Population and Migration: KS3 Geography Explained

Population geography asks why people live where they do, why populations grow or shrink, and what happens when people move. These are some of the most significant questions in human geography — directly linked to resource use, climate change, urbanisation, and political decision-making at every scale from village to global.

How the world's population has changed

The global population reached 8 billion people in November 2022. For most of human history, population growth was slow: it took until 1804 to reach 1 billion, then 123 years to add the second billion (1927). But the pace accelerated dramatically: the third billion was added in just 32 years (1959), the fourth in 14 years (1974), and by the 1980s the world was adding around 80 million people per year.

Why the acceleration? The key driver was a dramatic fall in death rates — particularly infant mortality — driven by improvements in medicine, sanitation, food production, and public health, without a corresponding immediate fall in birth rates.

Key population terms

Understanding population geography requires precise use of the following terms:

Term | Definition
Birth rate | Number of live births per 1,000 people per year
Death rate | Number of deaths per 1,000 people per year
Natural increase | Birth rate minus death rate (when positive, population grows)
Life expectancy | Average number of years a person born today is expected to live
Infant mortality rate | Number of deaths per 1,000 live births before the age of one
Fertility rate | Average number of children born to each woman during her lifetime
Population density | Number of people per square kilometre

The Demographic Transition Model (DTM)

The Demographic Transition Model (DTM) is the most important conceptual framework for understanding population change at KS3. It describes how the relationship between birth rate and death rate changes as a country develops economically and socially, using four (or five) stages.

Stage 1: High Fluctuating

Both birth rates and death rates are high. Population is small and grows very slowly. Examples: pre-industrial societies; remote tribal communities today.

High birth rates because: no family planning; children needed for agricultural labour; high infant mortality means parents have many children hoping some survive.

High death rates because: disease, famine, poor sanitation, war.

Stage 2: Early Expanding

Birth rates remain high, but death rates fall sharply. Population grows rapidly. Examples: Sub-Saharan Africa; parts of South Asia in the early-to-mid 20th century.

Death rates fall because: improved medicine (vaccines), better food supply, improved sanitation.

Birth rates remain high because cultural and social attitudes change slowly.

Stage 3: Late Expanding

Birth rates begin to fall; death rates continue to fall slowly. Population still grows but at a slower rate. Examples: Brazil, India (current).

Birth rates fall because: access to contraception; women's education and employment; urbanisation makes large families less economically necessary.

Stage 4: Low Fluctuating

Both birth rates and death rates are low. Population is large but stable or growing very slowly. Examples: UK, France, United States.

Stage 5: Decline (added later)

Birth rates fall below death rates. Population begins to shrink. Examples: Japan, parts of Eastern Europe.

Stage | Birth rate | Death rate | Population change
1 | High | High | Stable/slow growth
2 | High | Falling | Rapid growth
3 | Falling | Low | Slower growth
4 | Low | Low | Stable
5 | Very low | Low | Decline

Population distribution and density

Population is not spread evenly across the Earth. Some areas are very densely populated (many people per km²) and others are almost empty. The factors that explain this pattern include:

Physical factors:

Climate: most people live in temperate climates with reliable rainfall. Very cold, very hot, or very dry regions are sparsely populated.

Terrain: flat, low-lying land is easier to farm, build on, and transport goods across. Mountain ranges, deserts, and dense rainforest are barriers to settlement.

Water: populations cluster near rivers, lakes, and coastlines, which provide fresh water, food, and transport routes.

Human factors:

History of settlement: some regions have been densely populated for thousands of years, developing infrastructure, trade networks, and political stability that attract more people.

Economic opportunity: areas with industry, employment, and services attract migrants; regions with declining economies lose population.

What is migration?

