IB Geography G.4.1 Urban Growth Projections for 2050 Notes

Urban Growth to 2050: Most New Urban Residents Will Be in Asia and Africa

1. Urbanization is an increase in the proportion of a population living in urban settlements.
2. Urban growth is an increase in the number of people living in towns and cities.
3. A country can experience urban growth while its urbanization rate changes little if rural and urban populations rise together.
4. A highly urbanized country can also have slow urban growth because most of its population already lives in cities.
5. The distinction prevents students from treating population size and urban share as the same measure.
6. The United Nations 2018 projection places the global urban share at about 68% by 2050, up from 55% in 2018.
7. The same projection assigns close to 90% of the increase in the urban population to Asia and Africa.
8. These are projections based on assumptions about fertility, mortality, migration and settlement classification, rather than fixed predictions.

Regional Patterns: Rapid Growth Starts from Unequal Urban Baselines

1. Africa has the lowest regional urban share but some of the fastest rates of urban population growth.
2. A low starting share means a large rural population remains available for future rural to urban migration.
3. High fertility and a young age structure also produce natural increase within African cities.
4. Growth is spread across megacities such as Lagos and many smaller urban centres that receive less international attention.
5. Asia already contains the largest urban population in absolute terms, so even a slower percentage increase adds very large numbers.
6. Industrial corridors, service employment and coastal economic zones continue to draw people toward urban labour markets.
7. China is highly urbanized compared with South Asia, while India retains a much larger rural population and therefore a longer urban transition.
8. Europe is already highly urbanized and has slow population growth, so its urban share is expected to rise only gradually.
9. Some European cities will grow through international migration while others face population loss and ageing.
10. Northern America is also highly urbanized, with much change taking the form of suburban expansion, densification and metropolitan redistribution.
11. Latin America and the Caribbean reached high urban shares earlier than most of Asia and Africa.
12. Future change there concerns the quality, inequality and environmental cost of urban growth as much as the speed of urbanization.
13. Oceania combines highly urbanized Australia and New Zealand with smaller island states whose urban systems face different climate and capacity limits.

Urban Populations Grow Through Migration, Natural Increase and Reclassification

1. Rural to urban migration moves people toward urban jobs, education, healthcare, transport and social networks.
2. Low rural incomes, insecure farming, land pressure and weak services can strengthen the push from rural areas.
3. Migration is age selective because young adults are more likely to move than children or older people.
4. This selectivity can enlarge the working-age population of the destination city and accelerate household formation.
5. Natural increase occurs when births exceed deaths within the existing urban population.
6. Its contribution rises after earlier migrants settle, form families and have children in the city.
7. Falling death rates can maintain rapid growth even when fertility begins to decline.
8. Natural increase therefore explains why stopping migration would not stop urban growth in many youthful cities.
9. Reclassification occurs when a settlement crosses a national urban threshold or when a city boundary expands around nearby settlements.
10. Reclassification changes the recorded urban population without requiring anyone to move.
11. Countries use different urban definitions, so comparisons must check whether the data use population thresholds, density, administrative status or economic activity.

City Sizes Will Diverge: Small and Medium Cities Matter Alongside Megacities

1. Megacities contain at least 10 million residents and will become more numerous by 2050.
2. Their absolute size creates large demands for housing, mass transit, water, power and waste management.
3. Agglomeration can raise productivity because firms, workers and services are close together.
4. The same concentration increases exposure when floods, heatwaves, earthquakes or infrastructure failures affect millions at once.
5. The fastest proportional growth often occurs in small and medium urban settlements with fewer than one million residents.
6. These centres absorb migration from nearby rural areas and connect farmers to regional markets.
7. Their governments often have smaller tax bases and weaker planning capacity than national capitals.
8. A modest numerical increase can therefore overwhelm local roads, drainage and land administration.
9. Urban corridors may form when neighbouring cities expand along transport routes and begin to share labour and housing markets.
10. Metropolitan growth can cross municipal boundaries, so one functional city may be governed by several authorities.

Age and Household Structures Change the Services Cities Need

1. High-income cities commonly have low fertility, long life expectancy and an ageing population.
2. They need accessible public transport, nearby healthcare, adapted housing and cooling plans for older residents.
3. A shrinking workforce can increase demand for labour migration and automated services.
4. Single-person households can keep housing demand high even where population growth is slow.
5. Lower-income cities commonly have younger populations and faster household formation.
6. They need large additions to schools, entry-level jobs, affordable housing, water and sanitation.
7. A young population can support a demographic dividend if education and formal employment grow fast enough.
8. Without those conditions, underemployment and informal work can expand alongside the city.
9. Migration can make the urban age structure younger than the national structure because movers are concentrated in working ages.
10. Gender ratios may also change where particular industries recruit men or women selectively.
11. Household size often falls with rising incomes, but housing demand can still rise because more households occupy separate dwellings.

