Topic 1: Foundation

1.1 Perspectives

1.2 Systems

1.3 Sustainability

Topic 2: Ecology

2.1 Individuals, populations, communities, and ecosystems

2.2 Energy and biomass in ecosystems

2.3 Biogeochemical cycles

2.4 Climate and biomes

2.5 Zonation, succession and change

Topic 3: Biodiversity and conservation

3.1 Biodiversity and evolution

3.2 Human impact on biodiversity

3.3 Conservation and regeneration

Topic 4: Water

4.1 Water systems

4.2 Water access, use and security

4.3 Aquatic food production systems

4.4 Water pollution

Topic 5: Land

5.1 Soil

5.2 Agriculture and food

Topic 6: Atmosphere and climate change

6.1 Introduction to the atmosphere

6.2 Climate change—causes and impacts

6.2.1—Climate definition

6.2.2—Anthropogenic CO₂ emissions

6.2.3—Ice core, tree ring, sediment data

6.2.4—Enhanced greenhouse effect

6.2.5—Climate change impacts on ecosystems

6.2.6—Climate change impacts on societies

6.2.7—Climate change models

6.2.8—Climate change planetary boundary

6.2.9—Perspectives on climate change

6.2.10 (HL)—Climate data collection

6.2.11 (HL)—Global climate models

6.2.12 (HL)—Climate model scenarios

6.2.13 (HL)—Critical thresholds and tipping points

6.2.14 (HL)—Tipping cascades

6.2.15 (HL)—Climate justice

6.3 Climate change—mitigation and adaptation

6.4 Stratospheric ozone

Topic 7: Natural resources

7.1 Natural resources—uses and management

7.2 Energy sources—uses and management

7.3 Solid waste

Topic 8: Human populations and urban systems

8.1 Human populations

8.2 Urban systems and urban planning

8.3 Urban air pollution

HL.a Environmental law

HL.b Environmental economics

HL.c Environmental ethics

IB ESS HL 6.2.13 (HL)—Critical thresholds and tipping points Question Bank

• Earth may approach critical threshold → new equilibrium

• Examples: Antarctic ice sheet melting, Atlantic circulation slowing, Amazon-Cerrado transition

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