IB DP Environmental Systems & Societies

Sustainability

Subtopic 1.3 — New Syllabus (First Assessment 2026)
Standard Level + Higher Level

🌍

22 SL Syllabus Points

1.3.1 – 1.3.22

📊

Core Content Focus

Pillars, SDGs & Metrics

OVERVIEW

Guiding Question

Key Question: How can the interconnectedness of environmental, social, and economic systems help us understand sustainability?

Content Map

A. Sustainability
1.3.1 – 1.3.7

→

B. Measuring
Sustainability
1.3.8 – 1.3.13

→

C. Development
& SDGs
1.3.14 – 1.3.18

→

D. Models
1.3.19 – 1.3.22

Section	Syllabus Points	Focus
A	1.3.1–1.3.7	Defining sustainability, three pillars, their interconnections
B	1.3.8–1.3.13	Indicators, ecological footprint, HDI, GPI, Limits to Growth
C	1.3.14–1.3.18	Development vs. growth, SDGs, MDGs
D	1.3.19–1.3.22	I=PAT, nested model, circular economy, doughnut economy

1.3.1

Definition of Sustainability

Key Understanding: Sustainability involves maintaining the capacity of environmental, social, and economic systems to meet the needs of the present without compromising the ability of future generations to meet their own needs.

This is the widely cited Brundtland Definition, from the 1987 report Our Common Future by the World Commission on Environment and Development (WCED).

Element	Meaning
"Meet the needs of the present"	Current populations must have access to resources, food, water, shelter, and opportunities
"Without compromising… future generations"	Resource use today must not deplete or degrade the environment so that future people cannot meet their needs
"Environmental, social, and economic systems"	Sustainability is not only environmental — it encompasses all three pillars

💡 Exam Tip: When asked to define sustainability, always mention all three systems (environmental, social, economic) — not just environmental.

1.3.2

The Three Pillars of Sustainability

Key Understanding: Sustainability has three interconnected pillars: environmental, social, and economic. All three must be balanced for true sustainability. One cannot be achieved at the expense of others.

🌍 Environmental

👥 Social

💰 Economic

Pillar	Core Focus	Example Indicator
🌍 Environmental	Protection of natural systems, biodiversity, and resources	CO₂ emissions, biodiversity index
👥 Social	Equity, well-being, health, education, and justice	HDI, literacy rate, life expectancy
💰 Economic	Long-term viability of economic systems and livelihoods	GDP per capita, employment rate

⚠️ Common Mistake: Students often equate sustainability with only environmental issues. Always remember the three-pillar model — true sustainability requires balance.

1.3.3

Environmental Sustainability

Key Understanding: Environmental sustainability focuses on maintaining natural capital, biodiversity, and ecosystem services.

Key Concepts

Concept	Definition	Example
Carrying capacity	The maximum population size an environment can sustain indefinitely given available resources	Island ecosystem supporting a finite number of deer
Renewable resources	Resources that replenish on a human timescale	Solar energy, timber (if managed), freshwater
Non-renewable resources	Resources that exist in finite quantities and cannot be replaced within a human timescale	Fossil fuels, mineral ores, groundwater in aquifers
Ecosystem services	Benefits humans obtain from ecosystems	Pollination, water purification, carbon sequestration, flood control

Four Categories of Ecosystem Services (MEA Framework)

🌱 Provisioning
Food, water, timber

→

🔄 Regulating
Climate, floods, disease

→

🎭 Cultural
Recreation, spiritual

→

⚙️ Supporting
Nutrient cycling, soil

1.3.4

Social Sustainability

Key Understanding: Social sustainability focuses on maintaining social systems, equity, and well-being.

Key Concepts

Concept	Definition	Example
Social capital	The networks, norms, and trust that enable collective action in a community	Community cooperatives, mutual aid networks
Cultural diversity	The variety of cultural expressions within a society	Indigenous knowledge systems, language preservation
Health	Physical and mental well-being of a population	Access to healthcare, clean water, nutrition
Education	Access to quality learning opportunities	Literacy rates, school enrollment, gender parity in education
Justice	Fair treatment and equitable distribution of rights and resources	Gender equality, land rights, legal protections

💡 Exam Tip: Social sustainability is often the least discussed pillar. When analysing a case study, always consider social impacts — e.g., how does a mining project affect community health, education, and cultural practices?

