Unit 9: Global Change focuses on how human activities alter Earth’s systems on a large scale. On the APES exam, you’ll see climate-related FRQs, cause-and-effect chains, and global policy references.
This RevisionDojo review breaks down the essential knowledge for both MCQs and FRQs.
🌍 Key Topics in Unit 9
- Climate change and greenhouse gases
- Ozone depletion and CFCs
- Ocean acidification
- Invasive species
- Endangered species and biodiversity loss
- Overfishing and resource depletion
- Global treaties and policies
- Sustainability strategies
☁ Greenhouse Gases & Climate Change
Main GHGs: CO₂, CH₄ (methane), N₂O, CFCs
- Sources: Fossil fuel combustion, agriculture, industrial processes
- Impacts: Sea level rise, glacial melt, extreme weather, ecosystem shifts
Solutions:
- Renewable energy transition
- Energy efficiency
- Carbon sequestration
🌀 Ozone Depletion
- Cause: CFCs & halons → release chlorine atoms → destroy stratospheric ozone
- Impacts: More UV radiation → skin cancer, cataracts, ecosystem harm
- Solution: Montreal Protocol (1987) → phased out CFCs
🌊 Ocean Acidification
- CO₂ dissolves in seawater → forms carbonic acid → lowers pH
- Impacts: Coral bleaching, shellfish decline, food chain disruptions
🌱 Invasive Species
- Definition: Non-native species that outcompete native species
- Examples: Zebra mussels, cane toads, kudzu
- Control: Prevention, mechanical removal, biological control
🐟 Overfishing & Resource Depletion
- Causes: Technological advances, weak regulation
- Impacts: Population collapse, food web disruption
- Solutions: Catch limits, marine protected areas, sustainable seafood
📜 Key Global Policies
- Montreal Protocol – Ozone protection
- Kyoto Protocol – GHG reduction targets
- Paris Agreement – Global climate commitment
- CITES – Regulates trade in endangered species
🌱 Sustainability Strategies
- Reduce carbon footprint
- Protect biodiversity hotspots
- Promote circular economy principles
- Support sustainable agriculture
🧠 APES Exam Tips for Unit 9
- Always connect human activity → environmental impact → societal impact → solution.
- Be ready to cite specific international treaties and explain their purpose.
- Practice FRQs involving data interpretation for climate and biodiversity trends.
💡 FAQ – Unit 9: Global Change
Q: What’s the most effective treaty for ozone protection?
A: The Montreal Protocol.
Q: How does ocean acidification relate to CO₂ emissions?
A: More CO₂ in the air dissolves in oceans, lowering pH and harming marine life.
Q: Why are invasive species so damaging?
A: They often lack natural predators and outcompete native species for resources.
Final Word from RevisionDojo:
Unit 9 tests your ability to link global environmental issues with actionable solutions. Use real-world examples in FRQs to show depth in your answers.
