IB DP Environmental Systems and Societies – Perspectives, systems and sustainability Study Guide

This study guide teaches the foundation unit of IB Diploma Programme Environmental Systems and Societies (ESS), aligned to the International Baccalaureate Organization Diploma Programme Subject Brief, Environmental systems and societies, first assessment 2026. It covers syllabus sections 1.1 Perspectives, 1.2 Systems and 1.3 Sustainability. The foundation unit is the starting point for both SL and HL, so everything here applies to both levels. 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.

Use it with the revision notes and the practice questions. For the whole course, see the ESS course hub and the printable checklist. The shorter Topic 1 Foundations overview gives the core definitions; this guide adds worked calculations and models.

What this unit covers

The brief gives the foundation unit 16 recommended teaching hours, the same for SL and HL.

Syllabus section	What you must be able to do	Hours	SL/HL
1.1 Perspectives	Explain what shapes an environmental value system (EVS); place people and policies on the EVS spectrum with evidence; explain how events change perspectives	3	SL and HL
1.2 Systems	Model a system with storages, flows and boundaries; tell transfers from transformations; explain equilibrium, feedback, tipping points and resilience; judge the strengths and limits of models	5	SL and HL
1.3 Sustainability	Use natural capital and natural income; classify ecosystem services; use footprints and biocapacity; apply planetary boundaries, doughnut economics and the circular economy; outline an environmental impact assessment	8	SL and HL

The brief says the three key concepts — perspectives, systems and sustainability — are integrated throughout the course and given special focus in this unit. Expect to reuse them in every later topic.

1.1 Perspectives

Perspectives, worldviews and value systems

A perspective is how a person sees a particular issue. It grows out of a wider worldview: the set of beliefs and values through which someone makes sense of the world. An environmental value system (EVS) is the part of that worldview that shapes how a person or group sees and judges environmental issues.

You can model an EVS as a system:

• Inputs: upbringing, culture, religion, education, media, economic position, personal experience.
• Processing: the person’s values and beliefs.
• Outputs: decisions, votes, purchases, lifestyle choices and the way they argue about an issue.

The EVS spectrum

EVSs are usually shown as a spectrum:

• Ecocentric (nature-centred). Nature has value in its own right. Deep ecologists put nature ahead of people. Self-reliance “soft ecologists” favour small, local communities that use fewer resources.
• Anthropocentric (people-centred). The environment should be managed for human benefit. Environmental managers accept limits, regulation and taxes as a way to protect resources for people.
• Technocentric (technology-centred). Human ingenuity and technology will solve environmental problems. Cornucopians see resources as effectively unlimited because new technology will always find more.

Most people sit somewhere along the spectrum, not at one end. Their position can differ from issue to issue.

How events change perspectives

Perspectives change as societies react to events and evidence. Standard examples:

• Rachel Carson’s book Silent Spring (1962) raised public concern about pesticide effects on wildlife.
• The Chernobyl nuclear accident (1986) changed attitudes to nuclear power in many countries.
• The Montreal Protocol (1987) showed that countries could agree to phase out ozone-depleting substances.
• The UN adopted 17 Sustainable Development Goals (SDGs) in 2015.

Indigenous knowledge systems often treat people as part of nature, caring for land and water across generations.

Worked example: placing stakeholders on the spectrum

Original scenario written for Marlbridge. A council plans a solar farm on 40 hectares of hay meadow.

• A farmer says: “The land feeds my family. I will lease it if the rent beats hay.” — Anthropocentric: the land is valued for the income it brings people.
• An engineer says: “New panels on raised frames let sheep graze underneath, so we lose nothing.” — Technocentric: trusts a technical design to remove the conflict.
• A local group says: “The meadow has orchids found nowhere else in the county. It should stay as it is.” — Ecocentric: the meadow has value in itself, whatever its use to people.

Each label is justified by the words used.

1.2 Systems

Parts of a system

A system is a set of connected parts that work together. Every system model needs:

• a boundary (what is inside the system);
• storages (stocks) of matter or energy, drawn as boxes;
• flows into, out of and within the system, drawn as arrows. Arrow width can show flow size.

Flows are of two kinds:

• A transfer moves matter or energy without changing its form or state (water flowing downstream; carbon in grass eaten by a cow).
• A transformation changes form or state (evaporation; photosynthesis turning light energy into chemical energy).

Systems can be open (energy and matter cross the boundary — most ecosystems), closed (energy crosses but matter does not — Earth is close to this) or isolated (neither crosses — no natural example exists). Systems exist at every scale, from a leaf to the biosphere.

Worked example: a storage and its flows

Fictional data. Lake Varn stores 1,200 million m³ of water. Yearly flows (million m³):

Inputs		Outputs
River inflow	310	River outflow	290
Rain on the lake	45	Evaporation	70
Groundwater seepage	25	Abstraction for a town	35

Total inputs  = 310 + 45 + 25 = 380 million m3 per year
Total outputs = 290 + 70 + 35 = 395 million m3 per year
Net change    = 380 - 395 = -15 million m3 per year
After 10 years (same flows): 1200 - 10 x 15 = 1050 million m3
Yearly loss as % of storage: 15 / 1200 x 100 = 1.25 %

Outputs exceed inputs, so the lake is not in steady state. It shrinks each year. Evaporation is a transformation (liquid to gas); river outflow and abstraction are transfers.

Models

A model is a simplified version of reality: a diagram, a physical model, an equation or a computer simulation. Lovelock’s Gaia hypothesis, for example, models the whole Earth as one self-regulating system.