1.3.5

Economic Sustainability

Key Understanding: Economic sustainability focuses on maintaining economic systems that can function long-term.

Key Concepts

Concept	Definition	Example
Economic growth	Increase in the production of goods and services (measured by GDP)	Country's GDP rising from $500B to $550B
Economic development	Improvement in quality of life, not just output — includes equity, health, education	Better healthcare, infrastructure, reduced poverty
Natural capital accounting	Assigning economic value to natural resources and ecosystem services	Valuing a mangrove forest for storm protection + fishery support
Circular economy	Economic system aimed at eliminating waste through continual resource use	Recycling electronics, remanufacturing tyres

⚠️ Key Distinction: Economic growth ≠ economic development. A country can have high GDP growth while poverty and inequality increase. Development encompasses broader well-being.

1.3.6

Interconnections Between the Pillars

Key Understanding: The three pillars are interconnected — changes in one affect the others.

Case Study: Deforestation in the Amazon

🌳 Environmental
Loss of biodiversity,
reduced carbon
sequestration

→

👥 Social
Displacement of
indigenous communities,
loss of livelihoods

→

💰 Economic
Short-term timber
revenue, but long-term
loss of ecosystem
services

Scenario	Environmental Effect	Social Effect	Economic Effect
Overfishing	Fish stock collapse, marine ecosystem degradation	Fishing communities lose livelihoods and food source	Fishery industry revenue declines
Fast fashion	Textile pollution, water contamination, microplastics	Exploitation of garment workers in developing countries	Low prices for consumers but externalised costs
Urbanisation	Habitat loss, urban heat island effect	Improved access to services but potential for slums	Higher productivity and GDP but infrastructure costs

1.3.7

Triple Bottom Line & Integration

Key Understanding: True sustainability requires integration of all three pillars. The concept of the "triple bottom line" — people, planet, profit.

The Triple Bottom Line (TBL), coined by John Elkington (1994), argues that organisations should measure success not just by financial profit, but also by their social and environmental impact.

TBL Dimension	Equivalent Pillar	Business Metric Example
🌿 Planet	Environmental	Carbon footprint, waste reduction, water use
👥 People	Social	Employee welfare, community investment, diversity
💵 Profit	Economic	Revenue, profitability, shareholder return

🌿 Planet

+

👥 People

+

💵 Profit

=

Sustainable Business

💡 Exam Tip: The TBL is excellent for business-related ESS questions. Example: "Evaluate the extent to which a TBL approach can ensure sustainability for a multinational corporation."

1.3.8

Measuring Sustainability — Indicators

Key Understanding: Sustainability can be measured using indicators. Different indicators cover the three pillars.

Pillar	Indicator	What It Measures	Strengths / Limitations
🌍 Environmental	CO₂ emissions (per capita)	Greenhouse gas output per person	Doesn't account for imports/exports of goods
	Biodiversity index	Species richness and abundance	Difficult to measure consistently across regions
	Deforestation rates	Area of forest lost per year	Doesn't distinguish between types of forest or causes
👥 Social	Human Development Index (HDI)	Life expectancy, education, income combined	Doesn't capture inequality within countries
	Literacy rate	% of population who can read/write	Binary measure — doesn't reflect quality of education
	Life expectancy	Average lifespan at birth	Doesn't capture quality of life or health equity
💰 Economic	GDP per capita	Average economic output per person	Doesn't account for wealth distribution or environmental costs
💰 Economic	Gini coefficient	Income inequality (0 = equal, 1 = unequal)	Doesn't capture wealth vs income or non-monetary factors

⚠️ Important: No single indicator can capture the full picture of sustainability. A combination of indicators across all three pillars is needed.

1.3.9

Ecological Footprint & Earth Overshoot Day

Key Understanding: Ecological footprint measures the amount of biologically productive land/water needed to support a population's consumption.

Ecological Footprint

Measured in global hectares (gha) — the area of biologically productive land needed to regenerate the resources a person/country consumes and absorb their waste.

