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Revision Notes

IB Environmental Systems & Societies HL

Every topic of the ESS course, including the Higher Level topics on environmental law, economics and ethics — written for the syllabus with first examinations in 2026.

ESS HL · Revision Notes

Table of Contents

Click any topic to expand, then open a sub-topic to see its notes. Notes tagged HL are Higher Level only, as is everything in topics 9–11.

11topics39sub-topics231revision notes119HL only
1

Foundations

Thinking in systems: perspectives, inputs and outputs, and what sustainability actually means.

16 notes▾
1.1

Perspectives

4▾
What Shapes a Perspective→ How Values Shape Environmental Views→ Worldviews and the Environment→ The Rise of the Environmental Movement→
1.2

Systems

5▾
Thinking in Systems→ Open, Closed and Isolated Systems→ Equilibrium and Feedback Loops→ Resilience and Tipping Points→ Using Models in ESS→
1.3

Sustainability

7▾
What Sustainability Means→ Sustainable Development and the SDGs→ Environmental Justice and Equity→ Measuring Sustainability with Indicators→ Citizen Science and Public Data→ Frameworks for Sustainable Thinking→ Rethinking Economic Models→
2

Ecology

Populations, energy flow, nutrient cycles, biomes, and how ecosystems change over time.

43 notes▾
2.1

Individuals, Populations, Communities & Ecosystems

10▾
How Ecological Systems Fit Together→ Classifying Species and Using Keys→ What Controls Population Size→ Patterns of Population Growth→ Human Populations in Ecosystems→ Sampling and Studying Populations→ How Ecosystems Keep Functioning→ HLBuilding a Modern Classification System→ HLThe Niche a Species Could Fill, and the One It Does→ HLLife Cycles and Survivorship Curves→
2.2

Energy & Biomass in Ecosystems

13▾
Following Energy Through an Ecosystem→ Photosynthesis as an Energy Input→ Respiration and Energy Release→ Trophic Levels and Feeding Chains→ Building and Reading Food Webs→ Why Energy Is Lost at Each Level→ Biomass and Productivity→ Drawing Ecological Pyramids→ How Humans Disrupt Energy and Matter Flow→ HLHow Organisms Obtain Their Energy→ HLCalculating Primary and Secondary Productivity→ HLMaximum Sustainable Yield→ HLMeasuring Ecological Efficiency→
2.3

Biogeochemical Cycles

7▾
Nutrient Cycles in Ecosystems→ Carbon Stores and Flows→ How Humans Alter the Carbon Cycle→ Cutting Our Impact on the Carbon Cycle→ HLWhere Carbon Is Stored→ HLThe Nitrogen Cycle→ HLHow We Disrupt the Nitrogen Cycle→
2.4

Climate & Biomes

6▾
Weather Versus Climate→ Global Biomes and Their Distribution→ Circulating Air and Ocean Currents→ HLClassifying the World’s Climates→ HLEl Niño and the Southern Oscillation→ HLTropical Cyclones in a Warming World→
2.5

Zonation, Succession & Change

7▾
Zonation Along Environmental Gradients→ Succession and How Communities Change→ What Makes an Ecosystem Stable→ HLWhat Drives Succession→ HLHow Productivity Changes Through Succession→ HLr and K Reproductive Strategies→ HLClimax Communities and Arrested Succession→
3

Biodiversity & Conservation

What biodiversity is worth, what is destroying it, and how it can be protected and rebuilt.

30 notes▾
3.1

Biodiversity & Evolution

11▾
Biodiversity and Ecosystem Resilience→ How Evolution Generates Diversity→ Measuring Biodiversity→ Managing Biodiversity in Practice→ HLGenetic Diversity Within Species→ HLReproductive Isolation and Speciation→ HLWhat Makes a Biodiversity Hotspot→ HLHow Humans Redirect Evolution→ HLReading the Geological Timescale→ HLThe Five Mass Extinctions→ HLThe Anthropocene→
3.2

Human Impact on Biodiversity

9▾
What Is Driving Species Loss→ Judging Conservation Status→ Case Studies in Decline and Recovery→ Shared Resources and the Tragedy of the Commons→ HLPressures on Biodiversity Hotspots→ HLIdentifying Key Biodiversity Areas→ HLIndigenous Land Management→ HLConservation and Environmental Justice→ HLLosing Biosphere Integrity→
3.3

