What the projections show

Urban growth means an increase in the number of people living in urban areas. Urbanization means an increase in the proportion of a population living in urban areas. If the rural population grows equally quickly, a country can experience urban growth without increasing its urban share.

The UN's 2018 World Urbanization Prospects projected that about 68% of the world's population would live in urban areas by 2050, compared with 55% in 2018. It anticipated roughly 2.5 billion additional urban residents. Nearly 90% of that increase was expected to occur in Asia and Africa. These projections depend on assumptions; they aren't guaranteed outcomes.

Asia is expected to retain the largest urban population. Africa, meanwhile, experiences particularly rapid urban growth from a lower urbanization level. Europe, Northern America, and Latin America and the Caribbean already have high urban shares, so their proportional increases are generally smaller. In Oceania, strongly urbanized countries sit alongside smaller island states with different settlement patterns.

Migration and other sources of growth

Rural–urban migration is the movement of people from rural areas to urban areas. Migrants are attracted by employment, education and services. Insecure rural livelihoods, land pressure and environmental stress can encourage them to leave.

Urban growth doesn't come from migration alone. When births exceed deaths, urban populations increase. Settlements can also expand or be reclassified, bringing previously rural residents inside an urban boundary. Transport links and communication networks help migrants stay connected with their places of origin.

Changing sizes and structures

Growth is not confined to megacities, which have at least ten million inhabitants. Smaller and intermediate cities absorb large numbers of residents too, often without the financial resources of major metropolitan centres. As metropolitan areas expand, they can incorporate neighbouring towns and spread beyond their administrative boundaries.

Population size is only part of the change. Migration commonly increases the number of young working-age adults, followed by family formation and demand for schools and housing. In many slower-growing cities, ageing increases demand for accessible transport, adapted housing and health services. Selective migration can also change household composition and cultural diversity.

Planning for 2050 requires more than an estimate of total population. Planners also need to consider residents' age profile, household needs and spatial distribution. Fertility, migration policy, conflict and economic change can all shift the projected outcome.

Resilience means maintaining essential functions

A resilient city can withstand disruption and keep essential services running, then recover and adapt to future risks. Resilience isn't about preventing every hazard. It means reducing the likelihood that a shock turns into a prolonged urban crisis.

More severe heat, flooding, drought and coastal inundation are climatic risks. As cities expand, they can increase exposure by placing people and infrastructure in hazardous locations. Geopolitical risks include armed conflict, terrorism and forced displacement, as well as disruption to international supplies of energy or food.

Strategies and their limits

• Reduce exposure: restrict development in flood-prone areas. Protect essential facilities and provide safe evacuation routes.
• Adapt buildings and public space: reduce heat and flood impacts through shade and ventilation, permeable surfaces and floodwater storage.
• Build redundancy: use backup power, multiple supply routes and decentralized services instead of relying on one vulnerable facility.
• Strengthen preparedness: combine early warnings, shelters and emergency plans with coordination between authorities and communities.

Vulnerability is unequal, and measures must address this. Without assistance, residents with insecure housing, limited mobility or low incomes may be unable to evacuate or recover. Protective infrastructure needs maintenance too. Events beyond its design capacity may overwhelm it.

Two illustrative examples

The class chooses its own two detailed examples. Each should link a specific risk to a strategy and explain how that strategy works. Its coverage and limitations should also be considered.

Rotterdam, Netherlands — climatic resilience. Low-lying urban land is exposed to flood risk. At Benthemplein, the city's water square serves as everyday public space while also providing temporary storage for heavy rainfall. This reduces pressure on drainage systems. Green roofs can retain rainwater and reduce heat too. These measures complement larger flood defences, but they have finite storage capacity. They cannot replace protection against every type of flooding.

Kyiv, Ukraine — geopolitical resilience. Wartime attacks on energy infrastructure show how damage outside a neighbourhood can interrupt services within it. Underground metro stations provide shelter. During outages, backup generators and emergency support points help sustain essential services. These measures reduce immediate disruption, but they depend on fuel and equipment, staffing and safe access. They do not remove the underlying conflict.

Reducing the demands a city places on the environment

An eco city is an urban settlement designed or managed to reduce environmental damage and resource use. Green buildings alone don't determine its performance. How residents actually live and how services operate matter too.

An ecological footprint measures the biologically productive land and water area needed to supply a population's consumption and absorb its wastes, particularly carbon dioxide, using prevailing technology. The measure extends beyond the city boundary: it includes land producing imported food or supporting energy consumption.

