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AP Environmental Science Unit 5 Visual Review

A 17-slide visual walkthrough of every Topic 5.1-5.17 concept — the tragedy of the commons, land use practices, agriculture, irrigation, meat and fish production, mining, urbanization, and sustainability — built right into the page.

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TOPIC 5.1 The Tragedy of the Commons shared, unregulated pasture each herder adds "one more" — the field can't recover The core logic Each individual gets the FULL benefit of adding one more animal, but the COST of overgrazing is shared among everyone. That mismatch pushes rational individuals toward overexploitation. Fixes: privatize, regulate, or cooperate Assign private property rights, impose catch limits/permits, or build community agreements with real enforcement. Real examples: fisheries quotas, public grazing permits, carbon markets. Overfishing (5.8), clearcutting (5.2), and groundwater depletion are all real-world tragedies of the commons. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.2 Clearcutting Clearcut all trees removed at once Selective cutting only mature trees removed Clearcutting's impacts Removes ALL trees at once — cheapest, fastest harvest method. But bare soil erodes fast, habitat disappears overnight, and losing the canopy disrupts the local water cycle (less transpiration). Selective cutting's tradeoff Removing only some trees preserves canopy cover, habitat, and soil stability — but it's slower and more expensive per unit of timber harvested — the sustainability tradeoff (5.17). Bare, clearcut slopes lose topsoil to erosion far faster than a forest can regenerate it. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.3 The Green Revolution crop yield per acre 1950 → 2000s HYV seeds introduced Three ingredients High-yield varieties (HYVs) — crops bred for maximum output. Synthetic fertilizer — Haber-Bosch nitrogen (recall Topic 1.5) at massive scale. The tradeoff Prevented mass famine and fed billions more people — but locked farming into heavy fossil fuel use, irrigation demand, fertilizer runoff (eutrophication, 1.6), and reduced crop genetic diversity through monoculture (5.4). More calories per acre came at the cost of more fossil-fuel dependence per calorie. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.4 Impacts of Agricultural Practices Monoculture One crop, one field. Efficient to plant/harvest, but low genetic diversity invites pests & disease. Tillage Turning soil loosens it for planting, but leaves it bare and exposed — accelerates erosion (4.2). Fertilizer & pesticides Boost yield, but runoff causes eutrophication (1.6) and pesticides can harm pollinators & biomagnify. The common thread Each of these practices maximizes short-term yield at some longer-term environmental cost — soil health, water quality, or biodiversity. Sustainable agriculture (5.15) exists specifically to reduce these tradeoffs through crop rotation, no-till farming, and reduced chemical inputs. Every intensive farming technique trades some future soil, water, or biodiversity for present yield. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.5 Irrigation Methods Flood Cheapest, but ~50% efficient — most water is lost to evaporation & runoff. High salinization risk. Spray ~75-85% efficient. Sprinklers/center-pivot; still loses water to wind drift & evaporation. Drip Most efficient (~90%+) — water delivered right to the root. Expensive to install & maintain. Salinization: the shared risk Irrigation water always carries trace dissolved salts. As water evaporates from the field, those salts stay behind and build up in the soil over years — eventually making the land toxic to most crops. Flood irrigation, with the most standing water and evaporation, carries the highest salinization risk of the three methods. Salinized land can take decades — or extensive flushing with fresh water — to become productive again. Efficiency and cost trade off directly: drip saves the most water but costs the most to install. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.6 Pest Control Methods Chemical pesticides IPM (5.14) Biological control ← fast, broad, high resistance risk slower, targeted, self-sustaining → Chemical pesticides Fast and effective short-term, but pests evolve resistance over time (natural selection, 2.6), can kill beneficial insects and pollinators, and can biomagnify up the food chain. Biological control Introducing a natural predator or pathogen of the pest. Self-sustaining and chemical-free — but a poorly chosen introduced species can itself become invasive. IPM (Topic 5.14) sits deliberately in the middle — combining tools instead of picking just one extreme. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.7 Meat Production Methods resource use per lb of meat CAFO land CAFO feed+GHG free-range land range feed+GHG CAFOs (feedlots) Concentrated Animal Feeding Operations use very little LAND per animal, but require heavy grain feed inputs, produce concentrated waste runoff, and pack animals in disease-prone density. Free-range / grass-fed Uses far more LAND per animal (grazing area), but spreads waste naturally and needs less grain input. Cattle still emit methane either way — a major greenhouse gas source. There's no free lunch: CAFOs trade land for concentrated pollution; free-range trades efficiency for land. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.8 Impacts of Overfishing fish stock time → healthy → declining → collapse stock collapse Beyond maximum sustainable yield Fishing faster than a population can reproduce shrinks the breeding stock, so future catches keep falling — even with the same effort. See Topic 5.12 for the maximum sustainable yield. Ripple effects Bycatch — unwanted species caught and discarded, often dead, alongside the target catch. Trophic cascades — removing a predator or key species reshuffles the entire food web (1.11). Overfishing is the textbook tragedy of the commons (5.1) — the ocean is shared and historically unregulated. