Describe what is meant by a “sustainable city”.

Explain three ways in which human activities can modify the microclimate of an urban area.

Examine reasons why cities in some parts of the world have higher rates of population growth than others.

Answers could include the following elements:

A city that is designed to protect quality of life for its future generations [1 mark].

Award 3 marks for three of the following elements:

• city designed to minimize impact on environment
• inputs of energy, water, and other resources are minimized
• outputs (waste, air and water pollution) are minimized (possibly by recycling)
• effective transport infrastructure minimizes outputs
• smallest possible urban ecological footprint
• any other valid suggestion.

Microclimate can describe temperatures, wind speed, humidity, air quality and local rainfall regimes.

Answers could include the following:

• increased temperatures (including urban heat island effect) because of reduced albedo, direct heating by buildings, air conditioning etc.
• changes in wind speed and air flow because of buildings and street patterns
• changes in rainfall because of higher temperatures; increased amount of particulate pollution provide rainfall nuclei; greater convectional updraughts
• greater levels of air pollution (photochemical smog, particulates, NOX etc.)
• greater number of sources, for example, exhausts.

Award 1 mark for each basic modification explained and 1 mark for any extension or good example.

Maximum 3 marks if only one aspect of microclimate (for example, urban heat island) is explained but with three causes given.

Good answers are likely to focus on migration and natural increase also. Variations in the relative strength of urban pull factors and rural push factors should be discussed. Economic, cultural and political factors may feature in the discussion as influences of both migration and rates of increase.

Counter-urbanization and low birth rates are a cause of slower growth or even a decline in population in many cities in MEDCs.

Responses that focus simply on urban growth in one area should be limited to band D. Expect the inclusion of both migration and natural increase to access bands E/F.

While examples are not a specific requirement of the question, those answers that provide supporting examples are likely to access the higher markbands.

Marks should be allocated according to the markbands.

Sustainability seems to be well understood and most candidates gave a good response – many referred to the Roger's model and many provided annotated diagrams to illustrate it.

Surprisingly, overall, this was done quite poorly. Many referred to the greenhouse effect and there was considerable confusion over the causes of the urban heat island.

Some answers were excellent but many took an inappropriate scale (national population growth rather than urban) or did not consider natural increase as well as migration. The use of supporting examples made it easier for candidates to access higher markbands.