Environmental strategies

Compact, mixed-use development can shorten journeys and support public transport, walking and cycling. Density has limits, though. Without adequate green space or ventilation, it can intensify heat and reduce environmental quality.

Efficient buildings reduce energy demand and emissions, alongside renewable energy and low-carbon heating. Conserving water, controlling leakage and reusing water reduce pressure on supplies. Repair and reuse reduce demand for new materials and lower waste disposal requirements, as do recycling and composting.

Urban vegetation can provide shade and retain rainfall. It also supports biodiversity. These benefits complement reductions in resource consumption; planting trees alone cannot compensate for high fossil-fuel use or excessive material demand.

Two illustrative examples

The class chooses its own two detailed examples. For each, explain the environmental strategy and how it reduces the footprint. Include any limits to its effectiveness.

Freiburg, Germany — Vauban district. Energy-efficient housing combines with tram access and cycling routes, while many residential streets restrict car access. Together, these measures link building design with transport planning. Lower heating demand and fewer car journeys can reduce energy use and emissions. The district does not represent every part of Freiburg, however. Construction materials and residents' wider consumption still contribute to its footprint.

Curitiba, Brazil — transport and land-use integration. Bus rapid transit corridors link to relatively dense development, making public transport accessible to more residents. Moving people efficiently along these corridors can reduce reliance on private cars and limit transport-related land and energy demands. Floodable parks combine recreation with water management. For the transport benefits to be effective, fares must be affordable and capacity adequate, with access from peripheral neighbourhoods. Even a successful network does not eliminate all congestion or emissions.

Using information to operate urban systems

A smart city uses connected technology and data to monitor urban services, coordinate them and improve how they work. The technology helps manage the city. Its presence alone does not show that a city is sustainable or inclusive.

Traffic signals can respond to congestion, while public transport systems provide information to passengers. Other applications include electricity grids that balance supply and demand, street lighting that responds to use, and waste collection timed to how full containers are. Residents can also use digital platforms to report faults or access services.

Purpose-built settlements

A purpose-built settlement is planned and constructed as a new urban development. Planners can design digital networks and utility systems alongside transport from the outset. This avoids some of the difficulties caused by older infrastructure.

Initial costs are substantial. There is also a risk that planners design for an idealized population rather than real residents. Even a technically advanced settlement may be environmentally costly if it requires long car journeys or extensive new construction. Exclusive housing can restrict who benefits, too.

Retrofitting older settlements

Retrofitting means adding new systems or improving existing ones within an established settlement. It might involve installing smart meters or adding sensors to water pipes. Existing public transport can also be connected to real-time information platforms.

There’s no need to build a new city for retrofitting to benefit an existing population, and the work can happen in stages. Old networks and incompatible equipment can raise costs, as can disruption during installation. If investment is uneven, poorer neighbourhoods may be left with less reliable services.

Conditions for success

For smart services to work, electricity and communications must be reliable. They also require skilled maintenance and secure data management. Cyberattacks or system failures can create new vulnerabilities. Privacy safeguards matter, as does non-digital access: not every resident has a smartphone or reliable internet access, and some cannot use an app.

Cities change through connections with other places

Spatial interactions are movements and connections between places, including flows of people, goods, money and information. Connections with other places help shape urban growth and restructuring; events within the city are only part of the story.

Economic interactions

Investment from elsewhere can create employment and expand infrastructure. It can also increase demand for housing. Through trade and supply chains, urban firms reach markets and access resources, while tourism and service exports bring income. Better transport can strengthen these links and extend a city's commuting area.

These effects can reverse. When production moves abroad, a factory closure may reduce employment. It may also encourage out-migration and leave industrial land unused. A city that depends on imported energy or a narrow export market can be exposed to distant disruption. Digital connectivity can attract new activities, though the benefits do not reach all neighbourhoods equally.

Demographic interactions

Migration changes population size as well as composition. Arriving working-age adults may expand the labour force and increase demand for rental housing. Family migration increases demand for schools and other services. Refugee movements can bring rapid changes that planners had not anticipated.

In the place of origin, out-migration may accelerate ageing. Remittances link urban migrants with other settlements: they support household spending and sometimes property investment elsewhere. Commuting separates where people work from where they live. The functional urban area can therefore expand without matching changes to administrative boundaries.

Change through time

Economic and demographic interactions reinforce one another. New employment attracts migrants; a larger population supports more services. Improved connections then attract further investment. Job losses and out-migration can likewise reinforce decline. Sustainable management must therefore consider the wider urban network and how those relationships may change.

