Notes on Urban Systems and Sustainability

Urban Systems and Sustainability

Urban Areas and Ecosystems

• Urban areas contain urban ecosystems, characterized by high population density, buildings, and infrastructure.
• An urban area functions as a system with interconnected components.
• Urbanization involves the movement of population from rural to urban areas.
• Suburbanization is the movement from densely populated urban centers to less dense peripheral areas.
• The expansion of urban and suburban systems leads to environmental changes.
• Urban planning aims to optimize land and building utilization, often considering sustainability.
• Ecological urban planning is a holistic approach that views the urban system as an ecosystem, considering biotic and abiotic relationships.

Ecological Urban Planning Principles

• Ecological urban planning follows principles of:
  • Urban compactness
  • Mixed land use
  • Social mix
• Societies are developing systems that address urban sustainability using models like a circular economy or doughnut economics.
• Green architecture minimizes construction's harmful effects on health and the environment by using environmentally friendly materials and practices.

Urban System Components

• Urban System: Interconnected system of buildings, microclimate, transport, goods/services, power/energy, water/sewage, humans, plants, and animals.
• Urban Ecosystems: Communities of organisms interacting with their abiotic environment within an urban area (e.g., forests, fields, water bodies).
• Urban Area: Developed area with high population density, buildings, and infrastructure.

Urban System: Inputs, Processes, and Outputs

• Food:
  • Inputs: Food
  • Transfers: Food transportation via road and rail networks.
  • Transformations: Processing, digestion, decomposition.
  • Outputs: Food exports, human waste, food waste.
• Water:
  • Inputs: Water
  • Transfers: Wastewater canals, pipelines, rivers, piped into households, businesses, factories, precipitation, surface runoff
  • Transformations: Water treatment for human consumption, wastewater treatment, evaporation, evapotranspiration.
  • Outputs: Polluted water, river water, water vapor
• Fossil Fuels:
  • Inputs: Fossil fuels
  • Transfers: From storage to vehicle or facility via air, road, and rail networks.
  • Transformations: Processing at industrial facilities, combustion in vehicles and electric power generation.
  • Outputs: Plastic waste, goods and services exports, carbon dioxide CO2, sulfur dioxide SO2 and other emissions, heat energy.
• Light:
  • Inputs: Energy radiated from the sun.
  • Transfers: Reflected from light-colored surfaces of roofs and parks.
  • Transformations: Converted into electricity by solar panels, absorbed by dark-colored surfaces and converted to heat, photosynthesis by plants.
  • Outputs: Heat energy, chemical energy (food).

Urban Efficiency

• Definition: Efficiency = ratio of quantifiable inputs to outputs in a system Efficiency = \frac{Outputs}{Inputs}
• Goal: Meet human needs within planetary boundaries while minimizing resource use.
• An efficient city uses minimal energy/resources and maximizes services like light and transport.
• Outputs include physical (waste, heat, pollution, exports) and non-physical/emergent (human wellbeing, ecological health).
• Example: An efficient lightbulb = more light + less energy; same logic applies to cities.
• Challenges:
  • Defining outputs that reflect the full function of a city.
  • Ensuring real efficiency includes positive impacts on both people and the environment.

Urban Resilience

• Definition: Resilience = the ability of urban systems to bounce back from disturbances.
• Characteristics of resilient urban systems:
  • Diverse and abundant resources: Local and distributed sources of energy, food, and water; multiple trade networks.
  • Diverse and abundant services: Education, healthcare, housing, and recreation; social safety nets.
  • Robust and redundant infrastructure: Built for disruption (earthquakes, floods, climate change); adaptable roads, buildings, and transport options.
  • Diverse population and strong social networks: Varied ideas for better planning; strong community ties for mutual support.
  • Strong governance and innovation culture: Creative and inclusive urban solutions; quick mobilization of resources during emergencies.
• Why Urban Resilience?
  • Climate change and social instability require cities to be adaptive and durable.
  • Many cities today are not resilient enough.

Urban Interconnections: Urbanization, Push and Pull Factors

• Urbanization: Movement of population from rural to urban areas.
• Rural to urban migration: Migration due to perceived or real advantages of urban settlements.
• Push factors (from rural areas):
  • Lack of employment and lower wages.
  • Food scarcity due to falling crop yields and lack of access to adequate food resources.
  • Lack of basic services like healthcare and education due to low population densities.
  • Lack of resilience: Poor infrastructure and lack of services reduce the ability to recover after natural disasters.
• Pull factors (to urban areas):
  • Employment and higher wages.
  • Food abundance due to diverse food sources and higher wages.
  • Abundant services due to high demand (high population density).
  • Resilience: Diverse resources and networked populations help urban areas recover after a disaster.

Urban Sprawl

• Definition: Unrestricted spread of low-density urban and suburban development around cities.
• Characteristics:
  • Low-density, single-family dwellings.
  • Vehicle dependency.
  • Lack of connectivity.
  • Undefined edges between rural and urban areas.
• Causes:
  • Lower land values on the rural-urban fringe.
  • Population growth requiring more houses.
  • Increased income enabling people to afford houses.
• Consequences:
  • Increased car use and pollution.
  • Reduction in natural sites.