Migration is the movement of people from one place to another, with the intention of settling in the new location. Geographers classify migration in several ways:

Internal migration: movement within a country (e.g. from a rural area to a city — rural-to-urban migration)

International migration: movement between countries

Voluntary migration: the migrant chooses to move (economic opportunity, family reunification)

Forced migration: the migrant has no real choice (war, persecution, natural disaster, famine)

Push and pull factors

Migration is usually explained using the push-pull model, which classifies the reasons for movement as either:

Push factors: negative conditions at the origin that encourage people to leave

Pull factors: positive conditions at the destination that attract people

Push factors | Pull factors
War and political persecution | Safety and political stability
Poverty and unemployment | Economic opportunity and higher wages
Natural disaster or drought | Reliable food supply and climate
Poor healthcare and education | Good healthcare, schools, and infrastructure
Environmental degradation | Environmental quality

In reality, migration decisions involve both push and pull factors acting together, often alongside intervening obstacles (the barriers that make migration difficult, such as distance, cost, legal restrictions, and cultural differences).

A worked example: Syrian migration to Europe (2015–2016)

During the Syrian Civil War, which began in 2011, millions of Syrians were displaced. The peak year for arrivals in Europe was 2015, when over one million people crossed into EU countries. This case illustrates push-pull dynamics clearly:

Push factors from Syria:

Armed conflict and civilian casualties

Destruction of homes, hospitals, and schools

Collapse of economic activity and employment

Pull factors to Europe (particularly Germany, Sweden, UK):

Existing Syrian diaspora communities (family reunification)

Relatively high wages and employment opportunities

Functioning welfare systems and refugee legal frameworks

Geographic accessibility via Turkey, Greece, and the Balkans

Intervening obstacles:

Dangerous sea crossing from Turkey to Greece

Long overland journeys through multiple countries

Legal and policy barriers (Dublin Regulation requiring asylum claims in first EU country of entry)

This case illustrates that migration is rarely simple: it involves desperate decisions made by people weighing genuine dangers at home against real uncertainties about the journey and the destination.

The impacts of migration

Migration has both positive and negative impacts — for the destination country, the origin country, and for the migrants themselves.

For the destination country:

Economic benefits: migrants often fill labour shortages, pay taxes, and contribute to economic growth

Cultural enrichment: cultural diversity and new skills

Potential pressures on housing, healthcare, and public services if migration is rapid and large-scale

For the origin country:

Remittances: migrants send money home, which supports families and local economies (global remittances exceeded $700 billion in 2020, according to the World Bank)

Brain drain: highly skilled workers leave, reducing human capital in the origin country

Reduced unemployment and population pressure

Frequently asked questions

What is the demographic transition model in geography?

The Demographic Transition Model (DTM) is a model that describes how a country's population changes as it develops economically. It has four or five stages. In Stage 1, both birth rates and death rates are high. In Stage 2, death rates fall sharply while birth rates remain high, producing rapid population growth. In Stage 3, birth rates begin to fall. In Stage 4, both rates are low and population stabilises. A proposed Stage 5 describes populations where birth rates fall below death rates and the population begins to decline.

What are push and pull factors in migration?

Push factors are the negative conditions in a migrant's home area that encourage them to leave — for example, war, poverty, unemployment, or natural disaster. Pull factors are the positive conditions in the destination that attract migrants — for example, job opportunities, safety, better healthcare, or family connections. Most migration is driven by a combination of both, along with the intervening obstacles (cost, distance, legal barriers) that make migration difficult to achieve even when people want to move.

What is the difference between a refugee and an economic migrant?

A refugee is a person who has fled their home country because they face serious risk of persecution, war, or violence, and who cannot return safely. Under international law, refugees are entitled to protection in countries that have signed the 1951 Refugee Convention. An economic migrant moves primarily to improve their economic circumstances — for better wages, employment, or living standards. In practice, the distinction can be complex: many displaced people face both conflict and poverty, and the legal categories do not always capture the full reality of people's situations.

Why is the world's population growing unevenly?

Population growth is uneven because countries are at different stages of the Demographic Transition Model. Countries in Sub-Saharan Africa are largely in Stage 2 or early Stage 3, with high birth rates and rapidly falling death rates, producing rapid natural increase. Countries in Western Europe, Japan, and parts of East Asia are in Stage 4 or Stage 5, with low birth rates and ageing populations, producing very slow growth or decline. The gap in growth rates produces very different challenges: rapid urbanisation and youth unemployment in high-growth regions; an ageing workforce and pension pressures in low-growth ones.

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