Country / Region	Ecological Footprint (gha/person)	Biocapacity (gha/person)	Status
🇺🇸 United States	~8.1	~3.4	Overshoot (uses ~2.4× available)
🇨🇳 China	~3.7	~0.9	Overshoot (uses ~4.1× available)
🇮🇳 India	~1.2	~0.4	Overshoot (uses ~3.0× available)
🌍 World Average	~2.7	~1.6	Overshoot — we use ~1.7 Earths

Earth Overshoot Day

The date each year when humanity has used all the biological resources Earth can regenerate in that year. In 2023, it fell on 2 August.

📅 Jan 1
Earth's annual
resource budget
resets

→

⚠️ Aug 2
Earth Overshoot
Day 2023
Budget exhausted

→

❌ Aug 3 – Dec 31
Living on
"ecological debt"

💡 Exam Tip: Calculating an ecological footprint for a country given data is a common question type. Practice: "Using the data, calculate the ecological deficit/surplus for Country X."

1.3.10

Human Development Index (HDI)

Key Understanding: HDI combines life expectancy, education, and income. It's a broader measure than GDP alone.

Developed by Pakistani economist Mahbub ul Haq with input from Indian Nobel laureate Amartya Sen. Published annually by the UNDP.

Dimension	Indicator	Minimum	Maximum
Long and healthy life	Life expectancy at birth	20 years	85 years
Knowledge	Mean years of schooling + Expected years of schooling	0 years	18 years (mean) / 20 years (expected)
Decent standard of living	GNI per capita (PPP US$)	$100	$75,000

HDI Categories

Category	HDI Range	Example Countries
Very High	0.800 – 1.000	Switzerland (0.962), Norway (0.961), Iceland (0.959)
High	0.700 – 0.799	Russia (0.822), Brazil (0.760), China (0.768)
Medium	0.550 – 0.699	India (0.633), Kenya (0.575), Bangladesh (0.661)
Low	0.000 – 0.549	Chad (0.394), Niger (0.394), South Sudan (0.385)

⚠️ Limitations: HDI doesn't measure inequality (see Inequality-adjusted HDI), poverty, human security, or political freedom. GDP per capita within HDI may mask significant internal inequality.

1.3.11

Genuine Progress Indicator (GPI)

Key Understanding: GPI adjusts GDP by accounting for environmental costs and social factors. Can be negative when environmental/social costs exceed economic gains.

GPI starts with personal consumption expenditure (like GDP) and then adds value for household work, volunteering, and subtracts costs like crime, pollution, and resource depletion.

GPI = Personal Consumption + Non-market Benefits − Environmental & Social Costs

Factor	GDP Treatment	GPI Treatment
Household work / childcare	❌ Not counted	✅ Added as positive value
Volunteering	❌ Not counted	✅ Added as positive value
Pollution / environmental damage	❌ Not subtracted (may even add to GDP via cleanup)	✅ Subtracted as cost
Crime and family breakdown	❌ Not counted (may add to GDP via legal services)	✅ Subtracted as cost
Resource depletion	❌ Not subtracted	✅ Subtracted as cost
Income inequality	❌ Not accounted for	✅ Adjusted via distributional weighting

🔴 Key Point: In many developed countries, GPI peaked in the 1970s and has stagnated or declined since, even as GDP continued to rise. This suggests GDP growth has not translated into genuine well-being improvements.

1.3.12

Limits to Growth (Meadows et al., 1972)

Key Understanding: The Limits to Growth computer model predicted that unchecked population growth and resource consumption would lead to collapse.

Commissioned by the Club of Rome, this was one of the first major attempts to model global sustainability using computer simulations.

Key Model Variables

👥 Population

↔

🏭 Industrial
Output

↔

🌾 Food
Production

↔

⛏️ Non-renewable
Resources

↔

🏭 Pollution

Model Predictions (Business-as-Usual Scenario)

Variable	Behaviour
Population	Continues to grow until ~2040, then declines due to resource constraints
Food per capita	Peaks around 2020s, then declines sharply
Industrial output	Peaks and then falls as resources become scarce
Non-renewable resources	Continuously depleted, accelerating collapse
Pollution	Continues to rise even after industrial decline

⚠️ Debate: Critics argue the model oversimplifies and doesn't account for technological innovation. Supporters note that actual data through 2020 closely tracks the "business as usual" scenario. The model's core message — that infinite growth on a finite planet is impossible — remains widely accepted.

