Explain the processes of urbanisation and megacity growth and the challenges they create for people and environments

What this dot point is asking

QCAA wants you to explain how megacities grow and the challenges that growth creates. A megacity is an urban area with more than 10 million people. Urbanisation is the rising proportion of a population living in towns and cities. "Explain" means showing the processes (rural-urban migration, natural increase, reclassification) and then the challenges they produce for people and environments. This dot point sets up the Topic 2 investigation where you study one megacity in depth. Strong answers name a specific megacity, use real data, and link process to challenge.

The answer

Megacities and urbanisation

In 1950 only a couple of cities exceeded 10 million; by the 2020s there were more than thirty megacities, most in Asia and Africa. Urbanisation is the increasing share of people living in urban areas, distinct from urban growth (the absolute rise in city population). The fastest urbanisation is now in the global south, where cities are growing far faster than the European and North American cities did during their industrial era, and with far less time and resource to build infrastructure.

Process 1: rural-to-urban migration

The classic driver is migration from countryside to city, propelled by push factors (rural poverty, lack of land, mechanised agriculture, drought) and pull factors (jobs, services, education, the perception of opportunity). Lagos and Dhaka draw millions of rural migrants seeking work, often arriving faster than formal housing and jobs can absorb them.

Process 2: natural increase

Many megacity populations are young, with high birth rates, so the city grows from within through natural increase (births minus deaths) as well as from migration. In rapidly growing African and South Asian cities, internal natural increase now contributes as much growth as migration.

Process 3: reclassification and expansion

As cities sprawl, formerly rural settlements on the edge become absorbed into the urban area and reclassified as urban. This statistical and physical expansion adds to measured city population without new migration, and it consumes farmland and natural land cover on the fringe.

Challenges for people

Rapid growth outpaces the capacity to house and service people, producing:

• Informal settlements (slums). A large share of megacity residents in the global south live in informal housing without secure tenure, often built on hazard-prone land. Dharavi in Mumbai and the informal settlements of Lagos are large examples.
• Inadequate services. Water, sanitation, electricity, health and education struggle to keep pace, raising disease risk.
• Congestion and transport stress. Jakarta is notorious for severe traffic congestion that costs hours and billions in lost productivity.
• Inequality. Wealthy enclaves sit beside informal settlements, with sharp differences in access to services.
• Employment in the informal economy. Many migrants work in insecure, unregulated informal jobs.

Challenges for environments

• Water and sanitation. Demand outstrips supply; Jakarta's over-extraction of groundwater is causing the city to subside, with parts sinking and flooding.
• Air pollution. Delhi suffers among the world's worst air quality, driven by traffic, industry, construction and crop burning.
• Land cover loss. Sprawl converts farmland, wetland and bushland to built surfaces, increasing flood risk and heat.
• Waste. Solid waste and untreated sewage overwhelm systems.
• Hazard exposure. Informal settlements on floodplains, steep slopes and coasts expose poor residents to flooding and landslides, a vulnerability worsened by climate change. Dhaka faces severe flood and cyclone exposure.

Linking process to challenge

The analytical move is connecting growth process to challenge. Rapid in-migration plus natural increase (process) outstrips housing supply, producing informal settlements (challenge). Sprawl and reclassification (process) destroy fringe land cover and push settlement onto hazard-prone land (challenge). This sets up Topic 2, where you propose management action for one challenge in a chosen megacity.

Examples in context

Example 1. Lagos. Rapid rural-to-urban migration and high natural increase produce explosive growth, large informal settlements and severe infrastructure pressure.

Example 2. Jakarta. Over-extraction of groundwater for a megacity population causes land subsidence and worsening coastal flooding, prompting plans to relocate the capital.

Example 3. Delhi. Traffic, industry, construction and surrounding crop burning combine to give the megacity some of the world's most hazardous air quality, a direct people-and-environment challenge of rapid growth.