Projection Quality Depends on Assumptions and Geographic Scale

1. A projection starts from a base population and applies assumptions about births, deaths and migration.
2. Small changes in each assumption compound over several decades and widen the range of possible outcomes.
3. National economic growth may increase cityward migration, while recession or conflict may redirect flows.
4. Climate change can damage rural livelihoods but can also make exposed coastal cities less attractive.
5. Administrative boundaries may understate a city region when built-up growth spreads beyond the official municipality.
6. Satellite imagery can reveal physical expansion, while census data show the people and household structures within it.
7. A percentage map is useful for comparing urban shares, while proportional symbols are better for comparing absolute urban populations.
8. A time series shows the pace of change, but it should not be extended beyond the data without explaining the assumption.
9. Scenario ranges are more honest than a single precise number when future migration or fertility is uncertain.
10. Urban planning should therefore test more than one population and climate scenario.

Urban Growth Changes Land, Housing and Infrastructure at Different Speeds

1. Land conversion spreads built surfaces across farmland, wetlands and peri-urban settlements.
2. Low-density expansion consumes more land and lengthens water pipes, roads and power lines for each additional resident.
3. High-density growth uses land more efficiently but can raise crowding and heat exposure if open space and ventilation are lost.
4. Housing supply often responds more slowly than population because land assembly, finance and construction take time.
5. When formal housing is unaffordable, households may subdivide rooms, occupy peripheral land or build informal settlements.
6. Peripheral housing can appear cheap while imposing high transport costs and long journeys to work.
7. Secure tenure can support household investment, but formalisation may also raise rents or taxes.
8. Water and sanitation require both network capacity and connections that households can afford.
9. A new treatment plant does not improve health if pipes do not reach fast-growing districts.
10. Storm drains must be planned with land cover because paving increases runoff at the same time as exposure grows.
11. Transport demand rises as homes and jobs spread across a larger metropolitan area.
12. Mass transit can move large flows efficiently when routes, fares and land use are coordinated.
13. Road expansion alone may encourage more driving and produce renewed congestion.
14. Employment structure may shift toward services, construction and informal work as the urban population expands.
15. Formal job creation may lag behind the working-age population even when total city output rises.
16. Agglomeration benefits are strongest when workers can reach jobs and firms can access reliable power, transport and communications.
17. Governance capacity determines whether boundaries, budgets and planning powers match the functional urban region.
18. A municipality may collect taxes in the centre while population growth occurs in surrounding authorities.
19. Shared metropolitan bodies can coordinate transit, housing and drainage across those boundaries.
20. Participatory mapping can reveal informal services and hazards that administrative records miss.

Urban Growth Scenarios Produce Different Spatial Futures

1. Compact-city scenario: Most additional residents are housed through infill, redevelopment and higher density near existing services.
2. This can shorten journeys and protect surrounding farmland, but it may intensify land prices and heat without affordable housing and green space.
3. Peripheral-expansion scenario: New neighbourhoods spread beyond the existing built edge where land is cheaper.
4. This can increase housing supply but lengthens networks and may convert farmland, wetlands or hazard-prone land.
5. Polycentric scenario: Several centres share jobs, services and transport demand instead of concentrating every function in one core.
6. Secondary centres can reduce cross-city journeys if housing and employment grow together.
7. Corridor scenario: Urban growth follows railways, highways or coastlines and links previously separate settlements.
8. Linear growth can support transit but also concentrates exposure where a single route or coast is disrupted.
9. Decline scenario: Population loss leaves excess housing and infrastructure in some districts.
10. Shrinking cities may need to consolidate services and reuse vacant land rather than plan only for expansion.
11. Scenario maps help planners compare land take, travel, service cost and hazard exposure before committing to one path.
12. The preferred pattern depends on geography, land ownership, governance and the distribution of future jobs.

Planning for 2050 Means Matching Capacity to the Pattern of Growth

1. Compact growth can reduce travel distances and infrastructure length, but high land prices can displace low-income residents.
2. Planned expansion can reserve land for transit, drainage, schools and affordable housing before prices rise.
3. Upgrading informal settlements can improve safety and services without breaking livelihoods and social networks through mass relocation.
4. Metropolitan coordination is needed where commuters, water systems and housing markets cross local government boundaries.
5. Smaller cities need finance and technical capacity because rapid proportional growth can arrive before their institutions are ready.
6. Ageing cities need to retrofit existing neighbourhoods, while youthful cities must build large amounts of new social infrastructure.
7. The most useful plan connects the projected number of residents to where they will live, their likely age structure and the systems they will use.