1.3.13 — HL

Quantitative vs. Qualitative Measurement (HL)

Key Understanding: Measuring sustainability requires considering both quantitative indicators and qualitative assessments. No single indicator captures full sustainability.

Type	Description	Examples	Strengths	Limitations
Quantitative	Numerical data that can be statistically analysed	HDI, CO₂ emissions, ecological footprint, Gini coefficient	Objectively comparable, trend tracking, policy evaluation	May miss cultural/contextual factors, data quality varies
Qualitative	Non-numerical assessments based on observation, interviews, case studies	Community well-being surveys, stakeholder interviews, cultural assessments	Captures nuance, local knowledge, cultural dimensions	Subjective, difficult to compare across regions, harder to scale

Multi-Indicator Approaches

Dashboard approach: Multiple indicators displayed together (e.g., OECD Better Life Index) — no single summary number
Composite indices: Combine multiple indicators into one score (e.g., HDI, GII) — easier to compare but loses detail
Systems thinking: Considers feedback loops and interconnections between indicators

💡 HL Exam Tip: Be prepared to critically evaluate which indicators are most appropriate for measuring sustainability in a given context. Discuss trade-offs between simplicity (composite indices) and comprehensiveness (dashboards).

1.3.14

What Is Development?

Key Understanding: Development is the process of improving quality of life. It includes economic growth, social progress, and environmental improvement.

Development goes far beyond GDP growth. It encompasses improvements in:

Dimension	Indicators	Examples
Economic	GDP per capita, employment, infrastructure	Roads, electricity access, industry diversification
Social	HDI, literacy, life expectancy, gender equality	Schools, hospitals, social safety nets
Environmental	Air quality, water quality, forest cover	Clean energy, waste management, conservation

⚠️ Development vs. Growth: Economic growth is a component of development, but not equivalent to it. A country can have high GDP growth with increasing poverty, pollution, and inequality — meaning development is not occurring.

1.3.15

Sustainable Development

Key Understanding: Sustainable development meets present needs without compromising future generations. Integration of economic growth, social inclusion, and environmental protection.

💰 Economic
Growth

+

👥 Social
Inclusion

+

🌍 Environmental
Protection

=

Sustainable
Development

Examples of Sustainable Development in Practice

Initiative	Economic	Social	Environmental
Costa Rica's payment for ecosystem services	Tourism revenue	Rural employment	Forest regeneration (doubled forest cover since 1980s)
Bhutan's GNH policy	Hydropower exports	Cultural preservation, free healthcare & education	Constitution mandates 60% forest cover forever
Copenhagen cycling infrastructure	Healthcare savings, tourism	Improved public health, equity in transport	Reduced emissions, less air pollution

1.3.16

UN Sustainable Development Goals (SDGs)

Key Understanding: The UN SDGs are 17 goals adopted in 2015 as a universal call to action to end poverty, protect the planet, and ensure peace and prosperity.

Adopted by all United Nations Member States in September 2015 as part of the 2030 Agenda for Sustainable Development.

#	Goal	#	Goal
1	🔴 No Poverty	10	🟡 Reduced Inequalities
2	🟡 Zero Hunger	11	🟠 Sustainable Cities & Communities
3	🟢 Good Health & Well-being	12	🟤 Responsible Consumption & Production
4	🔴 Quality Education	13	🟢 Climate Action
5	🔴 Gender Equality	14	🔵 Life Below Water
6	🔵 Clean Water & Sanitation	15	🟢 Life on Land
7	🟡 Affordable & Clean Energy	16	🔵 Peace, Justice & Strong Institutions
8	🔴 Decent Work & Economic Growth	17	🔵 Partnerships for the Goals
9. Industry, Innovation & Infrastructure

💡 Exam Tip: You don't need to memorise all 17 SDGs, but you should be able to name and explain 6–8 key goals and discuss how they interconnect (see 1.3.17).

1.3.17

SDG Interconnections

Key Understanding: The SDGs are interconnected — progress on one often affects others.

