IB Environmental systems and societies 8.2A Urban Systems Notes

Urban Systems: A City Runs on the Same Storages and Flows as Any Ecosystem

An urban ecosystem works like any other ecosystem, but human activity dominates its biotic and abiotic components.

Components of Urban Ecosystems

1. Biotic components (living organisms)
   1. Plants: trees, shrubs, and grass supply oxygen, cut pollution, and cool the air.
   2. Animals: birds, insects, rodents, pets, and urban wildlife such as foxes and raccoons.
   3. Humans: the dominant species, shaping and modifying the whole environment.
   4. Microorganisms: bacteria and fungi that decompose organic matter and recycle nutrients.
2. Abiotic components (non-living factors)
   1. Soil: often altered by construction, pollution, and erosion, which affects plant growth.
   2. Water: rivers, lakes, and reservoirs plus artificial sources like fountains and drains.
   3. Air: pollution from vehicles and industry lowers air quality and harms health.
   4. Climate: cities run hotter because of the urban heat island effect, where concrete and asphalt absorb and hold heat.
   5. Topography: elevation and slope shape drainage, vegetation, and planning.

Urban Areas: Characteristics and Classification

Characteristics of Urban Areas

Urban areas serve residential, cultural, commercial, industrial, and social functions.

1. High population density: far more people per square kilometre than rural areas.
2. Dense infrastructure: roads, buildings, transport networks, and utilities such as power and water.
3. Economic activity: hubs for trade, industry, business, and jobs.
4. Technological development: strong access to modern amenities, healthcare, and communication.
5. Cultural and social hubs: diverse communities, entertainment, and educational institutions.

Urban vs Rural Areas

Classification of Urban Areas

1. Cities: large centres with major population, infrastructure, and governance.
2. Towns: smaller than cities, but still with sizeable infrastructure and economic activity.
3. Suburbs: lower-density residential areas on the outskirts of a city.

The City as a System: Inputs, Processes, Stores, and Outputs

A city is a complex system in which buildings, infrastructure, natural elements, and people interact through storages and flows.

A storage is a stock that holds matter or energy, while a flow is a process that moves it into, through, or out of the system.

Components of an Urban System

Reading the Systems Diagram

A systems diagram tracks the inputs, processes, stores, and outputs of a city.

1. Inputs (flows into the system)
   1. Natural resources such as water, energy, and raw materials.
   2. Human resources such as labour, governance, and education.
   3. Goods and services such as food, products, and transport.
2. Processes (transfers and transformations within the system)
   1. Transfers move matter or energy without changing its form, such as transport moving goods across the city.
   2. Transformations change its form, such as fuel burned into energy and waste.
   3. Infrastructure development and industrial activity.
   4. Waste generation and management.
   5. Social and cultural activities.
3. Stores (where resources and components build up)
   1. Buildings and infrastructure such as roads, bridges, and homes.
   2. Water reservoirs and storage tanks before distribution.
   3. The human population living in the city.
   4. Energy stores such as batteries, fuel reserves, and power plants.
   5. Waste stores such as landfills and recycling centres.
4. Outputs (flows out of the system)
   1. Waste and pollution such as emissions, sewage, and solid waste.
   2. Products and services such as electricity, water, education, and healthcare.
   3. Urban change such as new buildings and improved transport.
5. Feedback
   1. Outputs can loop back as inputs, so growth in population drives more building, which in turn draws in more people.