The World Population: Distribution, Density and Growth

The global distribution of human population is characterized by extreme spatial inequality:
1. Concentration in Fertile River Valleys: Human beings concentrate in flat alluvial river plains (Ganga-Brahmaputra in India, Yangtze in China, Nile in Egypt) where fertile soil, abundant freshwater, and warm climates support intensive food agriculture and urban industrial clusters.
2. Avoidance of Harsh Environments: Over 70% of Earth's land surface consists of inhospitable physical terrain—scorching hyper-arid deserts (Sahara, Kalahari), sub-zero frozen polar tundra (Antarctica, Greenland, Siberia), dense equatorial rainforests (Amazon), and rugged high mountain peaks (Himalayas, Rockies)—where cold, drought, or steep slopes make human survival extremely difficult.

• Arithmetic Population Density: The ratio between the total number of people living in a territory and the total geographic land area of that territory, expressed in persons per square kilometer ($persons/km^2$):

$$\text{Density} = \frac{\text{Total Population}}{\text{Total Land Area}}$$

• Calculation:

$$\text{Population} = 10,000,000 \text{ persons}, \quad \text{Area} = 25,000 \text{ km}^2$$

$$\text{Density} = \frac{10,000,000}{25,000} = \mathbf{400 \text{ persons / km}^2}$$

Conclusion: The region is densely populated with an average of 400 persons per square kilometer.

1. Water Availability: People settle where freshwater is readily available for domestic use, livestock, irrigation, and river navigation. Desert oases and river valleys are densely settled.
   2. Landforms / Relief: Flat plains and low coastal valleys attract dense populations because they facilitate intensive farming, road construction, and industrial factories. Steep mountain slopes hinder transportation and agriculture, remaining sparsely populated.
   3. Climate: Comfortable climates with moderate seasonal temperatures (like Mediterranean Europe or the monsoon plains of Asia) attract massive populations. Extreme climates (freezing Arctic, blistering Sahara) discourage human settlement.
   4. Soils: Deep, fertile alluvial and volcanic soils support high-yield multiple cropping, sustaining dense human settlements (e.g., Northern Plains of India, volcanic Java in Indonesia).

• Push Factors: Unfavorable, negative, or coercive conditions at the Place of Origin that make life intolerable, compelling people to emigrate and leave their homes.
Examples: (1) Severe agricultural unemployment and poverty; (2) Natural disasters, droughts, and famines; (3) Political persecution, ethnic violence, and civil war.
• Pull Factors: Attractive, advantageous, and beneficial conditions at the Place of Destination that entice and draw migrants from distant areas.
Examples: (1) High-paying jobs and economic opportunities; (2) Political peace, security of life, and civil liberties; (3) Superior universities, healthcare systems, and pleasant climate.

The Demographic Transition Theory describes the transformation of a society from high birth and death rates to low birth and death rates as it modernizes:
1. Stage 1 (High Fluctuating): Characterized by high birth rates and high death rates (both $>35/1000$). Epidemics, famines, and lack of healthcare cause death rates to fluctuate violently. Population growth is slow and stagnant; life expectancy is very low.
2. Stage 2 (Expanding / Population Explosion): Modern medicine, sanitation, and clean water cause death rates to plummet rapidly, while birth rates remain stubbornly high due to traditional cultural norms. The wide gap between births and deaths triggers a colossal population explosion (e.g., developing nations).
3. Stage 3 (Low Fluctuating): As society becomes urbanized, educated, and uses family planning, birth rates drop to match low death rates. Population stabilizes or begins contracting, leading to an aging population (e.g., Japan, Germany).

In 1798, English clergyman Thomas Malthus predicted an inevitable demographic catastrophe:
• Malthusian Theory: Human population expands geometrically (1, 2, 4, 8, 16, 32...), whereas food production can increase only arithmetically (1, 2, 3, 4, 5, 6...).
• He warned that unless humans controlled reproduction through "preventive checks" (chastity, late marriage), nature would impose brutal "positive checks" (famines, plagues, wars) to restore balance.
• How Technology Disproved Malthus: Malthus failed to foresee the Agricultural and Industrial Revolutions (mechanized tractors, synthetic chemical fertilizers, high-yielding hybrid seeds, and biotechnology), which expanded global food production at a rate far outstripping arithmetic growth, feeding 8 billion people today.

• Industrialisation: Industrial factory belts create an enormous diversity of employment opportunities—not just for factory workers, but for transport drivers, accountants, bank officers, and retailers. A prime global example is the Kobe-Osaka industrial region in Japan, which attracted millions of residents because of its concentration of steel and textile mills.
• Urbanisation: Modern cities provide superior educational institutions, advanced medical hospitals, reliable electricity, digital internet connectivity, and diverse cultural entertainment, acting as a massive pull factor drawing rural migrants seeking a higher quality of life.

• Natural Growth Rate: The net change in population resulting strictly from biological births and deaths within an accounting year, calculated as:

$$\text{Natural Growth} = \text{Crude Birth Rate (CBR)} - \text{Crude Death Rate (CDR)}$$

• Actual Population Growth: Incorporates both natural biological change PLUS spatial migration:

$$\text{Actual Growth} = (\text{Births} - \text{Deaths}) + (\text{Immigration} - \text{Emigration})$$

A country can have a negative natural growth rate (deaths exceed births) but still experience positive actual population growth if immigration is sufficiently high (e.g., Canada).