IB DP Environmental Systems and Societies – Natural resources, energy and solid waste Study Guide

This study guide teaches Topic 7 of IB Diploma Programme Environmental Systems and Societies (ESS): natural resources, energy and solid waste. It is aligned to the IB Environmental systems and societies subject brief, first assessment 2026, and covers syllabus sections 7.1–7.3. Topic 7 is studied at both SL (10 teaching hours) and HL (18 hours); HL students study some topics in extra depth. 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 public brief names Topic 7 and its hours but not the detailed understandings, so check your school’s copy of the subject guide for the full list.

Related pages: revision notes for this unit · practice questions for this unit · ESS course hub · printable ESS checklist · ESS syllabus guide · Topic 1 Foundations

What this unit covers

Syllabus section	What you must be able to do	SL/HL
7.1 Natural resources – uses and management	Classify resources; explain natural capital and natural income; calculate sustainable yield; explain why resource value changes; evaluate management strategies and the tragedy of the commons	SL and HL
7.2 Energy sources – uses and management	Compare renewable and non-renewable sources; explain the factors behind a society’s energy choices; evaluate energy security and energy efficiency strategies	SL and HL
7.3 Solid waste	Describe the types and sources of solid domestic waste (SDW); evaluate landfill, incineration, composting, recycling and reuse; apply the pollution management model and the waste hierarchy	SL and HL

Topic 7 applies two ideas from Topic 1 — natural capital and the pollution management model — to real resources, energy systems and waste streams.

7.1 Natural resources – uses and management

Natural capital and natural income

A natural resource is any part of the natural world that humans use. ESS treats these resources as natural capital — a stock — that can produce natural income — a flow of goods or services. A forest is natural capital; the timber that grows each year, the water it filters and the carbon it stores are natural income.

• Renewable natural capital can regenerate within a human timescale if harvested at or below its rate of growth. Examples: forests, fish stocks, groundwater that is recharged by rain.
• Non-renewable natural capital forms far more slowly than we use it, so any extraction reduces the stock. Examples: coal, oil, metal ores.

Natural income includes goods (timber, food, fibre) and services. Ecosystem services are often grouped as provisioning (food, fresh water), regulating (flood control, climate regulation, pollination), supporting (soil formation, nutrient cycling) and cultural (recreation, spiritual value).

Sustainable yield

The sustainable yield (SY) is the rate of increase of natural capital — the amount that can be harvested without reducing the stock. For a renewable resource:

SY = (total biomass or energy at time t + 1) − (total biomass or energy at time t)

If the harvest equals the SY, the stock stays the same. If it is larger, the stock is being run down. The maximum sustainable yield (MSY) is the largest harvest that can be taken year after year. With logistic growth, growth is fastest at about half the carrying capacity, so MSY is taken there. It is risky: stock estimates are uncertain and the margin against a bad year is small.

Worked example: forest sustainable yield

A 250 ha plantation holds 18,400 t of wood biomass on 1 January 2024. With no felling during 2024, it holds 19,320 t on 1 January 2025. The owner plans to fell 1,150 t each year.

Step 1  SY = 19,320 − 18,400 = 920 t per year
Step 2  As a percentage of the stock: 920 ÷ 18,400 × 100 = 5.0 % per year
Step 3  Planned harvest − SY = 1,150 − 920 = 230 t per year above SY
Step 4  Stock change = 920 − 1,150 = −230 t per year
Step 5  After 10 years (if growth stays at 920 t per year):
        18,400 − 10 × 230 = 16,100 t

Conclusion: the plan takes more than the natural income, so natural capital shrinks — probably faster than shown, as a smaller stock usually grows more slowly. Sustainable felling is at most 920 t per year.

Why resource value changes

The value of a resource is not fixed. It depends on technology, culture, economics and politics.

