Where people live: physical setting and global patterns
Distribution means how people are spread out. Density = people ÷ area (people per km²). People crowd on fertile lowlands, river valleys and coasts with reliable water and a mild climate. Very cold, very dry, very high or very wet and forested lands hold few people.
World population passed 8 billion in 2022. More than half live in Asia. Dense clusters include the Ganga plain, eastern China, Java, the Nile valley and north-west Europe. Growth is now fastest in sub-Saharan Africa, while many countries in Europe and East Asia are shrinking.
Environment and food
Food production is not spread evenly: some regions export, others import or go hungry. Consumption rises with income, especially of meat and dairy.
Farming systems
A farm is a system: inputs (land, water, seeds, labour, fertiliser) → processes (ploughing, harvesting) → outputs (crops, animals). Systems can be intensive or extensive, subsistence or commercial, arable, pastoral or mixed. Productivity is output per hectare or per worker.
Climate and soils
Climate type (tropical wet, arid, temperate, cold) limits what can be grown. Zonal soils follow climate belts: e.g. leached tropical soils (latosols), fertile grassland soils (chernozems) and acidic podzols under coniferous forest. Soil problems include erosion, waterlogging, salinisation and structural damage; they are managed with terracing, contour ploughing, drainage and better irrigation.
Food security
Food security means everyone always has enough safe, nutritious food. Strategies: higher yields (new seeds, irrigation, GM crops), land reform, fairer trade, reducing waste, storage, and helping smallholders. India's Public Distribution System and the Green Revolution are examples.
Environment, health and well-being
Health is measured by life expectancy, infant mortality and disease rates. The epidemiological transition: as countries develop, deaths from infectious disease fall and non-communicable diseases (NCDs) take over.
Environment and disease
Climate, water and housing shape disease. Dirty water spreads cholera; smoky air from traffic and indoor stoves causes lung disease.
Malaria (vector-borne)
A parasite carried by female Anopheles mosquitoes. It needs warm temperatures and still water for breeding, so it is common in the tropics. Control: bed nets, spraying, draining water, medicines, and now vaccines.
A non-communicable disease
Heart disease is linked to diet, smoking, low exercise, age and air pollution. It is rising fast in cities in South Asia.
Agencies
The WHO, governments and NGOs fund vaccines, nets, clean water and health education.
Population change
Vital rates: crude birth rate and death rate per 1000 people per year. Natural increase (%) = (birth rate − death rate) ÷ 10. Total fertility rate = average children per woman (2.1 = replacement level).
Demographic transition model (DTM)
Stage 1 high and fluctuating rates; Stage 2 death rate falls (food, water, medicine) → rapid growth; Stage 3 birth rate falls (cities, education of girls, contraception); Stage 4 both low; Stage 5 births below deaths → decline. It is a model based on Europe and may not fit every country.
Age-sex structure and the dividend
A pyramid shows males and females in age groups. A wide base means a young population; a column or inverted shape means ageing. When fertility falls, the working-age share grows: the demographic dividend. Dependency ratio = (0–14 + 65+) ÷ (15–64) × 100.
Refugees and migrants
Migrants move by choice (work, study, family); refugees are forced out by conflict or persecution. Causes are push and pull factors; effects include remittances, labour supply, brain drain and pressure on services.
Population ecology applied to people
Overpopulation: too many people for the resources and technology. Underpopulation: too few to use resources fully. Optimum population: the size that gives the highest living standard.
Carrying capacity: the largest population an area can support sustainably. The ecological footprint measures the land and water needed to supply a person's use and absorb their waste (global hectares).
The population–resources–pollution model links them: more people use more resources and create more pollution, which can damage resources.
The debate
- Malthus (1798): population grows geometrically, food arithmetically → famine, disease and war act as checks.
- Neo-Malthusians (e.g. Limits to Growth, 1972): finite resources and pollution will limit growth.
- Boserup (1965): population pressure drives farming innovation.
- Simon: people are the 'ultimate resource'; prices and ideas solve shortages.
Global population futures and case studies
Ozone loss lets more UV-B reach the ground, raising skin cancer and cataract risk; the Montreal Protocol (1987) is helping the ozone layer recover. Climate change can spread malaria and dengue to new areas, cause heat stress and harm food supply.
UN projections suggest world population may peak at around 10 billion in the 2080s, with growth mostly in Africa and decline in Europe and East Asia.
Case studies to prepare
One country with growth or decline (for example Nigeria growing, or Japan shrinking): its rates, structure, policies and environmental links. One local area: how place, income and environment affect health.
Try it
In the 3D simulator set birth rate 35 and death rate 10, then 10 and 12. Note the doubling time each time. At home, list the ages of everyone on your street or in your family and sketch your own mini pyramid.
Key formulas and definitions
- Population density = population ÷ area (people per km²)
- Natural increase (%) = (crude birth rate − crude death rate) ÷ 10
- Doubling time ≈ 70 ÷ growth rate (%)
- Dependency ratio = (aged 0–14 + aged 65+) ÷ (aged 15–64) × 100
- Replacement-level fertility ≈ 2.1 children per woman
- Population change = births − deaths + immigration − emigration
Worked examples
1. A country has a birth rate of 32 per 1000 and a death rate of 8 per 1000. Find the natural increase and doubling time.
(32 − 8) ÷ 10 = 2.4% per year. Doubling time ≈ 70 ÷ 2.4 ≈ 29 years.
2. A population has 30 million aged 0–14, 60 million aged 15–64 and 10 million aged 65+. Find the dependency ratio.
(30 + 10) ÷ 60 × 100 ≈ 67. For every 100 workers there are about 67 dependants.
3. Which DTM stage fits birth rate 38, death rate 15 and why?
Stage 2: the death rate has fallen thanks to better health and food, but the birth rate is still high, so growth is rapid.
4. Use the population–resources–pollution model to explain a city's air problem.
More people → more vehicles and power demand (resources) → more exhaust (pollution) → more lung disease and lower quality of life, which then needs more resources to fix.
5. Contrast Malthus and Boserup using the Green Revolution.
Malthus predicts food runs out as numbers grow. In India in the 1960s new seeds, fertiliser and irrigation raised yields fast — closer to Boserup's idea that pressure brings innovation. But soil damage and falling water tables show limits, which neo-Malthusians stress.
Common mistakes
- Saying the death rate falls because people have fewer children. Deaths fall first because of food, water and medicine.
- Treating the DTM as a law that every country must follow on the same timetable.
- Mixing up overpopulation (people vs resources) with high density. A dense rich city can be well supplied.
- Saying malaria is spread by dirty water. It is spread by mosquitoes; still water is where they breed.