Separate the size of a change from its rate

A large city can gain many residents even with a modest percentage growth rate. In a small city, rapid percentage growth may add fewer people. To understand the pressure on an urban system, look at both absolute and proportional change.

The starting position matters too. A city with spare housing and reliable utilities faces a different challenge from one where services already fall short when more residents arrive. Whether it can accommodate growth depends on governance, revenue and the capacity to maintain services.

Different urban trajectories

• Rapidly growing cities may struggle to provide serviced land, affordable housing, transport, water and sanitation quickly enough. When expansion is unplanned, commuting distances and exposure to hazards can increase.
• Mature, slowly growing cities often have to deal with ageing infrastructure and expensive retrofitting. Service needs also change as their populations age.
• Shrinking cities may be left with vacant buildings and oversized networks. A reduced tax base makes maintenance harder. Lower demand can open up opportunities to reuse land, but it doesn't automatically produce sustainability.

These differences don't simply divide richer countries from poorer ones. Cities in the same country can follow different paths. Even prosperous cities can have severe housing shortages or unequal access to services.

Challenges at different spatial scales

A metropolitan transport network may improve access across a region yet leave one neighbourhood poorly connected. For a small coastal settlement, flooding may pose an existential threat, even though fewer people are exposed than in a megacity. The significance of a challenge depends on its local consequences, not just its global total.

Match strategies to the scale and type of change. Rapid growth may call for major network expansion; where populations are stable or declining, selective renewal and adaptation may be more appropriate.

The same strategy distributes costs and benefits unevenly

Urban strategies affect social groups differently. People differ in their incomes and where they live, as well as in their livelihoods and access to services. Even when a policy benefits the environment overall, some residents may face substantial costs.

Restrictions on car use, for example, may improve air quality and favour public transport users. Yet they can disadvantage workers who travel at times or to places that transit serves poorly. Whether affordable alternatives are provided partly shapes the outcome.

Contrasting perspectives

• Low-income residents and tenants may prioritize secure housing alongside affordable fares and basic services. If environmental improvements raise rents or lead to displacement, residents may see them as a threat.
• Homeowners and developers may value rising property prices and opportunities to invest. They may still disagree over density, planning restrictions and construction costs.
• Businesses and workers may support reliable transport and utilities, yet resist measures that raise operating costs or disrupt access during construction.
• Older people and disabled residents may prioritize public space they can access and services nearby, along with alternatives to digital-only systems.
• Environmental groups may favour lower emissions and reduced resource use, as well as biodiversity protection. They may question strategies that merely transfer impacts elsewhere.

These priorities are possible, not fixed views held by everyone in a group.

Judging priorities for action

Judging trade-offs means asking who pays and who benefits. Where do the effects occur, and how long will benefits take to appear? Flood protection may reduce losses for many years, but it can require substantial spending now. Smart services may improve efficiency while raising concerns about privacy. New parks can improve health and cooling, yet they can also raise nearby housing costs.

Through meaningful participation, planners can discover needs they have overlooked. Making decisions transparent and providing affordable services, alongside measures against displacement, can make sustainability strategies more inclusive. Evaluation should weigh effectiveness and fairness against cost and long-term maintenance, rather than assume that one design is best for every community.

Match the representation to the geographic question

Choose the graphic to suit the question: does the information concern location, movement, quantity, composition or change through time? Include clear titles, units, keys, dates and sources. Distinguish projected information from observations.

Patterns and movements

A choropleth map shades areas according to a numerical variable. Use it to show urban shares or population density, but remember that large shaded regions can hide major internal differences. To compare the total populations of individual cities, a proportional-symbol map is better.

Trends, composition and relationships

Grouped bars compare categories side by side. To show how components make up a total, use stacked bars; 100% stacked bars compare proportions rather than absolute sizes. Population pyramids reveal age and sex structure and help identify ageing or a concentration of working-age adults. A scatter graph shows the relationship between two variables. An association alone, though, does not establish causation.

Avoiding misleading comparisons

Compare urban share with urban share, and population totals with population totals. Keep settlement definitions consistent where possible: a central municipality and an entire metropolitan area are not equivalent units. A boundary change can produce an apparent population increase even without migration or natural increase.

The way you draw a graph affects how readers interpret it. Unequal time intervals, omitted units or a shortened vertical axis can exaggerate differences. Choose a representation that preserves the scale of change. It should make spatial or temporal contrasts visible without implying more certainty than the information supports.