Example: How Clean Energy (SDG 7) Connects to Other Goals

⚡ SDG 7
Clean Energy

→

🌡️ SDG 13
Climate Action

→

🏭 SDG 9
Industry & Innovation

→

💼 SDG 8
Economic Growth

Primary Action	SDG	Positive Spillovers	Potential Tensions
Expanding solar energy	SDG 7	SDG 13 (less emissions), SDG 3 (less air pollution), SDG 8 (new jobs), SDG 9 (innovation)	SDG 15 (land use for solar farms may affect ecosystems), SDG 12 (mining for materials)
Improving sanitation	SDG 6	SDG 3 (fewer waterborne diseases), SDG 5 (women's safety), SDG 4 (girls attend school)	SDG 9 (cost of infrastructure), SDG 17 (needs international funding)
Reducing hunger	SDG 2	SDG 1 (less poverty), SDG 3 (better nutrition), SDG 4 (children can learn)	SDG 15 (agricultural expansion may cause deforestation), SDG 14 (overfishing)

🔴 Important: Some SDG actions can create trade-offs. For example, building dams can provide clean energy (SDG 7) but displace communities (SDG 1, SDG 10) and harm river ecosystems (SDG 14, SDG 15). Evaluating these tensions is essential.

1.3.18

Millennium Development Goals (MDGs) vs. SDGs

Key Understanding: MDGs (2000–2015) preceded the SDGs. They focused on developing countries. SDGs are universal and more comprehensive.

Feature	MDGs (2000–2015)	SDGs (2015–2030)
Number of goals	8	17
Scope	Mainly developing countries	Universal — all countries
Pillars covered	Mainly social and some economic	Environmental, social, and economic — all three pillars
Stakeholders	Primarily governments	Multi-stakeholder: governments, businesses, civil society, individuals
Environmental focus	Limited (only MDG 7: Environmental Sustainability)	Strong (SDGs 6, 7, 11, 12, 13, 14, 15)
Participation	Top-down from UN	Extensive global consultation process

MDG Successes and Failures

Success: Halved the proportion of people living in extreme poverty (MDG 1)
Success: Enrolment in primary education in developing countries increased from 83% to 91%
Failure: Goal to halve the proportion of people without safe drinking water was narrowly missed
Failure: Environmental sustainability (MDG 7) was largely not achieved

1.3.19

The I = PAT Equation

Key Understanding: I = PAT shows how human Impact depends on three factors: Population, Affluence, and Technology.

I = P × A × T

Variable	Meaning	Unit/Measure	Effect on Impact
I — Impact	Environmental impact (e.g., pollution, resource use, CO₂)	Varies (e.g., tonnes CO₂)	Dependent variable
P — Population	Number of people	Number of individuals	↑ more people = ↑ more impact
A — Affluence	Consumption per person	GDP per capita or resource use per capita	↑ more wealth/consumption = ↑ more impact
T — Technology	Impact per unit of consumption	Environmental impact per unit of GDP	↑ more efficient tech = ↓ impact; ↑ polluting tech = ↑ impact

Example Calculations

Country A
P = 100M
A = $5,000/capita
T = 0.5 kg CO₂/$

→

I = 100M × $5,000 × 0.5
= 250 million kg CO₂

Country B
P = 10M
A = $50,000/capita
T = 0.05 kg CO₂/$

→

I = 10M × $50,000 × 0.05
= 25 million kg CO₂

⚠️ Limitations: I=PAT assumes the factors are independent and equally weighted, which is not always the case. Technology can be both increasing impact (e.g., SUVs) and decreasing it (e.g., solar panels). The equation is a conceptual model, not a precise calculator.

1.3.20

The Ecological / Nested Model of Sustainability

Key Understanding: The ecological model considers how economic systems function within social systems, which function within environmental systems.

Three Nested Ellipses Model

This model shows that the economy is a subset of society, which is a subset of the environment. The environment is the largest and most fundamental system.

