8.2 URBAN SYSTEMS & URBAN PLANNING

📌 Definitions Table

Term	Definition (Exam-Ready, 2 Marks)
Urban Heat Islands	Urban areas that experience higher temperatures than surrounding rural areas due to human activity and heat-absorbing surfaces.
Horticulture	The cultivation of fruits, vegetables, and ornamental plants, often on a smaller scale and with intensive techniques.
City Farms	Community-managed urban spaces where crops and animals are raised to promote local food production and environmental education.

• 🧠 Exam Tips:
  
  Link urban heat islands to albedo, impervious surfaces, and climate adaptation in extended responses.
  
  Use examples (e.g., rooftop gardens or urban farms) when asked for application or solutions.

📌 Urban Areas

an urban area is a built-up environment with:

A high population density

A large concentration of buildings and man-made infrastructure

Urban areas serve as centres for residential, cultural, economic, trade and social activities

Cities, towns and suburbs are examples of urban areas

Urban areas contrast with rural areas

Rural areas have:

Lower population densities

More dispersed settlements, often focused on agriculture and natural landscapes

For example, London, UK, is a large urban area with dense population, infrastructure and cultural hubs whereas the Lake District in the UK is a rural area with scattered villages and a focus on agriculture and tourism

Urban ecosystems

• Urban ecosystems are unique environments found within cities and towns
  • They occur where human activities interact with natural elements like plants, animals and climate
• These ecosystems have both biotic components (living organisms like plants, animals and humans) and abiotic components (non-living parts like soil, water, air and urban infrastructure).

Types of urban ecosystems

• Residential gardens:
  • Gardens found in residential areas are important urban ecosystems, providing habitats for plants, birds, insects and small mammals
  • These areas also help to improve air quality and reduce the effects of urban heat islands
• Industrial sites:
  • Industrial areas include factories, warehouses and other business operations
  • These areas may cause pollution, but some are now being redeveloped with green spaces to improve the environment
• Inner-city derelict land:
  • Abandoned or derelict land in cities can become important for wildlife and urban regeneration projects
  • These areas often develop biodiversity as nature reclaims the land
• Green areas and open spaces:
  • Urban parks and green spaces are essential ecosystems, offering habitats for animals, improving air quality and providing recreational space for people
• Traffic corridors:
  • Areas alongside roads and railways form their own ecosystems, with hardy plants and animals that can survive in polluted or disturbed environments
  • Urban planners can design green corridors along these routes to help connect different wildlife habitats within cities
• Cemeteries:
  • Cemeteries are often quiet, green spaces within urban areas that support a wide range of plant and animal life
  • They can act as biodiversity hotspots, with trees, grass and other vegetation supporting birds, insects and small mammals
• Waste disposal areas:
  • Landfills and waste treatment plants are part of urban ecosystems
  • Although they can cause pollution, they are also home to certain species of birds, insects and bacteria that thrive in waste environments
• Forests, fields and water bodies:
  • Some urban areas contain patches of forests, fields, lakes or rivers, which provide crucial habitats for wildlife and help with urban temperature regulation

Components of urban ecosystems

Urban infrastructure: buildings, roads, bridges and other structures are integral to urban ecosystems, affecting how people and nature interact

Biotic components:

Plants (trees, shrubs, grass) found in parks, gardens and along streets

Animals such as birds, insects and mammals

Humans, whose activities like construction, gardening and commuting shape the ecosystem

Microorganisms, including bacteria and fungi that break down waste and enrich soil

Abiotic components:

Soil: essential for plant growth in urban parks and gardens

Water: found in rivers, lakes and urban infrastructure like water supply systems

Air: clean air is important for health but urban areas often face challenges with air pollution

Climate: urban areas often create a microclimate, with higher temperatures due to buildings and infrastructure

Urban systems

• An urban system is a network of interconnected elements that work together to support life in a city or town
• Urban systems involve:
  • Buildings
  • Transport
  • Power and energy supply
  • Water supply
  • Sewage systems
  • Plants and animals
  • Humans

Components of urban systems

Buildings and infrastructure

• Buildings form the core of an urban system, providing residential, commercial and industrial spaces
• Infrastructure such as roads, bridges and utilities (electricity, water and waste) connects and supports the functioning of the urban area

Transport

• Urban areas rely on transport systems like roads, railways and buses to move people and goods
• Efficient transport systems are essential to reduce traffic congestion and air pollution
  • For example, London’s Underground is a major part of the city’s urban transport system, helping to reduce road traffic

Power and energy

• Urban systems require energy to power homes, businesses and industries
  • This energy can come from fossil fuels, nuclear power or renewable sources
  • Ensuring a reliable and sustainable energy supply is vital for cities to function properly

Water and sewage

• Water supply systems provide clean water for drinking, washing and other daily needs
• Sewage systems remove and treat wastewater to prevent pollution and maintain hygiene

