IB Diploma Environmental Systems & Societies SL · Human Systems and Resource Use
Mini-Lesson
Human Systems and Resource Use
This mini-lesson examines humanity as an environmental force: population dynamics (birth and death rates, natural increase, doubling time and the demographic transition), the drivers that raise or lower population growth, our resource use and ecological footprint, solid domestic waste and the waste hierarchy, the shift from a linear to a circular economy, and how human development links to environmental impact.
Sustainability lens: total impact depends on population size, consumption per person and the technology used. Reducing waste and closing material loops is central to living within planetary limits.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you're ready.
Human systems · population
Population dynamics
Key demographic rates describe how populations change:
Crude birth rate (CBR) — births per 1000 people per year.
Crude death rate (CDR) — deaths per 1000 people per year.
Natural increase rate (NIR) — (CBR − CDR), usually expressed as a percentage per year.
Total fertility rate (TFR) — average children per woman; ~2.1 gives a stable population (replacement level).
Calculate
Your turn — natural increase rate
1A country has a crude birth rate of 32 per 1000 and a crude death rate of 12 per 1000 per year. Calculate the natural increase rate as a percentage per year.
2A population grows at 2% per year. Using the rule of 70 (doubling time ≈ 70 ÷ growth rate), calculate how many years it takes the population to double.
years
Hint: doubling time = 70 ÷ 2.
Human systems · transition
The demographic transition model
The demographic transition model (DTM) describes how birth and death rates change as a country develops:
Stage 4 — low CBR and CDR; stable, large population.
Stage 5 — CBR below CDR; population ages and may shrink.
Age–sex pyramids show this: a wide base means rapid growth (Stage 2); a column or top-heavy shape means an ageing, stable or shrinking population (Stage 4–5).
Quick check
Reading the model
?A country has a rapidly falling death rate but a still-high birth rate, giving very fast population growth. Which stage of the demographic transition model is this?
Human systems · drivers
What changes population growth
Birth rates fall — and growth slows — as countries develop, driven by:
Education, especially of girls and women — the single strongest factor lowering fertility.
Access to healthcare and contraception, and family planning.
Falling child mortality, so families choose fewer children.
Urbanisation and rising incomes, where children cost more and work less.
Cultural, religious and political factors (and some pro- or anti-natalist policies) also shape fertility, so trajectories differ between countries.
Quick check
Lowering the birth rate
?Which factor is most strongly associated with falling birth rates as a country develops?
Resource use · footprints
Resource use and the ecological footprint
The ecological footprint measures the land and water area needed to supply a population’s resources and absorb its wastes, in global hectares (gha). It rises with consumption and with carbon-heavy lifestyles.
If a population’s footprint exceeds the biocapacity available, it runs an ecological deficit — living beyond the planet’s means. Wealthy nations typically have footprints several times larger than low-income nations.
Calculate
Your turn — a nation’s footprint
3A country of 4 million people has an average ecological footprint of 3.5 global hectares per person. Calculate the country’s total ecological footprint.
million gha
Hint: total = footprint per person × population = 3.5 × 4.
Resource use · waste
Solid domestic waste and the waste hierarchy
Solid domestic waste (SDW) — household rubbish (food, paper, plastics, glass, metals) — is rising as consumption grows. Disposal options differ in impact:
Landfill — cheap but takes land, leaks leachate and emits methane.
Incineration — cuts volume and can recover energy, but emits pollutants.
Recycling and composting — recover materials and nutrients, saving resources.
Waste hierarchy (best first): Reduce → Reuse → Recycle → Recover → Dispose. Preventing waste beats dealing with it.
Sort it
Sort the waste actions
Tap an action, then tap where it sits in the waste hierarchy.
🚫 Reduce
🔁 Reuse
♻️ Recycle
Calculate
Your turn — recycling rate
4A city produces 500 000 tonnes of solid domestic waste a year and recycles 150 000 tonnes of it. Calculate the percentage recycled.
%
Hint: (150 000 ÷ 500 000) × 100.
Quick check
Top of the hierarchy
?According to the waste hierarchy, which option should be the first priority for managing waste?
Resource use · circular economy
From a linear to a circular economy
The traditional linear economy is "take → make → use → dispose" — it depletes resources and creates waste.
A circular economy designs waste out: products are made to be repaired, reused, remanufactured and recycled, so materials cycle back into production (a "cradle-to-cradle" approach). This cuts resource extraction, waste and emissions while keeping economic value.
Quick check
Closing the loop
?Which of these best describes a circular economy?
Human development · HDI
Development and environmental impact
The Human Development Index (HDI) combines income (GNI per capita), education and life expectancy into a single 0–1 measure of development.
Development brings clear benefits, but higher incomes usually mean higher consumption and a larger ecological footprint. A central sustainability challenge is decoupling improvements in human wellbeing from rising environmental impact.
Quick check
Development and footprint
?As countries move up the Human Development Index, what typically happens to their ecological footprint per person?
Match it
Match the human-systems terms
Tap a statement on the left, then its matching answer on the right.
Statement
Answer
Recap
The big ideas to know
Population: CBR, CDR, NIR and doubling time (70 ÷ growth rate); TFR ~2.1 is replacement
Transition: the DTM runs Stage 1 (high, high) to Stage 5 (below replacement); education lowers fertility
Footprint: ecological footprint in gha rises with consumption; deficit = footprint > biocapacity