Contemporary Urban Environments 10

Cities impact on the environment at a local scale.

Urbanisation also causes loss of open space in and around cities, resulting in loss of habitats and biodiversity.

At a global scale, cities increase demand for resources, such as food, water and energy. Cities are home to around half the world's population, but account for about three-quarters of resource  use. This is putting pressure on finite  resources, leading to food, water and energy insecurity.

Cities are also responsible for about 60% of greenhouse gas emissions, which contribute to climate change.

An individual's ecological footprint is the amount of land that is needed to produce everything they consume, e.g. food, water and fuel, and to absorb their waste. The ecological footprint of an area combines the footprints of its residents.

The ecological footprint of a city depends on a range of factors, including:

• Wealth - e.g. consumption and waste production is higher in cities in richer countries.
• Size of city - e.g. compact cities are easier to travel around on foot or by bike, so they produce less pollution.
• Quality of public transport - efficient public transport systems decrease car use, and therefore reduce pollution.

To be sustainable, a city must meet the needs of people today without preventing future generations from meeting their needs.

There are different dimensions to sustainability - how sustainable a city is depends on its natural, physical, social and economic characteristics. Sustainable cities have a range of features:

Natural:

• Natural sustainability is about how the environment, resources and waste are managed.
• Cities with a high level of natural sustainability rely on renewable energy sources. They produce relatively little waste, and reuse or reycle the waste they produce.
• Cities where people walk, cycle and use public transport a lot produce less pollution, so they are more sustainable.

Physical:

• Physical sustainability is about how well a city is able to support the people living there.
• To be sustainable, a city must provide enough resources to support the population and let them be productive, e.g. have jobs.
• Features of physically sustainable cities include plentiful high quality…