IB DP Environmental Systems and Societies – Perspectives, systems and sustainability Revision Notes

For full explanations and worked examples, read the study guide first.

These revision notes cover the foundation unit of IB Diploma Programme Environmental Systems and Societies, aligned to the International Baccalaureate Organization Diploma Programme Subject Brief, Environmental systems and societies, first assessment 2026. They cover syllabus sections 1.1 Perspectives, 1.2 Systems and 1.3 Sustainability, which are common to SL and HL. It follows the IB ESS subject brief for first assessment 2026 — the course examined in the May and November 2026, 2027 and 2028 sessions.

The brief names Topic 1’s three subtopics (1.1 Perspectives, 1.2 Systems, 1.3 Sustainability) and gives Topic 1 16 teaching hours at SL and HL, but it sets out no learning outcomes, so the outcomes on this page, and any numbering below Topic 1’s three subtopics, follow the printable ESS checklist, not the brief itself.

Test yourself afterwards with the practice questions. Track your progress on the printable checklist and find every ESS page on the course hub. For a lighter recap of the same unit, see the Topic 1 Foundations revision notes; for paper formats, see the assessment revision notes.

The unit at a glance

• Foundation unit: 16 recommended hours in the brief — 1.1 Perspectives 3, 1.2 Systems 5, 1.3 Sustainability 8.
• Same content at SL and HL. The brief calls it the starting point for both courses.
• The three concepts (perspectives, systems, sustainability) are meant to be used in every later topic. Paper 1 gives you an unseen case study with data; this unit gives you the tools to analyse it.

1.1 Perspectives — key terms

Term	Meaning
Perspective	How a person sees one particular issue
Worldview	The wider set of beliefs and values used to make sense of the world
Environmental value system (EVS)	The worldview that shapes how a person or group sees and judges environmental issues
Ecocentric	Nature has value in itself (deep ecologists; self-reliance soft ecologists)
Anthropocentric	Manage nature for human benefit (environmental managers)
Technocentric	Technology will solve environmental problems (cornucopians)

EVS as a system: inputs (culture, religion, education, media, experience, economic position) → processing (values) → outputs (decisions, actions, arguments).

Events that shifted perspectives (use as examples): Silent Spring (1962), Chernobyl (1986), Montreal Protocol (1987), Brundtland Report (1987), UN SDGs (2015, 17 goals).

Method: labelling a stakeholder’s EVS

1. Find the stakeholder’s own words or actions in the source.
2. Ask: what do they value most — nature itself, human benefit, or a technical fix?
3. Name the EVS.
4. Quote the evidence and explain the link.
5. If the position is mixed, say where on the spectrum it sits and why.

1.2 Systems — key terms

Term	Meaning
System	Connected parts working together, with a boundary
Storage	A stock of matter or energy (box on a diagram)
Flow	Movement of matter or energy (arrow; width can show size)
Transfer	Flow with no change of form or state (river flow, grazing)
Transformation	Flow with a change of form or state (evaporation, photosynthesis, respiration)
Open / closed / isolated	Energy and matter cross / only energy crosses / neither crosses
Model	Simplified representation of a system
Steady-state equilibrium	Open system with continuing flows that fluctuates around an average
Static equilibrium	No change at all; non-living systems
Negative feedback	Reduces a change; stabilising
Positive feedback	Amplifies a change; destabilising
Tipping point	Threshold beyond which a small change causes a large, often long-lasting shift
Resilience	Ability to absorb disturbance and keep the same state
Emergent property	Property of the whole system, not of any single part

Method: storage calculations

1. Add all inputs. Add all outputs. Keep the units.
2. Net change per time = total inputs − total outputs.
3. New storage = old storage + (net change × number of time steps), if flows stay the same.
4. Net change = 0 means steady state for that storage.
5. State whether the storage is growing (sink) or shrinking (source).

Reminder (fictional): storage 1,200 units, inputs 380, outputs 395 per year → net −15 per year → 1,050 after 10 years.

Models — evaluation checklist. Strengths: simplify, predict, test, communicate. Limitations: omit factors, rest on assumptions, sensitive to input data, less accurate the further ahead they predict.

Resilience rises with: diversity (species, genes, habitats), large storages, fast recovery rates, and wide geographic range. Human activity can lower it.