🌍 ENVIRONMENTAL SYSTEM

👥 SOCIAL SYSTEM

💰 ECONOMIC
SYSTEM

System	Contains	Dependency
🌍 Environment (outermost)	All natural resources, ecosystems, atmosphere	Self-sustaining (but vulnerable to damage)
👥 Society (middle)	Cultures, institutions, communities, governance	Depends entirely on the environment for resources and life support
💰 Economy (innermost)	Markets, trade, industry, financial systems	Depends on society for rules, labour, demand — and on the environment for raw materials and energy

💡 Key Difference from Three Pillars Model: The three pillars model shows them as equal and overlapping. The nested model argues that the economy is wholly contained within society and the environment — economic activity is impossible without a functioning society and a healthy environment.

1.3.21

Circular Economy

Key Understanding: The circular economy aims to eliminate waste by keeping resources in use for as long as possible. It contrasts with the linear economy.

Linear vs. Circular Economy

Linear Economy
Take → Make → Use → Dispose

Design Out Waste

→

Keep Products
in Use

→

Regenerate
Natural Systems

Three Principles of the Circular Economy

Principle	Description	Examples
1. Design out waste and pollution	Products designed from the start to minimise waste	Biodegradable packaging, modular electronics for easy repair
2. Keep products and materials in use	Extend product lifespan through repair, reuse, remanufacturing	Refurbished phones, clothing rental, car-sharing
3. Regenerate natural systems	Return biological nutrients to the earth; enhance rather than degrade ecosystems	Composting, reforestation, regenerative agriculture

Real-World Examples

Example	Sector	Circular Strategy
Patagonia	Clothing	Worn Wear programme — repair, reuse, resale of clothing
Fairphone	Electronics	Modular smartphone — replaceable parts, extended lifespan
Interface	Flooring	Carpet tiles designed for recycling; "Mission Zero" to eliminate waste
Kamikatsu, Japan	Waste management	Town with 45-category recycling system; near-zero waste

⚠️ Challenge: Transitioning to a circular economy requires systemic change — redesigning supply chains, changing consumer behaviour, and developing new business models. It is not just about recycling.

1.3.22 — HL

Critical Evaluation of Sustainability Models (HL)

Key Understanding: Critically evaluate different models of sustainability: the Brundtland model, three pillars, nested model, and doughnut economy. Each has strengths and limitations.

Model	Description	Strengths	Limitations
Brundtland Definition (1987)	"Meeting present needs without compromising future generations"	Widely accepted; intergenerational equity; holistic	Vague — "needs" and "future generations" not clearly defined; hard to operationalise
Three Pillars / Triple Bottom Line	Three overlapping circles: environmental, social, economic	Simple, intuitive; encourages balance; widely adopted in policy and business	Implies the three are equal — in reality, environment underpins the other two; can be used for "greenwashing"
Nested Model / Ecological Model	Economy within society within environment (concentric circles)	Correctly shows dependency — economy cannot exist without society and environment; emphasizes biophysical limits	May oversimplify the bidirectional influence between systems; less intuitive for business applications
Doughnut Economy (Kate Raworth, 2017)	A "safe and just space for humanity" between a social foundation (inner ring) and ecological ceiling (outer ring)	Balances social minimums with environmental maximums; visual and actionable; incorporates justice	Complex to measure all indicators simultaneously; doesn't fully address governance or geopolitical tensions

The Doughnut Economy Model — Visual

SAFE & JUST
SPACE FOR
HUMANITY

Outer ring (red): Ecological ceiling — planetary boundaries (e.g., climate change, biodiversity loss, ocean acidification)

Inner space (green): Social foundation — human needs (e.g., food, water, health, education, political voice)

Key Planetary Boundaries (Outer Ring of Doughnut)

Boundary	Status	Safe Limit
Climate change	Exceeded	350 ppm CO₂ (currently ~420 ppm)
Biosphere integrity (biodiversity loss)	Exceeded	<10 E/MSY
Nitrogen/phosphorus cycles	Exceeded	Industrial N fixation < 62 Tg N/yr
Ocean acidification	Near limit	≥ 80% of pre-industrial Ω aragonite
Freshwater use	Within bounds	< 4,000 km³/yr
Land-system change	Exceeded	< 75% forested land remaining

💡 HL Exam Tip: When asked to "critically evaluate" a sustainability model, you must discuss both strengths and limitations. Use specific examples. For example: "The three pillars model is widely used in business (strength) but may allow greenwashing because it treats economic and environmental concerns as equally important (limitation)."