Conservation & Regeneration

10▾
Why Preserving Biodiversity Matters→ Approaches to Conservation→ Designing and Managing Protected Areas→ Rewilding and Regeneration→ Biodiversity as a Planetary Boundary→ Competing Views on Conservation→ HLWho Actually Does Conservation Work→ HLRestoring Habitats Through Rewilding→ HLJudging Whether Conservation Worked→ HLEcotourism as a Conservation Tool→
4

Water

Freshwater and ocean systems, water security, aquatic food production and pollution.

33 notes▾
4.1

Water Systems

6▾
How Water Moves Around the Planet→ How Humans Change the Water Cycle→ HLWhy Water Behaves the Way It Does→ HLOceans as a Carbon Sink→ HLWhy Water Forms Layers→ HLUpwelling and Ocean Circulation→
4.2

Water Access, Use & Security

7▾
What Decides Who Gets Water→ Ways to Increase Water Supply→ Tackling Water Scarcity→ HLHow the World Uses Fresh Water→ HLWhat Causes Water Stress→ HLResponding to Water Stress→ HLFairness in Water Access→
4.3

Aquatic Food Production Systems

10▾
Food Webs in Aquatic Systems→ Rising Demand for Seafood→ Overfishing and Damaging Harvest Methods→ Protecting Fish Stocks→ Aquaculture and Fish Farming→ Warming Seas and Ocean Acidification→ HLNutrients and Productivity in the Oceans→ HLMeasuring a Fish Stock→ HLBringing Depleted Stocks Back→ HLThe Rules and Ethics of Fishing→
4.4

Water Pollution

10▾
Where Water Pollution Comes From→ Plastics in Aquatic Systems→ Testing and Monitoring Water Quality→ Eutrophication and Its Consequences→ Managing Water Pollution→ HLWhat Good Water Quality Looks Like→ HLHow Sewage Is Treated→ HLBiotic and Abiotic Water Quality Indicators→ HLStandards for Drinking Water→ HLCutting Water Pollution at Source→
5

Land

Soil as a living system, and how agriculture feeds a growing population without exhausting the ground it stands on.

19 notes▾
5.1

Soil

6▾
What Soil Is Made Of→ How Soil Behaves and What It Does→ HLReading a Soil Profile→ HLWhat Shapes a Soil→ HLSoil Texture, Structure and Composition→ HLSoil as a Carbon Store→
5.2

Agriculture & Food

13▾
Land Use and Farming Systems→ Traditional Versus Industrial Farming→ Protecting and Restoring Soil→ How Sustainable Is Our Food System→ Food Security and Access→ HLWhy Farmers Farm the Way They Do→ HLAlternatives to Industrial Farming→ HLRegenerative Farming→ HLNew Technology in Farming→ HLHow Sustainable Is Your Diet?→ HLHarvesting Wild Food Sustainably→ HLLow-Productivity Food Systems→ HLDistribution, Food Quality and Malnutrition→
6

Atmosphere & Climate Change

Atmospheric structure, greenhouse gases, the impacts of a warming climate, and the response to them.

29 notes▾
6.1

Introduction to the Atmosphere

7▾
What the Atmosphere Is Made Of→ How the Greenhouse Effect Works→ HLHow the Atmosphere Moves→ HLHow the Atmosphere Changes With Altitude→ HLMilankovitch Cycles→ HLHothouse Earth→ HLHow Life Changed the Atmosphere→
6.2

Climate Change: Causes & Impacts

8▾
Atmospheric Processes That Drive Climate→ What Is Causing Climate Change→ Climate Change and Ecosystems→ Climate Change and Human Societies→ HLMonitoring the Climate→ HLHow Climate Models Work→ HLClimate Tipping Points→ HLWho Caused It and Who Suffers→
6.3

Climate Change: Mitigation & Adaptation

8▾
Global Agreements and Decarbonisation→ Mitigating Climate Change→ Adapting to a Changing Climate→ HLChoosing How to Respond to Climate Change→ HLEmissions Scenarios and What They Show→ HLGeoengineering the Climate→ HLWhy Climate Intervention Is Hard→ HLCompeting Views on Climate Action→
6.4

Stratospheric Ozone

6▾
Ultraviolet Radiation and Living Things→ Ozone in the Stratosphere→ The Montreal Protocol and Ozone Recovery→ HLHow Ozone Is Destroyed→ HLWhy the Hole Forms Over the Poles→ HLCFCs, HCFCs and Their Replacements→
7

Natural Resources

Renewable and non-renewable resources, energy security, and what happens to everything we throw away.

