The World Population: Distribution, Density and Growth

Introduction

The study of world population is central to human geography. Understanding where people live, how densely they are settled, and how fast populations are growing or declining helps governments and planners manage resources, services, and development. The world population crossed 8 billion in 2022, and this number continues to change, though growth rates vary enormously across regions.

Distribution of World Population

Population distribution refers to the way people are spread across the Earth's surface. It is highly uneven — some areas are extremely densely populated while others are almost empty.

• Densely Populated Regions:
• East Asia — China, Japan, Korean Peninsula; favourable climate, fertile river valleys.
• South Asia — Indian subcontinent (India, Bangladesh, Pakistan); monsoon climate, river plains.
• North-West Europe — UK, Germany, France; industrial revolution legacy, temperate climate.
• North-East USA — Boston-Washington corridor; economic development, historical settlement.
• South-East Asia — Indonesia, Philippines, Vietnam; monsoon climate, rice cultivation.

• Sparsely Populated Regions:
• High latitude areas — Arctic, Antarctica (extreme cold)
• Hot deserts — Sahara, Arabian Desert, Atacama (water scarcity)
• Equatorial rainforests — Amazon Basin, Congo Basin (dense forests, diseases)
• High mountain areas — Himalayas, Rockies, Andes (rugged terrain, thin air)

Factors Affecting Population Distribution

• Physical Factors:
• Climate — Moderate, humid climates attract more people; extreme climates repel.
• Landforms — Plains and river valleys are preferred; mountains are avoided.
• Soils — Fertile soils (alluvial, volcanic) support dense agricultural communities.
• Water — Proximity to rivers, lakes, or coastal areas encourages settlement.
• Natural resources — Mineral-rich areas attract industrial settlements.

• Human/Social Factors:
• Historical settlements — Old civilisations grew in fertile river valleys (Nile, Ganga, Yangtze).
• Industrialisation — Industrial centres pull migrants seeking employment.
• Urbanisation — Cities concentrate people through economic opportunity.
• Political stability — Peaceful regions attract more settlers.

Population Density

Population density measures the number of people per unit area of land.

Formula: Population Density = Total Population / Total Area (km²)

• Types of Density:
• Arithmetic Density — Total population divided by total land area.
• Physiological Density — Total population divided by cultivable land area. (More meaningful for agricultural societies.)
• Agricultural Density — Number of farmers divided by cultivable land area.

Global average density is about 60 persons per km², but ranges from near 0 (Antarctica) to over 1000/km² in city-states like Bangladesh (overall ~1100/km²).

Population Growth

Natural Growth Rate = Birth Rate - Death Rate
(expressed per 1000 persons per year)

Actual growth also includes migration (immigration minus emigration).

• Key Terms:
• Birth Rate (CBR) — Number of live births per 1000 people per year.
• Death Rate (CDR) — Number of deaths per 1000 people per year.
• Natural Increase Rate (NIR) — CBR minus CDR.
• Infant Mortality Rate (IMR) — Deaths of infants under 1 year per 1000 live births.

Historical Trends in World Population

• For most of human history, population grew very slowly (famine, disease, wars).
• After the Industrial Revolution (18th century), death rates dropped due to better medicine and food supply, while birth rates remained high — this triggered rapid population growth.
• The demographic transition from high birth/death rates to low birth/death rates describes how populations evolve as countries develop.

• Demographic Transition Model (DTM) — 4 Stages:
• Stage 1: High birth rate, high death rate — slow growth (pre-industrial societies).
• Stage 2: High birth rate, falling death rate — rapid growth (early developing nations).
• Stage 3: Falling birth rate, low death rate — slowing growth (developing nations).
• Stage 4: Low birth rate, low death rate — near-zero or negative growth (developed nations).

Doubling Time

Doubling time is the number of years it takes for a population to double at a given growth rate.

Rule of 70: Doubling Time (years) = 70 / Annual Growth Rate (%)

Example: At a 2% growth rate, doubling time = 70 / 2 = 35 years.

Population Composition

While not the focus of this chapter, population composition (age, sex, literacy, occupation) provides further dimensions. The age-sex pyramid is a key tool to represent this visually.

• Do not confuse population distribution (where people live) with population density (how many per km²).
• Arithmetic density divides by total area; physiological density divides by cultivable area — they give different results and meanings.
• High birth rates alone do NOT cause rapid growth — growth is driven by the gap between birth and death rates.
• Equatorial rainforests are sparsely populated NOT because of heat alone, but because of dense vegetation, poor soils for agriculture, and disease.

World population distribution is highly uneven, concentrated in South Asia, East Asia, Europe, and the eastern USA. Physical factors (climate, landforms, soils, water) and human factors (history, industrialisation, economy) explain these patterns. Population density can be measured arithmetically or physiologically. Growth is determined by birth rates, death rates, and migration. The demographic transition model explains how populations change as societies develop, moving from high birth/death rates to low birth/death rates.