1.3 Sustainability — key terms

Term	Meaning
Sustainability	Using resources to meet present needs without reducing the ability of future generations to meet theirs
Natural capital	Stock of natural resources
Natural income	Yield that can be taken from the stock each year without reducing it
Ecosystem services	Provisioning, regulating, cultural, supporting
Ecological footprint (EF)	Land and water area needed to supply a population and absorb its waste (gha)
Biocapacity	Land and water area actually available (gha)
Ecological deficit / reserve	EF > biocapacity / EF < biocapacity
Carbon footprint	Total greenhouse gas emissions (t CO₂e)
Water footprint	Total fresh water used, directly and indirectly
Planetary boundaries	Nine Earth-system limits (Rockström and colleagues, 2009)
Doughnut economics	Social foundation (inner) and ecological ceiling (outer); aim for the space between
Circular economy	Design out waste, keep materials in use, regenerate nature
EIA	Baseline → predict impacts → mitigation → report → decision → monitoring

Method: sustainable harvest

1. Natural income = stock × growth rate (or the regrowth figure given).
2. Compare harvest with natural income.
3. Harvest ≤ income: sustainable. Harvest > income: capital is being depleted.
4. New stock = stock + income − harvest.
5. Conclude in words, with the numbers.

Reminder (fictional): 48,000 m³ woodland growing 3.5% a year → income 1,680 m³; harvest 2,100 m³ is 420 m³ over income.

Three pillars: environmental, social, economic. A plan must be judged on all three.

Must-know distinctions

• Transfer vs transformation. Same form = transfer. New form or state = transformation.
• Steady-state vs static equilibrium. Flows continue vs nothing changes.
• Stable vs unstable equilibrium. Returns to the old state vs moves to a new one.
• Negative vs positive feedback. Direction of the effect, not good or bad.
• Natural capital vs natural income. Stock vs sustainable yield.
• Renewable vs non-renewable capital. Regrows vs any use depletes it.
• Ecological footprint vs carbon footprint. Area (gha) vs emissions (t CO₂e).
• Planetary boundaries vs doughnut. Environmental limits only vs environmental limits plus a social foundation.
• Tipping point vs resilience. The threshold itself vs the ability to stay away from it.

Quick self-test

1. A pond storage holds 500 units. Inputs are 80 units per year and outputs 95 units per year. What is the net change per year, and the storage after 4 years?
2. A fish stock of 20,000 t grows by 6% a year. The catch is 1,500 t a year. Is this sustainable? Give numbers.
3. A country has EF 3.0 gha per person and biocapacity 3.6 gha per person. Deficit or reserve, and how large?
4. A household of 4 has a carbon footprint of 26 t CO₂e a year. What is the footprint per person?
5. Classify evaporation of water from a lake: transfer or transformation?
6. A reservoir receives 36 units and loses 36 units each month. What does this tell you about the storage?
7. A politician says “new desalination plants mean we will never run short of water.” Which EVS?
8. Give one reason why a tipping point is hard to predict.
9. Classify pollination of crops by wild bees as an ecosystem service.
10. What does the inner ring of the doughnut economics model represent?

Answers

1. Net change = 80 − 95 = −15 units per year. After 4 years: 500 − 60 = 440 units.
2. Natural income = 20,000 × 0.06 = 1,200 t. The catch is 300 t above income, so it is not sustainable; the stock is being depleted.
3. Ecological reserve of 3.6 − 3.0 = 0.6 gha per person.
4. 26 ÷ 4 = 6.5 t CO₂e per person per year.
5. Transformation — liquid changes to gas.
6. Inputs equal outputs, so the storage is constant (steady state) for as long as the flows stay the same.
7. Technocentric — trusts technology to remove the limit.
8. Any one: the system may show little change before the threshold; positive feedback makes the shift sudden; many interacting factors; the threshold may only be known once crossed.
9. Regulating service.
10. The social foundation — basic human needs such as food, water, health and education.

Where marks are usually lost

• Writing “positive feedback” for any change that makes things worse, instead of checking whether the change is amplified.
• Calling evaporation, condensation or photosynthesis a transfer.
• Saying a harvest is “unsustainable” without calculating natural income and comparing.
• Dropping units in footprint answers, or mixing gha per person with total gha.
• Forgetting to multiply by population when a total deficit is asked for.
• Naming an EVS with no quotation or action from the source as evidence.
• Treating the EVS spectrum as three boxes; mixed positions should be placed and explained.
• Listing model strengths only when the command term is “evaluate”.
• Describing sustainability only in environmental terms, with no social or economic pillar.
• Calling an EIA a guarantee that harm will not happen; it predicts and reduces impacts.

Where to go next

Work through the practice questions, then check your exam technique with the exam preparation guide. The subject guide explains how the course fits together, and the Topic 2 Ecology revision notes come next.

Official syllabus

International Baccalaureate Organization, Diploma Programme Subject Brief, Environmental systems and societies, first assessment 2026. The brief lists subtopics for Topic 1 only; the subtopic numbering on this page follows the printable ESS checklist.