The word “population” comes from the Latin term populus, which simply means “people.” In general, population refers to all the individuals of the same species living in the same geographical area. It can also mean the total number of people, plants, animals, or objects in a particular place or group.
Demography is the scientific study of human populations. It examines population growth, density, distribution, movement, and how these factors connect with economic and social development.
Human population refers to the total number of people living in a specific area at a given time. This area can be as small as a household or village, or as large as a region, country, continent, or the entire world.
Characteristics of Human Population
To understand a population better, we look at several key features:
Population Size This is the actual number of people in a given area at a specific time. For example, Tanzania’s population size according to the 2012 census was 44,928,923 people.
Population Density This measures how many people live per unit of area, usually per square kilometre. In 2012, Tanzania had a population density of about 48 people per square kilometre (based on its total area of 945,087 km², including inland water bodies).
Population Composition This refers to how the population is broken down by characteristics such as age, sex, marital status, occupation, education, religion, or socio-economic status. It helps us understand the overall structure of a population.
1. Population Composition by Age
People are grouped into different age categories. Typically:
- Individuals aged 15–64 are considered economically active (working-age population).
- Those below 15 and above 65 are economically dependent.
The dependency ratio shows the number of dependent people (young and elderly) relative to the working-age population. Studying age composition helps governments plan for schools, healthcare, and social services.
2. Population Composition by Sex
This looks at the number of males versus females in the population. It is often expressed as the sex ratio — the number of males per 100 females.
- Sex ratio > 100 → More males than females
- Sex ratio < 100 → More females than males
- Sex ratio = 100 → Equal number of males and females
Sex ratios can be influenced by differences in death rates, migration patterns, and the natural sex ratio at birth. Urban areas with many industries, for instance, often have higher male ratios due to job-seeking migration.
Population Structure
Population structure shows how males and females are distributed across different age groups. It is commonly presented using population pyramids — graphs that give a clear visual picture of a population’s age and sex distribution.
Population pyramids help us understand:
- Birth and death rates
- Life expectancy
- The number of dependants (young and elderly) compared to the working population
For example, less economically developed countries often have broad-based pyramids (many young people), while more developed countries tend to have narrower bases and larger elderly groups.
General Characteristics of Population
- Uneven distribution: People are not spread evenly across the land. Some areas are heavily populated while others have very few or no people.
- Dynamic nature: Populations are constantly changing due to births, deaths, and migration.
- Age-sex structure: Populations differ in proportions of males/females, age groups, and occupations.
- Variation in development: Some areas are highly developed, others developing or underdeveloped, largely due to differences in technology and resources.
- Populations also face various challenges such as diseases (e.g., HIV/AIDS), natural disasters, and environmental problems.
The Importance of Studying Population
Understanding population is crucial, especially in developing countries where rapid population growth is common. The study of population (demography) offers many benefits:
- It helps governments track whether economic growth is keeping up with population growth. Rapid population increase can lead to lower per capita income, unemployment, environmental strain, and pressure on social services.
- It supports better planning of social services such as schools, hospitals, water supply, electricity, and transport. For instance, knowing the number of children in each age group helps determine how many classrooms and teachers will be needed.
- Population data helps planners and policymakers forecast future trends and design effective policies on family planning, health, and economic development.
- It assists administrators in solving social and economic problems linked to population growth.
- It provides essential information for housing planning, urban development, and managing migration.
- In democratic systems, census data is used for drawing electoral boundaries, planning elections, and understanding voter demographics.
Population Distribution
Population distribution refers to how people are spread across the land. It is usually uneven because not all areas are suitable for living. Some places are sparsely populated (few people), while others are densely populated (many people).
Factors such as steep slopes, deserts, extreme weather, dense forests, or disease-prone areas often lead to low population. In contrast, fertile highlands, reliable water sources, and good economic opportunities attract more people.
Factors Governing Human Population Distribution
The way people are distributed on Earth is influenced by four major groups of factors:
- Physical factors (climate, relief, soil, water availability, etc.)
- Historical factors
- Economic factors (employment opportunities, agriculture, industries)
- Political factors
These factors together determine why some regions become crowded while others remain empty or sparsely settled.
Physical Factors
Physical factors play a major role in determining where people choose to live. These include relief (landforms), climate, soils, vegetation, drainage, pests and diseases, and the availability of water bodies.
Relief High-altitude areas (above 5,000 metres) are generally unsuitable for permanent settlement because of very low temperatures, reduced oxygen, and lower atmospheric pressure. On mountains like Kilimanjaro, both population numbers and density decrease as you go higher up the slopes. Most crops also stop growing well beyond 2,500 metres.