• Strengths: make complex systems easier to understand; let you predict what happens when inputs change; can be tested and improved.
• Limitations: leave things out; rest on assumptions that may be wrong; can give different results from different starting data; accuracy falls the further ahead you predict.

Equilibrium and feedback

• Steady-state equilibrium: an open system keeps a roughly constant state while inputs and outputs continue. It fluctuates around an average (a mature forest).
• Static equilibrium: nothing changes over time. It applies to non-living systems, such as a rock on a slope.
• Stable equilibrium: after a disturbance, the system returns to its old state. Unstable equilibrium: it moves to a new state.

Negative feedback reduces a change and keeps a system stable. A rise in prey leads to more predators, which then brings prey numbers back down. Positive feedback amplifies a change and moves the system away from its old state. Warming melts sea ice; darker water absorbs more sunlight; warming increases. “Negative” and “positive” describe the direction of the effect, not whether it is good or bad.

Tipping points and resilience

A tipping point is a threshold. Past it, a small change causes a large and often long-lasting shift to a new state. Positive feedback usually drives the shift. They are hard to predict because little may change before the threshold.

Resilience is a system’s ability to absorb a disturbance and keep its state. Resilience tends to increase with diversity and with large storages. A species-rich forest recovers from a storm more easily than a single-species plantation. Human activity can lower resilience, for example by removing species or shrinking storages.

Emergent properties appear only at the level of the whole system, such as the stability of a whole food web.

1.3 Sustainability

Natural capital and natural income

Sustainability means using resources in a way that meets present needs without reducing the ability of future generations to meet theirs. The Brundtland Report (1987) made the linked idea of sustainable development widely known.

• Natural capital is the stock of natural resources (a forest, a fish stock, soil, an oil field).
• Natural income is the yield from that stock that can be taken each year without reducing it.

Renewable natural capital regrows; non-renewable capital (fossil fuels, metal ores) does not, so any use depletes it.

Worked example: is this harvest sustainable?

Fictional data. A community woodland holds 48,000 m³ of timber. It grows by 3.5% of its stock each year. The community cuts 2,100 m³ a year.

Natural income  = 48000 x 0.035 = 1680 m3 per year
Harvest - income = 2100 - 1680 = 420 m3 per year above income
Stock after 1 year = 48000 + 1680 - 2100 = 47580 m3
Harvest as % of income = 2100 / 1680 x 100 = 125 %

The harvest eats into the capital, so it is not sustainable. The largest sustainable harvest this year is 1,680 m³.

Ecosystem services and the three pillars

Natural capital supplies ecosystem services:

• Provisioning: products such as food, timber and fresh water.
• Regulating: control of processes, such as flood control, pollination and climate regulation.
• Cultural: recreation, spiritual and educational value.
• Supporting: processes the others depend on, such as soil formation and nutrient cycling.

Sustainability has environmental, social and economic pillars. A plan that protects a river but ruins local jobs is not sustainable in all three.

Measuring impact

• Ecological footprint (EF): the area of land and water needed to supply a population’s resources and absorb its wastes, in global hectares (gha).
• Biocapacity: the area actually available to do this.
• If EF is larger than biocapacity, there is an ecological deficit; if smaller, an ecological reserve.
• Carbon footprint: total greenhouse gas emissions caused by a person, product or country, in tonnes of CO₂ equivalent.
• Water footprint: total volume of fresh water used, directly and indirectly.

Fictional data. Country P has EF 4.8 gha per person, biocapacity 2.0 gha per person, population 12 million.

Deficit per person = 4.8 - 2.0 = 2.8 gha
Total deficit = 2.8 x 12 million = 33.6 million gha
EF / biocapacity = 4.8 / 2.0 = 2.4

Country P uses 2.4 times what its own land and water can supply, so it depends on imports or runs down its own capital.

Global models

• Planetary boundaries (Rockström and colleagues, 2009; names since updated): nine Earth-system processes, including climate change, biosphere integrity, land-system change, freshwater change, biogeochemical flows (nitrogen and phosphorus), ocean acidification, aerosol loading, stratospheric ozone depletion and novel entities. Crossing a boundary raises the risk of tipping points.
• Doughnut economics (Kate Raworth): an inner ring, the social foundation (food, water, health, education), and an outer ring, the ecological ceiling (based on planetary boundaries). The goal is the “safe and just space” between them.
• Circular economy: design out waste, keep products and materials in use, and regenerate natural systems. It replaces the linear “take, make, throw away” model.

Environmental impact assessment (EIA)

An EIA is carried out before a major development is approved. The usual stages: a baseline study of the site; prediction of likely impacts; mitigation measures to reduce them; a report with a non-technical summary; a decision; and monitoring after the project starts. Limits: predictions are uncertain, baseline data may be short-term, and the decision may still favour economic gain.

Common errors

• Calling worsening conditions “positive feedback” because the outcome is bad. Check whether the change is being amplified.
• Calling evaporation a transfer. A change of state is a transformation.
• Mixing up steady-state and static equilibrium. Living systems are in steady state.
• Stating “unsustainable” without comparing the harvest with natural income in numbers.
• Leaving units off footprint answers (gha, gha per person, t CO₂e).
• Naming an EVS without quoting evidence from the scenario.

Next steps

Test yourself with the practice questions, then use the revision notes in the final weeks. For the exam papers, read the exam preparation guide and the syllabus guide. Topic 2 follows in the Ecology study guide.

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.