19 notes▾
7.1

Natural Resources: Uses & Management

8▾
Treating Nature as Capital→ Putting a Value on Natural Capital→ Using Resources Sustainably→ Resource Security and the Choices Behind It→ HLDrawing Down Natural Capital→ HLEnvironmental Impact Assessments→ HLWhen Renewable Resources Run Out→ HLSecuring Natural Resources→
7.2

Energy Sources: Uses & Management

7▾
Energy Sources and How Sustainable They Are→ Energy Demand and the Choices We Make→ Storing and Saving Energy→ HLWhat Energy Security Means→ HLFossil Fuel Reserves and Peak Oil→ HLNuclear Power: Costs and Benefits→ HLStoring Energy in Batteries→
7.3

Solid Waste

4▾
What Counts as Waste→ The Cost of Waste to People and Ecosystems→ How Waste Is Disposed Of→ Managing and Reducing Waste→
8

Human Populations & Urban Systems

Population dynamics, urbanisation, and the environmental cost of city living.

19 notes▾
8.1

Human Populations

7▾
How Human Populations Change→ Managing Population Growth→ Population Structure and Models→ HLPopulation Growth and Environmental Pressure→ HLDependency Ratios and Population Momentum→ HLGlobal Population Patterns→ HLEnvironmental Migration→
8.2

Urban Systems & Urban Planning

7▾
What Makes an Area Urban→ Why Cities Grow→ Urban Sprawl and Expansion→ Planning Sustainable Cities→ HLDesigning Cities as Ecosystems→ HLModels of Urban Sustainability→ HLGreen Architecture→
8.3

Urban Air Pollution

5▾
Where Urban Air Pollution Comes From→ Cleaning Up Urban Air→ Acid Deposition and Its Effects→ HLHow Photochemical Smog Forms→ HLThe Damage Done by Tropospheric Ozone→
9

Environmental Law HL

The rules that govern how we use natural systems, and whether they work.

8 notes▾
9.1

Introduction to Environmental Law

2▾
HLWhat Environmental Law Is For→ HLEnvironmental Justice and Its Obstacles→
9.2

Legal Frameworks & Governance

3▾
HLEnvironmental Rights in Constitutions→ HLLocal, National and International Law→ HLInternational Law and Cooperation→
9.3

Application & Enforcement

3▾
HLEnvironmental Law in the Courts→ HLMaking Environmental Protection Stronger→ HLCombining Legal and Economic Tools→
10

Environmental Economics HL

Costs, values and growth — and everything the market leaves out.

8 notes▾
10.1

Introduction to Environmental Economics

1▾
HLWhat Environmental Economics Is For→
10.2

Market Failures & Solutions

2▾
HLMarket Failure and How to Fix It→ HLGreenwashing and the Commons Problem→
10.3

Environmental Accounting & Valuation

1▾
HLPutting a Price on the Environment→
10.4

Economic Growth & Impacts

2▾
HLWhat Economic Growth Measures→ HLThe Environmental Cost of Growth→
10.5

Ecological Economics

2▾
HLEcological Economics→ HLDoughnut and Circular Economic Models→
11

Environmental Ethics HL

How we decide what we owe to nature, to each other and to future generations.

7 notes▾
11.1

Introduction to Environmental Ethics

1▾
HLWhat Environmental Ethics Is For→
11.2

Ethical Frameworks

2▾
HLFrameworks for Ethical Decisions→ HLInstrumental and Intrinsic Value→
11.3

Ethical Approaches

3▾
HLVirtue Ethics→ HLConsequentialist Ethics→ HLRights-Based Ethics→
11.4

Environmental & Social Justice Movements

1▾
HLEnvironmental and Social Justice Movements→

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