• Technology: uranium had little value before nuclear power; lithium became far more valuable once rechargeable batteries spread.
• Culture: a sacred forest may be valued for its spiritual worth rather than its timber.
• Economics: a rise in the market price can make a low-grade ore worth mining.

Use values (timber sold) are easier to price than non-use values (knowing a species exists). HL students meet valuation in the HL-only lens on environmental and ecological economics.

The tragedy of the commons

A common-pool resource — an ocean fishery, a shared pasture, an aquifer, the atmosphere — is open to many users. Each user gains the full benefit of taking a little more, but the cost of depletion is shared by everyone. So each user acts rationally, and the resource is overexploited. This is the tragedy of the commons.

It is not inevitable: communities with clear boundaries, agreed rules and penalties for cheating have managed commons sustainably.

Managing resources

Strategy	How it works	Limitation
Quotas and permits	Cap the total harvest or extraction	Needs reliable stock data and enforcement
Protected areas	Remove some capital from use so it can recover	Can displace local people; edge effects
Pricing and taxes	Make users pay closer to the true cost	Can hit poorer users hardest
Certification schemes	Consumers choose sustainably produced goods	Depends on honest auditing and consumer demand
Community management	Local users set and police rules	Works best in small, stable groups
Circular economy	Keep materials in use; design out waste	Needs redesign of products and supply chains

Resource security means reliable, affordable access to the resources a society needs. A country that depends on imports for water, food or minerals is less secure, because supply can be cut by conflict, trade disputes or climate shocks.

7.2 Energy sources – uses and management

Renewable and non-renewable energy

Source	Type	Key advantages	Key disadvantages
Coal, oil, natural gas	Non-renewable	Reliable, high energy density, existing infrastructure	CO₂ emissions, air pollution, finite
Nuclear (fission)	Non-renewable	Very low operational CO₂, reliable output	Radioactive waste, high build cost, accident risk
Hydroelectric	Renewable	Reliable, can be stored in reservoirs	Floods land, displaces people, traps sediment
Wind	Renewable	No fuel cost, low operational emissions	Intermittent, visual and noise impacts
Solar	Renewable	Works at many scales, falling costs	Intermittent, needs storage for night-time
Geothermal	Renewable	Steady output	Only practical in tectonically active areas
Tidal and wave	Renewable	Predictable (tidal)	Few suitable sites; affects estuary habitats
Biomass	Renewable	Can use waste; storable	Land competition; low-carbon only if regrowth replaces what is burned

Factors behind energy choices

A society’s energy mix reflects:

• availability of local resources (a country with rivers and mountains may favour hydro)
• technology and cost (capital cost, running cost, grid capacity)
• economic factors (existing industry and jobs, fuel prices)
• political factors (government policy, subsidies, international agreements on emissions)
• cultural and social attitudes (public opposition to nuclear power or to wind turbines nearby)
• environmental concerns (climate change, air quality)
• energy security (see below)

Energy security

Energy security is reliable, affordable access to enough energy. A country is less secure when it imports much of its fuel, relies on one or two sources, or depends on supply routes that pass through unstable regions. Strategies to improve it include diversifying sources, developing local renewables, storing fuel or electricity, and reducing demand through energy efficiency (the same output with less energy, such as LED lighting or insulated buildings) and energy conservation (using less, such as lowering heating settings).

Worked example: interpreting an energy mix

Electricity generated in a fictional country (TWh):

Source	2015	2025
Coal	140	110
Natural gas	60	80
Oil	10	5
Nuclear	20	20
Hydro	35	38
Wind	10	32
Solar	2	20
Biomass	3	5
Total	280	310

Renewable 2015 = 35 + 10 + 2 + 3 = 50 TWh → 50 ÷ 280 × 100 = 17.9 %
Renewable 2025 = 38 + 32 + 20 + 5 = 95 TWh → 95 ÷ 310 × 100 = 30.6 %
Fossil 2015 = 210 TWh → 75.0 %;  Fossil 2025 = 195 TWh → 62.9 %
Wind + solar: 12 → 52 TWh, an increase of 40 ÷ 12 × 100 = 333 %
Total generation rose by 30 ÷ 280 × 100 = 10.7 %

Interpretation: the renewable share rose by about 13 percentage points, but fossil generation fell by only 15 TWh because demand grew. The switch from coal to gas lowers CO₂ per unit but may raise dependence on imported gas — state this tension.

