Urban systems and urban planning

· Urban ecosystems are ecosystems within urban areas; they include biotic components (humans, plants, animals, microorganisms) and abiotic components (soil, water, air, climate, topography, buildings and infrastructure).
· Urban area = built-up area with high population density, buildings and infrastructure; includes cities, towns and suburbs.
· Urban system = interconnected buildings, microclimate, transport, goods and services, energy, water supply, sewage, humans, plants and animals.
· Treat cities as open systems: they need inputs and produce outputs, so they can be analysed using systems diagrams.
· Exam focus: explain how urban systems affect waste/pollution, efficiency, sustainability and resilience.

Urban system inputs and outputs

· Inputs may include food, water, energy, raw materials, manufactured goods, people, money and information.
· Outputs may include solid waste, sewage, air pollutants, water pollutants, waste heat, greenhouse gases, noise and exported goods/services.
· Transfers in cities include movement of people, water, waste, goods and energy.
· Transformations include fuel combustion, waste treatment, food processing, construction, and conversion of land into built infrastructure.
· High-performing exam answers should link urban flows to resource consumption, pollution, ecological footprint and sustainability.

Urbanization, suburbanization and sprawl

· Urbanization = population shift from rural to urban areas and increasing conversion of land into built-up, industrialized, dense settlement.
· Rural–urban migration is often driven by push factors (poverty, unemployment, conflict, environmental degradation) and pull factors (jobs, education, healthcare, services, perceived opportunities).
· Migration may be forced or voluntary; most rural–urban migration is internal migration within a country.
· Suburbanization = movement from dense central urban areas to lower-density peripheral areas.
· Urban sprawl = low-density outward growth; it usually increases land take, car dependency, infrastructure costs and habitat loss.
· Deurbanization may occur where people move out of urban areas due to high living costs, congestion, pollution, remote work or declining urban industries.

Environmental impacts of urban and suburban expansion

· Expansion of urban systems can cause loss of agricultural land, deforestation, habitat fragmentation and loss of natural ecosystems.
· More impermeable surfaces increase surface run-off, alter river flows, reduce infiltration and can increase flood risk.
· Urban systems can reduce water quality through sewage, urban run-off, industrial effluent, road pollutants and litter.
· Air pollution increases when transport, construction and energy systems rely on fossil fuels.
· Urban growth can increase waste production, greenhouse gas emissions, noise pollution and the urban heat island effect.
· Strong evaluation: urbanization can also improve efficiency if planned well through compact design, public transport, shared infrastructure and green technology.

Urban planning and sustainable urban systems

· Urban planning decides the best use of land and buildings to meet community needs.
· Urban planning should consider physical, domestic, environmental, commercial, industrial, financial and health needs of stakeholders.
· Sustainable urban planning aims to improve environmental quality, social equity and economic viability.
· Key features include quality and affordable housing, integrated public transport, green spaces, security, education, employment, renewable resources, reuse and recycling, energy efficiency, community involvement and green buildings.
· Case examples to know: Cerdà Plan in Barcelona, Haussmann Plan for Paris, Brasilia, Forest City in Malaysia, Copenhagen car-use reduction, San Francisco EV charging, Dubai grey-water irrigation.
· Exam skill: use maps to interpret how a city has developed over time and link changes to sustainability.

The Cerdà Plan is a useful case study for planned urban expansion. Students can use it to discuss grid layouts, public health, transport, equality of access and long-term urban development. Source

Ecological urban planning

· Ecological urban planning treats the urban system as an ecosystem, focusing on relationships between biotic and abiotic components.
· It is more holistic than traditional planning because it considers flows, feedbacks, biodiversity, water, energy, waste and resilience together.
· Urban ecology examples: green spaces, wildlife habitats, allotments, parks, canals and ponds.
· Urban farming examples: beekeeping, horticulture, aquaculture, city farms and vertical farming.
· Biophilic design examples: living green walls, green roofs, water features and natural light.
· Resilience planning examples: vertical farming, buildings on stilts in flood-prone areas, fail-safe grids and climate-adapted infrastructure.
· Regenerative architecture examples: building skins that scrub air, systems that capture rainwater, and buildings that generate/export renewable energy.

This diagram shows how green roofs combine built infrastructure with living vegetation. It supports links between biophilic design, stormwater management, biodiversity, insulation and reduction of urban heat islands. Source

How sustainable urban planning improves resilience

· Green spaces improve biodiversity, reduce urban heat, increase infiltration, improve mental health and provide recreation.
· Integrated public transport reduces car dependency, fossil fuel combustion, air pollution, traffic congestion and GHG emissions.
· Energy-efficient buildings reduce demand for heating/cooling and lower carbon footprints.
· Water-sensitive design uses rainwater harvesting, grey-water recycling, permeable surfaces and restored wetlands to reduce water stress and flooding.
· Waste systems based on reuse, repair, recycling and composting reduce landfill and resource extraction.
· Community involvement improves acceptance, equity and long-term success of urban plans.
· Strong evaluation: sustainability strategies can fail if they cause green gentrification, exclude low-income groups or shift environmental costs elsewhere.

Exam evaluation phrases

· “Urban areas function as open systems because…” they import resources and export waste, pollution and services.
· “A sustainable city reduces inputs and harmful outputs by…” improving efficiency, recycling resources and using renewable energy.
· “Urban sprawl is less sustainable because…” it increases land take, car dependency, habitat loss and infrastructure demand.
· “Ecological urban planning is holistic because…” it treats social, built and natural components as interconnected.
· “This strategy improves resilience by…” reducing vulnerability to flooding, heat, resource shortages or system failure.
· “However, environmental justice must be considered because…” benefits such as green space may not be equally accessible.

Common mistakes to avoid

· Do not describe cities only as “built environments”; they also contain urban ecosystems with living and non-living components.
· Do not say urbanization is always negative; evaluate both benefits and costs.
· Do not confuse urbanization with suburbanization: one is rural-to-urban shift, the other is movement to lower-density city edges.
· Do not list sustainable strategies without explaining how they reduce inputs, reduce outputs or improve resilience.
· Do not ignore environmental justice: sustainable planning must consider who gains and who loses.