Microclimate

• Cities create their own microclimates
  • They often become warmer than surrounding rural areas (urban heat island effect)
  • This is due to the high concentration of human activities and infrastructure
• Urban planners consider green spaces and certain building designs and materials to manage urban microclimates

Humans, plants and animals

• Urban systems support human populations, as well as urban wildlife and plants in parks, gardens and green areas
  • These living (biotic) components of urban ecosystems provide recreational spaces and contribute to air quality and biodiversity

Other factors in urban systems

Urban waste and pollution

• Cities generate large amounts of waste and pollution, including solid waste, air pollution and water contamination
  • Managing waste and reducing pollution is critical to maintaining urban efficiency and public health

Urban efficiency

• Urban efficiency refers to how well a city uses its resources, including energy, water and transport systems
  • More efficient urban systems can reduce waste, cut down pollution and improve quality of life for residents

Urban sustainability

• Sustainability is about ensuring that urban systems can meet the needs of the present without harming future generations
  • Sustainable cities focus on reducing their environmental impact by using renewable energy, reducing waste and promoting green spaces
• Urban systems can operate with different types of resource management
  • They might follow either a linear or circular metabolism approach, which affects sustainability and waste management in cities
  • Linear metabolism cities:
    • These are cities that follow a ‘take, use, dispose’ approach
    • Resources (like energy and water) are used once and then discarded as waste
    • This leads to high levels of consumption and pollution
  • Circular metabolism cities:
    • These are cities that focus on recycling, reusing, and reducing waste
    • This approach aims to minimise resource use by creating a closed-loop system where outputs (like waste) are reused as inputs (e.g. recycling materials or generating energy from waste)

❤️ CAS Tip: Participate in an urban greening or pollution-reduction project (e.g., rooftop gardening, street cleanups).

Urban resilience

• Resilience refers to a city’s ability to recover from challenges like natural disasters, climate change oreconomic crises
  • Resilient urban systems have strong infrastructure, emergency services and disaster preparedness plans
  • For example, after Hurricane Katrina (2005), the city of New Orleans, USA, improved its flood defences and urban infrastructure to increase resilience against future disasters

Urban system flow diagram

• An urban system can be represented using a systems flow diagram by showing how resources (inputs) move through the city, are used, and generate outputs like waste and pollution

1. Inputs: the resources a city needs to function
   • Examples: energy (electricity, fuel), water, food, goods (materials for buildings and infrastructure), and labour (human workforce)
2. Processes: how the city uses these inputs in its daily operations
   • Examples: buildings, transport systems, services (healthcare, education), and infrastructure(roads, power plants, water supply)
3. Outputs: the results of urban processes, often in the form of waste
   • Examples: solid domestic waste (rubbish, recycling), pollution (air and water), and sewage
4. Feedback: information or actions that help the system improve in efficiency, sustainability, and resilience
   • Examples: urban planning decisions (like building more green spaces), implementing renewable energy, and waste management initiatives

📌 Urbanisation

• Urbanisation is the process where a growing proportion of a country’s population moves from rural areas (countryside) to urban areas (cities and towns)
  • This shift results in land becoming more built-up, with infrastructure, housing, and industrialisation dominating the urban landscape
  • As urbanisation occurs, cities:
    • Expand
    • Develop more dense populations
    • Experience more continuous human activity
• According to the World Bank, 56% (4.4 billion) of the world’s population now live in towns and cities

Rural–urban migration

• Rural-urban migration is a major factor driving urbanisation
  • It is the movement of people from the countryside to cities in search of:
    • Better living conditions
    • Job opportunities
    • Safety
• This migration causes the urban population to grow, often at the expense of the rural population
  • For example, in China, rural-urban migration has led to massive city growth, with people moving from farming regions to cities like Shenzhen and Beijing in search of jobs in factories or offices
• Rural-urban migration is mostly internal migration (within a country)

Urbanisation pathway

• Countries become more urban as they develop economically
• This transition from LICs to HICs can be shown as a pathway over time 
• The pace through the stages slows and flattens or will decline as counter urbanisation gains speed

Push and pull factors of rural–urban migration

• Push factors are the reasons people leave rural areas
• These include:
  • Poverty: lack of jobs and low wages in rural areas
  • Poor living conditions: limited access to services like healthcare, education, and clean water
  • Natural disasters: droughts, floods, or other environmental challenges that make farming difficult

• Pull factors are the attractions of urban areas that draw people to move there
• These include:
  • Job opportunities: cities often offer more and better-paying jobs, especially in industries, services, and trade
  • Improved living conditions: access to better healthcare, education, and housing in cities
  • Social and cultural opportunities: cities provide more entertainment, cultural events, and lifestyle choices

