Why "global change"?

The core takes a global, systems view: people, climate and resources are all changing together, and the power to cause and to cope with change is unevenly spread.

• Population: how many people, where, and how the age structure is 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 loves "examine", "evaluate" and "to what extent" — reward comes from data skills plus a balanced, located argument.

Population distribution & density

People are spread very unevenly. Density = people ÷ area. Distribution is shaped by:

• Physical factors — relief, climate, water, soils (fertile river valleys and deltas are densely settled; deserts and high mountains are sparse).
• Human factors — jobs, cities, transport, history and government policy.

Scale: distribution looks different at global, national and local scales — a "sparse" country can contain a very dense capital city.

Where do people cluster?

Births, deaths & natural increase

A population changes through births, deaths and migration. The natural increase rate (from births and deaths only) is:

Because a steady percentage growth compounds, we estimate doubling time with the rule of 70:

Your turn — natural increase

Your turn — doubling time

Age structure & dependency

The Demographic Transition Model (DTM) shows how birth and death rates fall as a country develops, changing its age structure. A key measure is the dependency ratio:

Two challenges: a youthful structure (many under 15) strains schools and jobs; an ageing structure (many 65+) strains pensions and healthcare. Both raise the dependency ratio.

Your turn — dependency ratio

Migration & population policy

Migration redistributes people. It is driven by push factors (poverty, conflict, hazards) and pull factors (jobs, safety, services). Governments try to steer change with policy:

• Anti-natalist — reduce birth rates (e.g. family-planning programmes).
• Pro-natalist — raise birth rates in ageing societies (incentives for larger families).
• Migration policy — points systems, work visas, integration or restriction.

Possibilities & power: the "gender and change" strand stresses that empowering women (education, work) is one of the strongest drivers of falling fertility.

Which core unit?

Tap a term, then tap the Global Change unit it belongs to.

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 to these impacts, and how little it can cope. It depends on physical exposure and on wealth, governance and infrastructure.

Key idea: the places that have emitted the least are often the most vulnerable — a core question of climate justice and power.

Same hazard, different outcome

Adaptation vs mitigation

Resilience is the capacity to absorb and recover from change. There are two response strategies — the exam wants you to tell them apart:

• Mitigation — tackling the cause: cutting greenhouse-gas emissions (renewables, carbon pricing, reforestation).
• Adaptation — living with the consequences: sea walls, drought-resistant crops, early-warning systems.

Possibilities: most realistic futures combine both — mitigation slows the change, adaptation manages what can no longer be avoided.

Adapt or mitigate?

Global resource consumption

As populations grow and become wealthier, per-capita demand for water, food and energy rises. We track this with index numbers, which rescale data so a base year = 100:

The ecological footprint compares demand on nature with the Earth's biocapacity: living beyond biocapacity is an "ecological overshoot".

Your turn — index number

Match the term to its meaning

Tap a description on the left, then its matching term on the right.

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 a shortage in one cascades into the others (e.g. energy is needed to pump water; water is needed to grow food).

Sustainability & power: the concept of "circular economy" and the debate between neo-Malthusian pessimism and technological optimism (Boserup) are exactly the kinds of ideas an "evaluate" question rewards.

Reading the nexus

The big ideas to know

You've covered the key ideas across the three units of the Global Change core. Press Finish to see your score.