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Quiz yourself on Urban Sustainability and MegacitiesGet your flashcardsBuild my revision planTrack my progress🔍 Why Do Megacities Grow? The Push-Pull Model
Megacities do not grow simply because people are born in them. They grow primarily because people migrate to them from rural areas — a process called rural-urban migration. To understand why, geographers use the push-pull model: a framework that distinguishes between factors that drive people away from the countryside (push factors) and factors that attract them towards the city (pull factors).
Push and pull factors always operate together. A farmer whose harvest has failed (a push factor) will not necessarily move to the city unless she believes the city offers something better (a pull factor). The decision to migrate is rational — people weigh the costs and benefits, gather information from family members who have already moved, and make a calculated choice about where their livelihood is most secure.
As tractors and combine harvesters replace manual labour, fewer workers are needed on farms. In Bangladesh, the spread of mechanical rice threshers eliminated thousands of jobs in rural areas from the 1990s onwards. Agricultural workers who cannot find seasonal employment are pushed towards the city, where they hope to find work in factories or the service sector.
Floods, droughts, and cyclones can destroy harvests, damage homes, and contaminate water supplies. In Bangladesh — where 70% of the land sits less than 1 metre above sea level — annual flooding is becoming more severe and unpredictable with climate change. Families who lose their livelihoods to flooding may have no option but to move to the city. This is sometimes called climate migration or environmentally induced migration.
Rural areas in LICs typically have fewer schools, hospitals, and reliable electricity than urban areas. Parents who want their children to access secondary or university education may move to the city to give them that opportunity. Families with sick relatives may move to be near hospitals. The absence of services is a structural push factor that accumulates across generations.
In some regions, armed conflict, land seizures, or ethnic violence forces displacement. Many of the fastest-growing African cities — including Kinshasa and Mogadishu — have experienced rapid growth partly driven by people fleeing rural conflict. This "forced urbanisation" is distinct from economic migration but adds to the same pressure on urban infrastructure.
Urban workers in LICs typically earn 3–5 times more than rural workers doing similar hours. A garment factory worker in Dhaka earns approximately $95 per month — modest by international standards, but far more than agricultural day labour in rural Bangladesh. The wage differential is the single most powerful factor drawing migrants to megacities.
Cities concentrate investment. Dhaka has universities, specialist hospitals, reliable electricity, and piped water — none of which are available across rural Bangladesh. The city offers life chances that the village cannot.
Migration is rarely a solo decision. When a family member or neighbour has already moved successfully to the city, they provide information, contacts, and sometimes accommodation for new arrivals. These social networks — sometimes called chain migration — make the move feel safer and more achievable, and they accelerate urban growth as each successful migrant becomes a beacon for others.
Cities grow → more services and jobs are created → more people are pulled in → the city grows further. Rural areas simultaneously lose their young, skilled workers → services deteriorate → more people are pushed out. This dynamic explains why megacity growth is not linear but accelerating.
Quick Check: Give two push factors and two pull factors that explain rural-urban migration to megacities in LICs.
Push factors (from rural areas): 1. Mechanisation of farming — tractors and harvesters replace manual workers, removing agricultural livelihoods. 2. Natural disasters/climate change — flooding in Bangladesh destroys harvests and forces displacement. Also accept: lack of rural services (schools, hospitals); conflict and political instability. Pull factors (to the city): 1. Higher wages — urban workers earn 3–5× more than rural workers. 2. Better services — cities have schools, hospitals, reliable electricity not available in rural areas. Also accept: social networks/chain migration; diverse employment opportunities.
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