Forced and voluntary migration

• Voluntary migration:
  • When people choose to move to cities for better opportunities or living conditions
• Forced migration:
  • When people are pushed into cities due to circumstances like war, famine, or natural disasters
  • For example, refugees fleeing conflict in Syria and moving to urban areas in nearby countries such as Turkey and Jordan

De-urbanisation trends

• Deurbanisation refers to the reverse process where people move out of cities and back to rural or suburban areas
• This can happen due to:
  • Overcrowding: cities becoming too congested, leading to higher costs of living and poorer living conditions
  • Improved rural opportunities: development in rural areas offering better services, jobs, and living conditions
  • Technological changes: with the rise of remote working, people can live in rural areas while working for urban companies

🔍 TOK Tip: Can urban planning solve social inequalities?

📌 Urban Expansion

• Suburbanisation is the process where people move from the dense central parts of cities (urban areas) to the less dense, peripheral areas (suburbs)
  • It involves the expansion of cities into nearby rural or undeveloped areas, creating lower-density residential areas
  • People often move to the suburbs in search of larger homes, green spaces, and better living conditions away from the congested city centre

What is urban sprawl?

• Urban sprawl refers to the uncontrolled expansion of urban areas into surrounding rural land, creating spread-out developments
  • Urban sprawl is closely related to suburbanisation, as lower-density housing and commercial developments require more land, stretching the boundaries of the city
  • Sprawl often leads to longer commutes, greater car dependency, and increased demand for infrastructure such as roads and services

Causes of suburbanisation

1. Desire for more space:
   • People move to the suburbs for larger homes and gardens
   • Suburban areas often have more green spaces and parks than city centres
2. Improved transport links:
   • Advances in public transport and the widespread use of cars have made commuting from the suburbs to city centres easier
   • Suburban residents can travel to the city for work, shopping, and leisure
3. Perception of better quality of life:
   • Suburbs are often seen as safer, quieter, and better for raising families compared to crowded city centres
   • Suburban areas may offer better schools and lower crime rates
4. Rising urban costs:
   • High costs of housing and living expenses in city centres push people to move to the more affordable suburbs
5. Traffic congestion and overcrowding in city centres:
   • City centres are often very busy with people and congested with traffic, making commuting and living in the urban core more difficult

Environmental impacts of urban expansion

Loss of agricultural land and natural ecosystems

• Loss of farmland:
  • As cities expand, they often take over land previously used for agriculture
  • This reduces the amount of land available for growing food
  • For example, in Beijing, China, rapid urbanisation has consumed large areas of farmland, leading to concerns about food security
• Deforestation:
  • Urban expansion can lead to the clearing of forests to make way for housing, roads, and businesses
  • This destroys natural habitats and reduces biodiversity
    • For example, the growth of São Paulo, Brazil, has resulted in the destruction of parts of the Amazon rainforest
• Loss of wetlands and ecosystems:
  • Expanding urban areas often fill in wetlands, rivers, and lakes, reducing habitats for wildlife and affecting water systems
    • For example, in Florida, USA, urban sprawl has reduced the size of the Everglades, an important wetland ecosystem

Changes to water quality and river flows

• Water pollution:
  • Increased construction and industrial activities near cities can cause pollution to rivers, lakes, and groundwater
  • Chemicals from factories, waste from homes, and run-off from roads can contaminate water supplies
    • For example, the Ganges River in India suffers from severe pollution due to urban growth and industrial waste from several major cities
• Altered river flows:
  • Expanding cities often build dams, divert rivers, or drain wetlands, which changes the natural flow of water
  • This can lead to flooding or drought in nearby areas
    • For example, in Las Vegas, USA, the city’s rapid growth has strained the Colorado River, leading to water shortages and environmental issues

Air pollution

• Increased traffic and industry:
  • As cities grow, they generate more air pollution from cars, trucks, and factories
  • This increases levels of harmful gases like carbon dioxide and nitrogen oxides, contributing to climate change and health problems
    • For example, Mexico City is known for having high levels of smog and poor air quality due to urban expansion and traffic congestion
• Heat islands:
  • Urban expansion often creates urban heat islands
  • This is where cities become significantly warmer than surrounding rural areas
  • This happens because buildings, roads, and other urban surfaces absorb and retain more heat than natural landscapes like forests or grasslands
  • Air conditioners, vehicles, and industrial activities release additional heat into the environment

Loss of biodiversity

• Habitat destruction:
  • Urban expansion can destroy the natural habitats of plants and animals, leading to a reduction in biodiversity
  • This puts species at risk of extinction

