Why are People Moving to Cities? (Crash Course Geography #45)
Urbanization is one of the most powerful and transformative geographic phenomena of the modern era. For most of human history, the vast majority of the global population lived in rural, agrarian settings. Today, following rapid industrialization, globalization, and economic restructuring, a majority of the human population lives in urban areas. This chapter explores the definition, evolution, patterns, and theoretical frameworks underlying urban geography.
1. The Global Shift: From Rural Roots to Urban Centers
- Diffusion and Spatial Analysis: In human geography, geographers love exploring diffusion—the spread of ideas, innovations, populations, and goods across space. Historically, trade routes like the Silk Roads and maritime commercial networks connected distant hubs, leaving behind powerful urban legacies.
- The Modern Urban Reality: According to United Nations estimates, people living in urban places now outnumber those in rural areas, a complete reversal from a century ago when less than one-third of the global population lived in cities.
- Case Study — Guangzhou and the Pearl River Delta:
- An ancient Chinese trading hub (known historically to Europeans as Canton), Guangzhou's population skyrocketed from about 2 million in 1980 to nearly 13 million in 2022.
- Driven by China's late-1970s "open door" policy, special economic zones, government infrastructure investments, and foreign capital, tranquil rural areas were rapidly transformed into factories, high-rises, and export processing zones.
2. Defining "Urban": The Core Challenge in Geography
Defining what constitutes an "urban" place is surprisingly complex because criteria vary significantly across countries, cultures, and regions.
- Criteria Used to Define Urban Settings:
- Population Numbers & Density: Absolute number of residents or concentration of people per square kilometer/mile.
- Infrastructure Development: Presence of paved roads, piped water, electricity grids, and commercial buildings.
- Type of Employment: A shift away from primary sector activities (agriculture, fishing, forestry) toward secondary, tertiary, and quaternary sectors (manufacturing, services, technology, finance).
- The Subfield of Urban Geography: A branch of human geography that investigates why towns and cities are located where they are, why some grow while others decline, how they are internally arranged, and how they interact with one another as points in space.
3. Classifying Urban Settlements by Scale and Function
Cities have evolved from ancient centers of political, economic, and social power into massive contemporary agglomerations. Geographers categorize urban settlements based on size, population density, and systemic function:
4. The Driving Forces of Urbanization: Policy, Economics, and Infrastructure
Urbanization is defined as the shift in the residence of a population from rural to urban areas. This massive demographic migration is accelerated by specific economic and political levers:
- Economic Restructuring: Cities act as the engines of economic development—a process that increases the complexity of an economy through diverse, specialized job markets.
- Jane Jacobs' Urban Insight: Noted urbanist Jane Jacobs argued that economic development does not merely happen to countries; rather, it is a dynamic process that happens in and through cities. Cities are economic entities defined primarily by their connections rather than static national borders (e.g., Shanghai is as closely tied to Singapore as it is to inland Chinese cities).
- Relaxation of Residency Laws: In places like China, the relaxation of internal migration controls (hukou reforms) allowed millions of rural citizens to move freely to urban centers, shifting the country's demographics from 70% rural in the 1990s to over 61% urban today.
- State and Global Capital Investment: Governments invest heavily in transportation, communication, and special economic zones to attract foreign investment, transforming rural agrarian land into industrial powerhouses almost overnight.
5. Urban Systems and Central Place Theory
To understand how cities interact across geographic space, geographers study urban systems—the structured ways in which cities of different sizes are interconnected within a regional or global network.
- Walter Christaller’s Central Place Theory (1930s):
- Core Premise: Explains the size, spacing, and distribution of settlements within an urban system based on consumer behavior and market economics.
- Central Places: Settlements centrally located to maximize accessibility for surrounding rural populations.
- Threshold and Range: A large number of small settlements (villages/towns) cluster closely together to provide low-order, everyday goods (like bread from a bakery). People travel much further, less frequently, to larger settlements for high-order, specialized goods and services (like specialized medical care or luxury items).
- The Idealized Model vs. Modern Reality: Christaller's model assumed a flat, uniform terrain with equal transportation access in all directions. Today, globalization has replaced isolated regional hierarchies with a global urban system, where world-class cities (New York, London, Tokyo) sit at the top of an interconnected international network regardless of geographic centrality.
6. Rank-Size Distribution vs. Urban Primacy
When examining the population hierarchy of cities within a country or region, geographers observe two primary distributional patterns:
- Rank-Size Distribution:
- In countries with high standards of living and balanced urban systems, settlements follow a predictable mathematical hierarchy.
- If the largest city has a population of , the second-largest city will be roughly , the third-largest , the fourth-largest , and so on.
- Urban Primacy (Primate Cities):
- In many parts of the world, this rule breaks down completely, resulting in a primate city—an urban center that is wildly disproportionate in size compared to any other city in the nation.
- Example: In Argentina (2022), Buenos Aires is roughly 10 times larger than Córdoba, the second-largest city. Primate cities concentrate a massive share of a country's economic, political, and cultural power.
7. The Colonial Origins of Primate Cities
- Historical Extraction: Most primate cities are found in low- and middle-income countries with histories of European colonization.
- Ports of Extraction: Colonial powers established coastal ports designed primarily to extract raw materials, minerals, and agricultural commodities (such as wool and cereals in Argentina) from the interior and ship them back to the colonizing nation.
- Lasting Legacy: Because colonial powers concentrated administration, trade infrastructure, and wealth into single primary ports, those hubs grew exponentially larger than secondary cities, cementing an imbalance that persists in modern national economies.
Summary and Key Takeaways
- Diffusion in Geography: Urban geography studies how urban spaces, ideas, and populations spread, evolve, and connect across space.
- Global Urban Majority: For the first time in human history, a majority of the global population lives in urban areas, with the UN projecting two-thirds of humanity will be urbanized by 2050.
- Definitional Complexity: Defining "urban" depends on local metrics, including population thresholds, population density, infrastructure development, and employment sectors.
- Scale Classifications: Cities range widely in scale from standard urban centers to mega cities (>10M), meta cities (>20M), and sprawling megalopolises (Boston-Washington D.C.).
- Jane Jacobs' Economic Principle: Economic development is fundamentally an urban process driven by cities acting as interconnected economic engines rather than isolated national entities.
- Central Place Theory: Walter Christaller's model explains that small settlements cluster for everyday needs, while larger settlements are spaced further apart to provide specialized, high-order goods.
- Rank-Size vs. Primacy: Balanced urban systems follow a predictable rank-size hierarchy, whereas many developing nations feature primate cities that dwarf all other regional settlements.
- Colonial Legacy: Many primate cities originated as colonial extraction ports, concentrating administrative power, transportation networks, and economic activity into a single dominant hub.
- Irreversible Trend: Driven by industrialization, technology, and service-based economies, global urbanization has become a permanent and accelerating fixture of the modern world.