Environment and population relationships; food, health and disease; the demographic transition and population change; the natural-resource and carrying-capacity debate; and the principles of population ecology applied to people.

What this dot point is asking

AQA section 3.2.4 wants you to explain the relationships between population and the environment, analyse food, health and disease, apply the Demographic Transition Model to population change, and evaluate the debate over carrying capacity, natural resources and the principles of population ecology applied to people. The synoptic thread is whether the planet can sustainably support a growing population, the central question that links physical limits to human innovation.

Environment and population relationships

The physical environment, climate, soils, water and disease vectors, strongly influences population distribution, density and the type of agriculture possible. Zonal soils and climate set limits on food production, so fertile, well-watered regions support dense populations while arid and infertile zones support few people. People in turn modify the environment through farming, irrigation, deforestation and pollution, so the relationship is two-way and dynamic.

Food, health and disease

The global pattern of disease links climate, environment and development. Malaria, for example, is concentrated in warm, humid tropical regions where the Anopheles mosquito vector thrives, and its burden falls heaviest on lower-income countries, reducing economic productivity and reinforcing poverty. Improvements in nutrition, sanitation, vaccination and health care drive the long-term fall in mortality.

The demographic transition and population change

Population change is driven by fertility, mortality and migration. Population structure, shown in age-sex pyramids, reveals dependency ratios and shapes policy: a youthful pyramid (wide base) implies high future growth and pressure on schools, while an ageing pyramid (top-heavy) implies a rising elderly dependency ratio and pressure on pensions and health care.

The carrying capacity debate

The central debate sets Malthusian and neo-Malthusian pessimists (resources cap population, so unchecked growth leads to crisis) against Boserupian and technological optimists (population pressure stimulates the innovation that raises output to match demand). The concepts of the ecological footprint and the planet's biocapacity help assess whether current consumption is sustainable. Crucially, rich countries have by far the largest per-capita footprints, so the debate is as much about consumption as about raw numbers.

Try this

Q1. Define carrying capacity. [2 marks]

• Cue. The maximum population an environment can support sustainably given available resources and technology.

Q2. State the main difference between the Malthusian and Boserupian views. [2 marks]

• Cue. Malthus says resources limit population; Boserup says population pressure drives innovation that raises output.

Q3. Explain how a country's position on the DTM affects its population structure. [4 marks]

• Cue. Stage 2 to 3 gives a wide-based youthful pyramid (high growth, high youth dependency); stage 4 to 5 gives a top-heavy ageing pyramid (slow or negative growth, high elderly dependency).