The Geographic Perspectives — Global Change core is compulsory for every IB Geography student (Paper 2). Its three units — changing population, global climate, and global resource consumption & security — reward strong data skills and a synthesised argument.
Expect real calculations — natural increase, doubling time, dependency ratio and index numbers — alongside the concepts of vulnerability, resilience and security. Press Start.
Perspectives · framing
Why "global change"?
The core takes a global, systems view: people, climate and resources change together, and the power to cause and to cope with change is unevenly spread across places.
Population: how many people, where, and how age structures are shifting.
Climate: the causes of change and the very different vulnerability and resilience of places.
Resources: rising per-capita demand for water, food and energy, and the security of supply.
Command focus: Paper 2 rewards data skills plus a balanced, located, evaluative argument.
Population · distribution
Distribution, density & megacities
People are spread very unevenly. Density = people ÷ area. Increasingly, population concentrates in megacities (over 10 million) through urbanisation. Distribution is shaped by:
Physical factors — relief, climate, water and soils.
Human factors — jobs, cities, transport, history and policy.
Scale: a country that looks "sparse" nationally can still contain an extremely dense megacity — always specify the scale you mean.
Quick check
Where do people cluster?
?Which combination of physical conditions most encourages a dense population?
Population · change
Births, deaths & natural increase
A population changes through births, deaths and migration. The natural increase rate (from births and deaths only) is:
NIR (%/yr) = (CBR − CDR) ÷ 10CBR and CDR are per 1000 people; dividing by 10 converts "per 1000" into a percentage
Because steady percentage growth compounds, we estimate doubling time with the rule of 70:
doubling time ≈ 70 ÷ NIR (% per year)a quick approximation — small growth rates mean very long doubling times
Calculate
Your turn — natural increase
1A slow-growing country has a crude birth rate of 12 and a crude death rate of 9 (per 1000). Calculate the natural increase rate as a percentage per year.
%
Hint: NIR = (12 − 9) ÷ 10.
Calculate
Your turn — doubling time
2With that natural increase rate of 0.3% per year, estimate the doubling time using the rule of 70 (to the nearest year).
years
Hint: doubling time ≈ 70 ÷ 0.3 ≈ 233.
Population · structure
Ageing structures & dependency
The Demographic Transition Model shows birth and death rates falling as a country develops. Many high-income countries now face an ageing structure. A key measure is the dependency ratio:
dependency ratio = (young + old) ÷ working-age × 100young = under 15 · old = 65+ · working-age = 15–64
Ageing challenge: a large 65+ share raises the dependency ratio and strains pensions and healthcare — pro-natalist policy and later retirement are common responses.
Calculate
Your turn — dependency ratio
3In an ageing population, 18% are under 15, 27% are 65 or over, and 55% are of working age (15–64). Calculate the dependency ratio to 1 decimal place.
per 100
Hint: (18 + 27) ÷ 55 × 100 = 45 ÷ 55 × 100.
Population · migration & policy
Migration & population policy
Migration redistributes people, driven by push factors (poverty, conflict, hazards) and pull factors (jobs, safety, services). Governments steer change with policy:
Pro-natalist — raise birth rates in ageing societies.
Migration policy — points systems, work visas, integration or restriction.
Possibilities & power: the "gender and change" strand stresses that empowering women — through education and work — is one of the strongest drivers of falling fertility.
Sort it
Which core unit?
Tap a term, then tap the Global Change unit it belongs to.
📈 Population
🌡️ Global climate
⛏️ Resources
Climate · vulnerability
Global climate — causes & vulnerability
The enhanced greenhouse effect from rising CO₂, methane and other gases is warming the planet, shifting rainfall, raising sea level and intensifying some extremes.
Vulnerability is how exposed and sensitive a place is, and how little it can cope. It depends on physical exposure and on wealth, governance and infrastructure.
Climate justice: the places that have emitted the least are often the most vulnerable — a core question of power.
Quick check
Same hazard, different outcome
?Two low-lying coastal countries face the same rate of sea-level rise, yet one suffers far greater losses. Which idea best explains this?
Climate · resilience
Adaptation vs mitigation
Resilience is the capacity to absorb and recover from change. Two response strategies — know the difference:
Adaptation — living with the consequences: sea walls, drought-resistant crops, early-warning systems.
Possibilities: realistic futures combine both — mitigation slows the change, adaptation manages what can no longer be avoided.
Quick check
Adapt or mitigate?
?A country rapidly expands wind and solar power to cut its carbon emissions. This is best described as:
Resources · consumption
Global resource consumption
As populations grow and become wealthier, per-capita demand for water, food and energy rises. We track change with index numbers, which rescale data so a base year = 100:
index = (value ÷ base-year value) × 100an index of 150 means consumption is 50% higher than in the base year
The ecological footprint compares demand on nature with the Earth's biocapacity; living beyond biocapacity is an "ecological overshoot".
Calculate
Your turn — index number
4In the base year a country used 300 units of energy per person; this year it used 450 units. Calculate this year's consumption index (base year = 100).
index
Hint: index = (450 ÷ 300) × 100.
Match it
Match the term to its meaning
Tap a description on the left, then its matching term on the right.
Description
Term
Resources · security & sustainability
Resource security & the nexus
Resource security means reliable, affordable access to enough water, food and energy. These three are linked — the water–food–energy nexus — so stress in one cascades into the others. Water stress, for example, is measured as the share of available water withdrawn:
water stress = withdrawal ÷ available supply × 100higher percentages mean a country is drawing down more of its renewable water
Power & possibilities: the "circular economy" and the neo-Malthusian vs Boserup (technological optimism) debate are exactly what an "evaluate" question rewards.