GLOSSARY

Key Terms

Term	Definition
Sustainability	Maintaining the capacity of environmental, social, and economic systems to meet present needs without compromising future generations
Three Pillars	The environmental, social, and economic dimensions that together constitute sustainability
Natural Capital	The world's stocks of natural assets — geology, soil, air, water, and all living things — from which humans derive ecosystem services
Ecosystem Services	The benefits humans obtain from ecosystems: provisioning, regulating, cultural, and supporting services
Ecological Footprint	The area of biologically productive land and water required to produce resources consumed and absorb waste generated by a population
Earth Overshoot Day	The date each year when humanity's demand for ecological resources exceeds what Earth can regenerate in that year
HDI	Human Development Index — a composite measure of life expectancy, education, and income
GPI	Genuine Progress Indicator — adjusts personal consumption for environmental and social costs/benefits
SDGs	Sustainable Development Goals — 17 UN goals (2015–2030) for global sustainable development
MDGs	Millennium Development Goals — 8 UN goals (2000–2015) focused on reducing poverty in developing countries
I = PAT	Impact = Population × Affluence × Technology — equation showing drivers of environmental impact
Circular Economy	An economic system aimed at eliminating waste through continual use of resources (design out waste, keep in use, regenerate)
Triple Bottom Line	Framework measuring organisational success by People, Planet, and Profit (TBL)
Sustainable Development	Development that meets present needs without compromising the ability of future generations to meet their own needs
Doughnut Economy	Model by Kate Raworth defining a "safe and just space" between social foundation and ecological ceiling

EXAM TIPS

Exam Strategy & Command Terms

Command Terms for Subtopic 1.3

Command Term	What to Do	Example Question
Evaluate	Make a judgement supported by reasoning and evidence; discuss strengths and limitations	"Evaluate the effectiveness of the SDGs in achieving sustainable development."
Discuss	Present a balanced argument with multiple perspectives	"Discuss the extent to which economic growth is compatible with sustainability."
Explain	Give a detailed account with reasoning; show how/why something occurs	"Explain how the I=PAT equation can be used to analyse environmental impact."
Compare	Identify similarities and differences between two or more items	"Compare the three pillars model with the nested model of sustainability."

Common Question Patterns

💡 Pattern 1: Apply the Three Pillars
"Using a case study, explain how the three pillars of sustainability are interconnected."

Strategy: Choose a clear case study (e.g., fast fashion, palm oil, mining). Discuss environmental, social, AND economic impacts. Show interconnections.

💡 Pattern 2: Analyse SDG Interconnections
"Analyse how progress towards one SDG can support or hinder progress towards others."

Strategy: Choose 2–3 specific SDGs. Show positive spillovers AND potential trade-offs. Use data or examples.

💡 Pattern 3: Calculate & Interpret Ecological Footprint
"Using the data provided, calculate the ecological deficit/surplus for Country X and suggest one way to reduce it."

Strategy: Ecological Footprint − Biocapacity = Deficit (if negative) or Surplus (if positive). Always interpret the result and suggest a realistic solution.

💡 Pattern 4: Explain I=PAT
"Explain how changes in population, affluence, or technology can affect environmental impact, using the I=PAT equation."

Strategy: Define each variable. Give a numerical example showing how changing one variable changes I. Discuss that T can both increase and decrease impact.

💡 Pattern 5: Evaluate Sustainability Models
"Compare the three pillars model with the nested model. Which model better represents the relationship between the environment, society, and the economy? Justify your answer."

Strategy: Describe both models. Note that three pillars implies equality while nested shows dependency. Argue for one (usually nested is stronger environmentally) and justify with reasoning.

General Exam Advice

Always use specific examples — countries, organisations, data, or case studies
Address all three pillars — don't focus only on environmental aspects
Use key terminology correctly — ecological footprint, carrying capacity, HDI, I=PAT, etc.
For evaluation questions: always present both sides before making a judgement
For HL questions: go beyond description to critical analysis — discuss strengths AND limitations
Manage your time — don't spend too long on one question; allocate time based on marks