Rugged and hilly areas discourage settlement because building houses, roads, and railways is difficult and expensive. Farming is risky due to soil erosion and landslides. As a result, people prefer gentle, flat or rolling landscapes that make construction, transportation, and agriculture much easier.
Extremely flat areas can also be problematic due to poor drainage, waterlogging, and flooding. Sun-facing slopes (aspect) are often preferred in cooler regions because they receive more sunlight.
Climate Climate is one of the strongest influences on population distribution. It affects people directly and also influences soil, vegetation, and farming.
Extreme cold in high-latitude regions and extreme heat combined with dryness in deserts make life and agriculture very difficult, leading to sparse populations. Areas with reliable rainfall (especially over 1,000 mm per year) tend to support much higher population densities.
Soils Fertile soils, especially alluvial soils found in river valleys and deltas, can support dense populations because they are good for farming. Poor, infertile soils can only support small populations due to low agricultural productivity.
Vegetation Thick forests are usually sparsely populated because they make it hard to build roads and communication networks. They are also home to dangerous wildlife. In Tanzania, Miombo woodlands are often avoided because they harbour tsetse flies, which threaten both people and livestock.
Drainage Areas with good drainage attract settlement and farming, while swampy or flood-prone areas are generally avoided. Swamps are breeding grounds for mosquitoes, which spread malaria, and they also make building difficult.
Pests and Diseases Regions with many pests and diseases (such as mosquitoes and tsetse flies in tropical areas) tend to have fewer people. Tsetse flies cause sleeping sickness in humans and nagana in livestock, discouraging settlement.
Water Bodies Access to water is essential for drinking, irrigation, industry, and transport. River valleys are therefore heavily populated because they provide reliable fresh water.
Economic Factors
Economic opportunities strongly influence where people settle. The discovery of minerals or energy resources can create dense populations even in harsh environments. Mining towns often spring up in remote deserts, forests, or cold regions.
In Tanzania, diamond mining in Mwadui (Shinyanga) since 1940 has attracted thousands of job seekers and service providers. Trade, industries, and transport routes (roads and railways) also pull people toward towns and cities. Areas lacking industries or economic activities usually remain sparsely populated.
Historical Factors
History has left a lasting mark on population distribution. The 18th-century slave trade greatly reduced populations in many parts of East, Central, and West Africa as young people were captured or fled.
During colonial times, European settlers took the best farmland, pushing local people into reserves. This created uneven population patterns — sparse on former European farms and dense in the reserves — some of which still exist today.
Political Factors
Political instability, civil wars, and conflicts force people to flee, leaving some areas sparsely populated. Examples include refugees from Uganda under Idi Amin, Southern Sudan, and Somalia moving to neighbouring countries.
Government policies can also reshape population distribution. In Tanzania, the 1974 Villagisation (Ujamaa) policy moved people into villages to make it easier to provide schools, health services, and security. National parks and forest reserves are protected by law, so they remain sparsely populated.
Social Factors
People are attracted to places with good social services such as schools, hospitals, transport, and electricity. This is why urban areas are usually densely populated while many rural areas remain sparsely populated.
Population Change
Human population is constantly changing. Population change (or population growth) refers to the increase or decrease in the number of people in an area over a given period.
The three main factors driving population change are birth rate, death rate, and migration.
Birth Rate This is the number of live births per 1,000 people in a year. High fertility leads to higher birth rates. In Tanzania (1995–2000), the total fertility rate was 5.5 children per woman, and the Crude Birth Rate (CBR) was 40.2 births per 1,000 people.
Death Rate Also called mortality rate, this includes infant, child, and adult mortality. The Crude Death Rate (CDR) for Tanzania during the same period was 12.9 deaths per 1,000 people.
Natural Increase is calculated by subtracting the death rate from the birth rate. For example, Tanzania’s annual population growth rate was about 2.9% between 1988 and 2002.
Migration This is the movement of people from one place to another, which can be temporary or permanent. It includes immigration (moving in) and emigration (moving out).
Internal migration happens within a country (e.g., rural to urban). External (international) migration involves crossing borders.
Causes of Migration Common reasons include:
- Pressure on land
- Search for employment
- Desire to create wealth and better income
- Religious conflicts
- Political persecution
- Wars and civil unrest
- Natural calamities (drought, floods, diseases)
- Government policies and development projects
Effects of Population Change
On Individuals
- Large families from high fertility can strain parents, leading to poor health and inadequate care for children.
- Migration can bring positive changes like new skills, better income, and improved living standards.
- However, it can also cause family separation, delayed marriages, breakdown of marriages, loss of cultural values, or involvement in social problems.
On the Nation Rapid population growth can pressure resources, infrastructure, and the environment, but it can also provide a large workforce if well managed. Understanding these dynamics helps governments plan better for the future.\
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