L8: Global Change and Urbanisation

Urbanisation

Process in which an increasing proportion of a society lives in cities and the suburbs

Causes of urbanisation

• Employment opportunities

• Modernisation

• Industrialisation

• Social benefits

Global urban expansion rate

• India → x3 mil

• Sydney → Expanding westward toward Blue Mountains

• Seine river → Expansion of city into rural areas

• Mexico → Fastest growing megalopolis

• Beijing → Explosive growth since economic reforms (x2 EU)

Reasons for China’s urban population growth

• Rapid economic growth (Massive industrialisation)

• Rural to urban migration

• Local government desire to grow

• Gov policy to shift population from agriculture to urban manufacturing and services

Relation between urban governance and funding

Governance and funding of Chinese cities is v important

• All urban land is owned by the state

• Source of urban revenue is land sales

Relationship between cities and climate change

Cities = Contributor + Victim

• Contribute 70% of GHG emissions

• Vulnerable to effects of climate change

Cities’ contribution to climate change

• Electricity generation

• Urban transport

• Building + construction

• Urban expansion

• Waste

What do the impacts and threats between cities depend on?

• Geographic location

• Specific geographic features

• Vulnerable populations

• Sensitivity

Flooding

• Sea level rise

• Increased rainfall

• Affects coastal cities

Urban heat island

• Occurs when a city experiences much warmer temperatures than nearby rural areas

• Diurnal behaviour: Cities often experience stronger urban heat island effects at night

Surface Heat Islands

Form because urban surfaces absorb and emit heat to a greater extent than natural surfaces

Atmospheric Heat Islands

Form because of warmer air in urban areas compared to cooler air in outlying areas

How do urban heat islands form (7)?

• Weather + Geography

• Reduced natural landscapes

• Less water cycling

• Urban material properties

• Absorption of solar radiation

• Urban geometry

• Heat generated from human activities

Weather + Geography

• Calm weather conditions result in more severe heat islands

• Geographic features can also impact heat island effect

Reduced natural landscapes

Less evapotranspiration from plants to cool the air

Urban material properties

• Dark impervious surfaces absorb + retain heat

• Solar reflective roofs, walls, and pavements lower surrounding air temperature

Absorption of solar radiation

Low albedo

Urban geometry

Urban canyons trap heat and pollutants

Heat generated from human activities

Waste heat from vehicles + aircon warms air

Effects of UHI

• Increased energy consumption leads to increased expenditure

• Elevated emissions of air pollutants and greenhouse gases

• Urban haze

Methods for reducing urban heat islands

• High albedo roofing materials (light colored roofs)

• Green roofs

• Solar panels on roof

Climate change action strategies

• Climate change mitigation → Reduce human-generated GHG emission

• Climate change adaptation

Climate change adaptation

• Process through which communities prepare to cope with potential effects of climate change

• Adaptive capacity

Mitigation strategies

• Reduced motorised transport dependency

• Reducing fossil fuel dependency

• Improving waste management