."
Smart growth ≠ no growth. It's about directing growth to be more compact and efficient, not stopping development.
The tragedy of the commons requires the resource to be both shared AND unregulated. A privately owned or well-regulated resource doesn't fit the model.