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.9 Impacts of Mining surface mining (removes land/habitat entirely) subsurface mining (tunnels — less surface disturbance) acid drainage → Surface mining destroys more habitat directly; subsurface mining risks collapse & deep water contamination. Acid mine drainage: exposed sulfide minerals react with air & water to form sulfuric acid, which leaches toxic metals into streams — often for decades after a mine closes. Reclamation laws now require restoring mined land — but acid drainage can persist long after mining stops. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.10 Impacts of Urbanization temperature urban core (heat island) rural rural Urban heat island effect Pavement and buildings absorb and re-radiate heat, while little vegetation is left to cool the air through transpiration (1.7). Cities can run several degrees warmer than surrounding land. Impervious surfaces Roads and roofs block infiltration, so rainwater becomes fast, polluted runoff (4.6) instead of soaking into groundwater. Topic 5.13 covers specific fixes for this exact problem. Urban sprawl compounds both problems at once — more pavement means more heat AND more runoff. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.11 Ecological Footprints footprint (global hectares) Earth's biocapacity Bangladesh world avg USA Qatar What it measures The land and water area needed to produce everything a person consumes AND absorb all the waste they generate — measured in "global hectares." Overshoot Humanity's total footprint currently EXCEEDS Earth's biocapacity — we use resources faster than they regenerate. Footprints vary hugely by country, driven mainly by wealth and fossil-fuel consumption, not just population. A wealthy nation's per-person footprint can be 10x a developing nation's — consumption drives the number more than headcount. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.12 Introduction to Sustainability Environment Economy Society sustainable Definition Meeting present needs WITHOUT compromising future generations' ability to meet theirs. Requires balancing environmental, economic, AND social needs together. Maximum sustainable yield (MSY) The largest harvest (of fish, timber, etc.) that can be taken INDEFINITELY without shrinking the resource — set right at the population's fastest-growth point, roughly half of K (3.4). True sustainability needs all three circles — environmental protection alone isn't sustainable if it bankrupts a community. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.13 Methods to Reduce Urban Runoff standard pavement all water runs off fast permeable pavement water soaks through to soil Green infrastructure toolkit Rain gardens — shallow, planted depressions that catch and filter runoff on-site. Retention/detention ponds — hold stormwater temporarily, releasing it slowly to prevent flooding. Green roofs — vegetation on rooftops absorbs rain before it ever reaches street level. Every method here does the same job traditional soil once did — let water soak in instead of racing off. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.14 Integrated Pest Management chemical (last resort) biological controls mechanical / physical monitoring & prevention (first) Start at the base, escalate up IPM begins with monitoring pest levels and prevention (crop rotation, resistant varieties), then adds mechanical traps or barriers, then biological controls — chemicals only if needed. Why it works By combining methods rather than relying on one, IPM reduces overall pesticide use, slows the evolution of pesticide resistance, and protects beneficial insects like pollinators. IPM isn't a single method — it's a decision-making hierarchy that reaches for chemicals last, not first. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.15 Sustainable Agriculture Crop rotation Alternating crops restores soil nutrients & breaks pest/disease cycles. No-till farming Leaves soil undisturbed — cuts erosion & preserves soil structure & carbon. Contour plowing Plowing along the slope's contour lines slows water runoff & erosion downhill. More sustainable practices Cover crops — planted between growing seasons to keep soil covered and add organic matter. Terracing — steps carved into steep slopes to slow runoff on hillside farms. Windbreaks — rows of trees that reduce wind erosion across open fields. All of these directly counter the erosion mechanisms introduced back in Topic 4.2. None of these techniques are new inventions — they're older methods intensive agriculture (5.3-5.4) moved away from. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.16 Aquaculture fish/shellfish pen or pond waste & excess feed The upside Farming fish and shellfish takes fishing pressure OFF wild stocks (5.8), provides a reliable protein supply, and can be more land- and water-efficient than land-based meat (5.7). The downside Dense pens concentrate waste and excess feed, polluting surrounding water. Escaped farmed fish can spread disease to, or interbreed with, wild populations nearby. Farming carnivorous fish (like salmon) can actually strain wild stocks further — they're fed wild-caught fishmeal. The Review Hub · AP Environmental Science Unit 5 TOPIC 5.17 Sustainable Forestry Selective cutting Remove only mature trees, preserving canopy and habitat structure — the direct alternative to 5.2. Reforestation Replanting harvested areas restores canopy over time, but a planted stand rarely matches old-growth diversity. Prescribed burns Controlled fires clear underbrush & recycle nutrients (recall 2.5), preventing worse wildfires. The certification connection Programs like the Forest Stewardship Council (FSC) certify timber harvested using these practices, giving consumers a way to choose wood products that keep forests functioning as habitat and carbon sinks (1.4) rather than being permanently converted to other land uses. A working forest and a healthy forest aren't opposites — sustainable forestry tries to keep both true at once. The Review Hub · AP Environmental Science Unit 5
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How to use the visual review

Spend 30 seconds per slide before clicking next. Look at the diagram, then ask yourself: "Could I draw this from memory and explain it?"

Use the fullscreen button () on desktop for the best experience. Use arrow keys to navigate. Tap "Show all slides" to jump around.

This covers every one of Unit 5's 17 CED topics, from the tragedy of the commons through sustainable forestry.