The world population refers to the total number of people living on the Earth at a given time. As of the twenty-first century, the world population has crossed eight billion, and its distribution across the globe is highly uneven. More than 90 per cent of the world's population lives in only about 10 per cent of the land surface. The remaining 90 per cent of the land is either too hot, too cold, too dry or too mountainous to support dense settlement. Understanding the distribution, density and growth of the world's population is the foundation of population geography.
Population geography studies how people are spread over the Earth's surface, why they are concentrated in certain regions, and how their numbers change over time. Three key elements are used to describe population: distribution, density and growth. These elements are influenced by a combination of physical factors such as climate, soil, water and relief, and human factors such as economic development, technology, transport and historical events.
Population distribution is uneven because of the interplay of geographical, social, cultural and economic factors. The great concentrations of population are found in the monsoon lands of South and Southeast Asia, the mid-latitude river valleys of China, the industrial belts of Europe and the eastern coast of North America. In contrast, very sparse populations are found in the polar regions, the hot deserts of the Sahara, the dense equatorial forests of the Congo basin and the high mountain ranges of the Himalayas and the Andes.
More than half of the world's population is concentrated in Asia. The four major areas of dense population are East Asia (China, Japan, Korea), South Asia (India, Pakistan, Bangladesh, Sri Lanka), Southeast Asia (Indonesia, Thailand, Philippines) and Europe. These regions share certain common features: fertile soils, adequate rainfall, a favourable climate and a long history of agriculture and civilisation. The sparsely populated areas include the tropical rainforests, high-altitude regions, dry deserts and the cold polar regions, where survival is difficult.
Density of population is the ratio between the population and the area of a given region. It is usually expressed as the number of persons per square kilometre. Three types of density are commonly used. Arithmetic density is the number of people divided by the total land area. Physiological density divides the population by the arable (cultivable) land area, and agricultural density divides the number of farmers by the arable land area. These different measures reveal how much pressure population places on land resources.
Among the countries of the world, population density varies enormously. Small and densely populated countries such as Bangladesh have densities exceeding 1000 persons per square kilometre, while countries like Australia, Canada and Mongolia have densities of only a few persons per square kilometre. The density figures hide local variations: within a country, urban-industrial regions are far denser than rural or mountainous areas. Density therefore gives a better idea of the pressure of population on land than total population alone.
Growth of population is the change in population numbers over a period of time. It is measured either as natural growth or as overall growth. Natural growth is the difference between births and deaths in a region, while overall growth also includes migration. The rate of growth is usually expressed as a percentage per annum. The world population grew slowly for most of human history, but after the Industrial Revolution the rate of growth accelerated dramatically, a phenomenon called population explosion.
The growth of population can also be understood in terms of doubling time, which is the time required for a population to double at its current rate of growth. For example, if the growth rate is 2 per cent per year, the doubling time is about 35 years. The developing countries of Asia, Africa and Latin America have much higher growth rates than the developed countries of Europe and North America, where population has nearly stabilised. This contrast between high-growth and low-growth regions is a central theme in population geography.
Physical factors strongly influence where people live. Climatic regions with moderate temperatures and adequate rainfall, fertile alluvial soils of river valleys, availability of fresh water and gentle plains encourage dense settlement. Conversely, extreme climates, poor soils, steep mountain slopes and water scarcity discourage settlement. The Ganga plain, the Nile valley and the Yangtze valley are classic examples of river valleys with high population concentration.
Economic and social factors are equally important. Industrialisation, urbanisation, development of transport and communication, employment opportunities and better living standards attract people to particular areas. Conversely, political stability, government policies and historical migration influence population patterns. The growth of population itself depends on fertility, mortality and migration. Higher literacy, education of women and economic development generally lower birth rates, while poverty and lack of family planning keep birth rates high.
The world population remained below one billion until the early nineteenth century. It reached one billion around 1804, two billion in 1927, three billion in 1960, four billion in 1974, five billion in 1987, six billion in 1999 and seven billion in 2011. This rapid acceleration is due to the decline in death rates, improved healthcare, advances in medicine and the expansion of food production. The period from the 1950s to the 1970s witnessed the highest growth rates in human history.
In recent decades, the global growth rate has started to slow down because many countries have passed through their demographic transition. However, the absolute increase in population continues to be large because of the huge base population. The future growth of the world population will largely be determined by the demographic behaviour of developing countries, particularly those in South Asia and sub-Saharan Africa, where fertility rates remain relatively high.
The demographic transition model describes the stages through which a country passes as it moves from high birth and death rates to low birth and death rates. In the first stage, both birth and death rates are high, so population growth is slow. In the second stage, death rates fall rapidly due to better healthcare and food supply, while birth rates remain high, leading to rapid population growth. In the third stage, birth rates begin to decline and the rate of growth slows. In the fourth stage, both rates are low and population becomes nearly stable.
Developed countries such as those in Europe have completed all stages of the transition, while many developing countries are still in the second or third stage. The model helps explain why some regions experience population explosion while others face stagnation or even population decline. Critics point out that the model is based on the European experience and may not perfectly fit the demographic history of all developing countries.
| Region | Type of Area | Reasons |
|---|---|---|
| East Asia | High density | Fertile soils, monsoon climate, long history of agriculture |
| South Asia | High density | River plains, irrigation, dense agricultural settlements |
| Europe | High density | Industrialisation, temperate climate, urbanisation |
| Sahara Desert | Very low density | Extreme aridity, scarce water |
| Polar regions | Very low density | Extreme cold, ice-covered land |
| Amazon/Congo basins | Low density | Dense forests, difficult terrain, diseases |
| Type | Formula | What It Measures |
|---|---|---|
| Arithmetic Density | Total population / Total land area | Overall pressure of people on land |
| Physiological Density | Total population / Arable land | Pressure on cultivable land |
| Agricultural Density | Number of farmers / Arable land | Efficiency of agriculture |
The world population is distributed very unevenly over the Earth's surface. Dense clusters are found in the fertile river plains and industrial belts of Asia, Europe and eastern North America, while vast regions of desert, polar ice, high mountains and dense forests remain nearly empty. Density measures the pressure of population on land, while growth and doubling time describe the rate of change in population numbers. Both physical and economic factors determine where people live, and the demographic transition explains how countries move from high to low rates of growth. A clear understanding of these fundamentals is essential for the study of population composition, human development and the population problems of India in later chapters.
Keywords: World population, distribution, density, arithmetic density, physiological density, natural growth, doubling time, demographic transition.