Suburbanization and De-urbanization

• Suburbanization: Movement of people from central urban areas with dense population to peripheral areas with lower density.
• Reasons:
  • Improvements in transportation.
  • Increase in global trade allowing farmland to be used for housing.
• Results:
  • Uncontrolled urban sprawl.
  • Environmental impacts: reduced biodiversity, lack of green space, changes in land use, increased flooding.
  • To stop urban sprawl, green belts were introduced.
• De-urbanization: Process where people move away from cities to rural areas (e.g., during COVID-19).

Impact of Urbanization on Ecosystems

• Loss of forest and agricultural land: Expansion of urban areas converts land into buildings and infrastructure.
• Changes to natural ecosystems: Urban structures are built over forests, wetlands, and grasslands.
• Water quality and river flows:
  • Increased runoff from paved surfaces leads to water pollution and flooding.
  • Construction near rivers can alter their natural flow.
  • Broken pipes from toilets and kitchen appliances lead to water pollution.
• Energy consumption: Urban areas use large amounts of energy for domestic, service, and industrial activities.
• Air pollution: High vehicle use and industrial activities increase carbon emissions.
• Resource waste: Most food is produced elsewhere; water consumption is high; recycling rates are lower.

Urban Planning Models

• Modern urban planning examples: Brasilia (Brazil), Forest City (Malaysia), Sustainable City (Dubai).

Doughnut Economics Model

• Definition: A holistic framework for sustainable and regenerative urban development.
• Local Social Lens: "How can all the people of this place thrive?"
  • Focuses on human wellbeing and social equity.
  • Cities must provide: affordable housing, clean water, healthy food, quality education, efficient transportation, security, and jobs.
  • Challenges: Marginalized groups often lack access due to poor infrastructure, physical barriers, inadequate services in poor neighborhoods.
• Local Ecological Lens: "How can this place be as generous as the wildland next door?"
  • Emphasizes regenerative urban planning and urban ecology.
  • Provide ecosystem services: air purification, carbon storage, biodiversity, water filtration, cooling and green space access.
  • Urban Planning: Regenerative architecture, solar panels, rainwater harvesting, building skins that clean air, solar panels/wind turbines/biodigesters that export energy
  • Regenerative urban farming: horticulture (e.g., rooftop farms), aquaculture, vertical farming, urban beekeeping.
  • Advantages: production of large amounts of food, income + employment provision, increase food security
  • Biophilic design: increase connections to the natural world through direct/indirect use of nature, space, and place (e.g. living green walls and roofs, water features, natural light)
  • Urban ecology: relationships of living organisms w/ their surroundings in areas w/ high density residential/commercial developments (e.g. green space, habitats for wildlife, allotments, parks, canals, ponds)
  • Resilience planning and vertical farming.
• Global Ecological Lens: "How can this place respect the health of the whole planet?"
  • Cities must operate within planetary boundaries. Reduce environmental impact through lower carbon emissions, minimized energy and material use, and controlled pollution and waste.
  • Strategies: Use renewable energy, promote public transport and biking, support circular economy.
• Global Social Lens: "How can this place respect the wellbeing of all people worldwide?"
  • Urban decisions must consider global social justice through ethical sourcing and global responsibility.
  • Examples: Fair labor practices in global supply chains, support for refugees and migrants, promotion of global social equity through local policies.

Circular Economy Model

• An economic system aimed at eliminating waste and reusing resources by keeping materials in use for as long as possible.
  • Designing buildings for disassembly and reuse.
  • Using recycled or renewable materials.
  • Reducing the overall material footprint and construction waste.

Ecological Urban Planning

• These approaches support meeting human needs within planetary boundaries (Global Ecological Lens).
• Urban Compactness: Dense, organized cities with smaller land footprints.
• Mixed Land Use: Combining residential, commercial, and recreational areas, including green spaces.
• Social Mix: Diverse communities with varied income/social groups; affordable housing across urban areas promotes equity.
• 15 Minute City: All essential services should be within a 15-minute walk, bike, or transit ride.

Green Architecture Techniques & Materials

• Bio-based materials: Wood, bamboo, adobe, straw.
• Circular construction: Reuse/recycle building materials.
• New technologies like 3D printing.
• Solar panels and heat pumps reduce GHGs.
• Indigenous Knowledge Systems: Stilt houses in tropical zones.
• Vernacular Architecture: Local climate/cultural based designs like Barajeel in desert areas.

Environmental Ethics

• Environmental and social justice movements are aligning for shared goals.
• Urban inequality examples: Wealthy areas have good services, green spaces, and healthy food, while poorer areas are near pollution and industrial zones (environmental racism).
• Sustainability must include social justice and equitable distribution.

Environmental Laws

• Definition: International law provides an essential framework for addressing transboundary issues of pollution and resource management.
• Urban projects are assessed through Environmental Impact Assessments (EIA).
• EIA evaluates ecological, social, and economic sustainability and involves stakeholder input.
• Post-development audits and monitoring help track effectiveness.

Environmental Economics

• Tragedy of the commons: A shared resource lacks clear ownership or pricing, leading to overexploitation.
• Atmosphere as a common resource: Shared by all, but no one owns it, leading to undervaluation.
• Example: Air pollution from vehicles affects everyone, but the polluter does not pay the cost.
• Avoiding the Tragedy:
  • Clear rules and responsibilities.
  • Systems for conflict resolution.
  • Cooperation among users.
  • Shared resources can be sustained effectively.