7.3 Solid waste

Types and sources

Solid domestic waste (SDW) is household rubbish: food and garden waste, paper and card, plastics, glass, metals, textiles and electronic waste (e-waste). Waste per person tends to rise with income and urbanisation. E-waste contains toxic metals but also valuable ones, so it is both a pollutant and a resource.

Strategies for managing SDW

The pollution management model from Topic 1 gives three levels:

1. Altering human activity (prevention) — reduce packaging, buy durable goods, repair, reuse.
2. Controlling the release of the pollutant — recycling, composting, incineration with energy recovery, deposit-return schemes, taxes on landfill.
3. Clean-up and restoration — collecting litter, reclaiming old landfill sites, beach clean-ups.

Strategies higher up the waste hierarchy (reduce → reuse → recycle/compost → recover energy → dispose) tackle causes rather than outcomes.

Method	Advantages	Disadvantages
Landfill	Cheap, handles mixed waste	Uses land; methane and leachate; wastes materials
Incineration	Greatly reduces volume; can generate electricity	Air emissions, toxic ash, high cost; can discourage recycling
Composting	Turns organic waste into soil improver; cuts landfill methane	Needs separate collection; contamination
Recycling	Saves raw materials and often energy	Needs sorting and markets; some materials degrade each cycle
Reuse	Keeps products in use with little processing	Needs changes in habits and product design

Worked example: landfill lifespan

A town of 80,000 people produces 30,400 t of SDW a year. 25% is recycled or composted; the rest is landfilled. Compacted waste has a density of 0.75 t/m³. The landfill has 380,000 m³ of space left.

Waste per person = 30,400,000 kg ÷ 80,000 = 380 kg per year (1.04 kg per day)
Landfilled mass  = 0.75 × 30,400 = 22,800 t per year
Landfilled volume = 22,800 ÷ 0.75 = 30,400 m³ per year
Lifespan = 380,000 ÷ 30,400 = 12.5 years

If a food-waste collection and better recycling cut landfilled mass to 15,000 t a year:

Volume = 15,000 ÷ 0.75 = 20,000 m³ per year
Lifespan = 380,000 ÷ 20,000 = 19 years
Diversion from landfill = (30,400 − 15,000) ÷ 30,400 × 100 = 50.7 %

If organic waste is the largest fraction, composting is the obvious first target; it also cuts landfill methane.

Common errors

• Calling natural income “the resource”. The stock is capital; the yearly flow is income.
• Calculating sustainable yield as a harvest total. SY is the growth of the stock, not what is removed.
• Saying renewable energy has “no environmental impact”. Name the impact: land use, habitat change, materials.
• Calling nuclear power renewable. Uranium is a finite ore.
• Treating energy security as the same thing as renewable energy. A country can be secure on domestic coal and insecure on imported solar panels.
• Describing recycling as the best waste strategy. On the waste hierarchy, reduction and reuse come first.
• Forgetting units (t per year, TWh, m³) in data answers.

Where to go next

Condense this unit with the revision notes, then test yourself with the practice questions (both linked at the top). For exam structure, see ESS exam preparation and the ESS assessment revision notes. Energy flow in ecosystems is covered in Topic 2 Ecology.

Official syllabus

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

The brief gives Topic 7 Natural resources 10 teaching hours at SL and 18 at HL. It does not list the subtopics or learning outcomes for this topic, so the numbered subtopics and outcomes on this page follow the syllabus numbering used in the printable ESS checklist, not the brief itself.