📌 Urban Planning

• Urban planning is the process of designing how land and buildings in a city are used to meet the needs of the population
  • It focuses on the best way to organise urban space to meet the physical, environmental, commercial, industrial, and social needs of all residents
• Effective urban planning ensures that cities grow in an organised and efficient way
  • This is to prevent issues like overcrowding, pollution, and inadequate infrastructure
• Modern urban planning aims to create sustainable urban systems that balance the needs of the population with environmental protection
  • In this context, sustainability means designing cities so they work well and fairly for people today, while also making sure they can meet the needs of future generations

Factors in sustainable urban planning

1. Quality and affordable housing:
   • Ensuring housing is available and affordable to all income levels is key for sustainable development
2. Integrated public transport systems:
   • A well-connected, reliable, and environmentally-friendly public transport system reduces the need for cars and lowers pollution
     • For example, Copenhagen, Denmark, has reduced car use by focusing on bicycle lanes and public transport
3. Green spaces:
   • Parks, forests, and other green areas improve air quality, provide recreational spaces, and contribute to the well-being of residents
     • For example, Brasilia, the capital of Brazil, was designed with a very large linear park running down its centre, promoting a balance between urban development and nature
4. Security and safety:
   • Creating safe neighbourhoods with reduced crime rates and effective emergency services
   • Good lighting, surveillance, and safe public spaces contribute to a secure urban environment
5. Education and employment:
   • Providing access to schools, universities, and job opportunities is essential for sustainable cities
   • Urban systems must plan for education and employment to keep the population economically active
6. Renewable energy and resources:
   • Sustainable cities aim to use renewable energy sources like solar or wind power to reduce reliance on fossil fuels
     • For example, San Francisco, USA, has invested in electric vehicle (EV) charging stations to encourage the use of cleaner energy for transportation
7. Reuse and recycling of waste:
   • Sustainable cities focus on reducing waste, reusing materials, and promoting recycling to minimise environmental impact
     • For example, in Singapore, waste-to-energy plants help recycle waste while producing energy for the city
8. Energy efficiency:
   • Buildings in sustainable cities are designed to use energy efficiently, reducing waste and lowering energy costs
   • Green buildings incorporate insulation, solar panels, and other technologies to minimise energy consumption
9. Water conservation:
   • Cities must plan for efficient water use and ensure water conservation practices.
   • For example, Dubai uses grey water to irrigate its green spaces, conserving fresh water resources
10. Community involvement:
    • Successful urban planning involves the local community in decision-making processes
    • This ensures that the needs and ideas of residents are considered

What is ecological urban planning?

• Ecological urban planning treats the city as an ecosystem
  • This type of urban planning considers the interactions between living (biotic) and non-living (abiotic) components
  • It focuses on:
    • Creating balance between urban development and the natural environment
    • Ensuring cities are sustainable, resilient, and healthy for both humans and wildlife

🔍 TOK Tip: How do political ideologies shape urban development?

Key components of ecological urban planning

Urban ecology

• Urban ecology integrates green spaces and natural habitats into city design
• This includes parks, allotments, ponds, canals, and other areas that provide habitats for wildlife and improve air quality

Urban farming

• Urban farming refers to growing food within cities
  • This is often done in unused or repurposed spaces
• This Includes activities like beekeeping, horticulture, aquaculture, and city farms
  • For example, New York City has community gardens and rooftop farms that supply fresh produce to local residents

Biophilic design

• Biophilic design brings nature into the built environment by incorporating natural elements into architecture
• This includes living green walls, rooftop gardens, water features, and the use of natural light
  • For example, the Bosco Verticale (meaning vertical forest) in Milan, Italy, is a complex of two residential skyscrapers covered in trees and plants, improving air quality and biodiversity

Resilience planning

• Resilience planning focuses on designing cities to withstand and adapt to environmental challenges like climate change
• This may involve:
  • Vertical farming to produce food in limited urban spaces
  • Buildings on stilts to protect from flooding in flood-prone areas
  • In flood-prone areas, such as the Netherlands, some homes are built to float on water, adjusting to rising and falling water levels
  • Using natural elements like green roofs and permeable pavements to manage stormwater and reduce flooding

Regenerative architecture

• Regenerative architecture aims to not only reduce environmental harm but actively improve the environment
  • Building skins that clean the air:
    • Some buildings are designed with special materials or coatings on their exterior walls (known as building skins)
    • These filter and remove pollutants (e.g. nitrogen oxides) from the air, improving air quality around the building
  • Renewable energy sources:
    • Many regenerative buildings use solar panels, wind turbines, or bio-digesters to generate more energy than they consume
    • They are then able to contribute clean energy back to the energy grid
  • Bio-digesters:
    • These systems use organic waste (like food or agricultural waste) to produce biogas
    • This can be used as a renewable energy source for heating or electricity
    • They also create natural fertiliser as a by-product
  • Rainwater capture systems:
    • Buildings can collect rainwater to be reused for non-drinking purposes, e.g. irrigation or flushing toilets
    • This reduces the demand on local water supplies