Date post: | 06-Apr-2018 |
Category: |
Documents |
Upload: | peter-greener |
View: | 218 times |
Download: | 0 times |
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 1/21
Cities As Systems
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 2/21
What is a System?
• A system is a simplified way of looking at how
things work.
• Systems generally include factors (inputs),
processes (throughputs) and results (outputs).
• The systems approach can be applied to many
aspects of geography, including cities.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 3/21
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 4/21
Cities as systems: Open linear systems
The Unsustainable City
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 5/21
Inputs
• The inputs may be made up of:
- people, whether daily commuters or more
permanent migrants and immigrants,
- goods such as bricks, bread, furniture and
computer microchips
- services such as water and electricity.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 6/21
Outputs
• Outputs like:
- waste water and refuse,
- outgoing commuters and migrants- ‘unseen' exports like air pollution.
• Where great amounts of products are
exported without much recycling, this type of system is called an open system.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 7/21
Why Are These Systems
Unsustainable?
• Such a system may be thought of as
unsustainable in the long term because of the
escalating demands for resources from an
ever-widening area, creating a widening
ecological footprint.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 8/21
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 9/21
Example: London
• London has experienced great changes in itspopulation which in turn has had implications forthe land area occupied and needs for inputs andoutputs – the basis for any system.
• Sustainability depends on the nature and balanceof the system.
• If the system grows in total numbers, it will
require more inputs and inevitably produce moreoutputs.
• If the system reduces or increases in numbers of working age group, other issues will ensue.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 10/21
Example: London
•London's total footprint, following Rees's definition,extends to 20 million hectares: around 125 times itssurface area of 159,000 hectares.
• With approximately 12% of the UKs population,7,000,000 people live in London, occupying a surface
area of 158,000 hectares.• The area required for food production at 0.2 hectares
per person is 8,400,000 hectares.
• The forest area required by London for wood products
is 768,000 hectares.• The land area that would be required for carbon
sequestration (fuel production) at 1.5 hectares perperson is 10,500,000 hectares.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 11/21
• The total London footprint is 19,700,000hectares: 125 times London's surface area.London therefore requires the equivalent of Britain's entire productive land.
• In reality, with its increasingly sophisticated
consumer tastes aided by rapid transporttechnology, this means London is increasing itsimpact on remoter areas: such as obtainingmangoes from Brazil, teak furniture from
Malaysia, copper from Zambia … not to mentionour appetite for increasingly far flung holidaydestinations…
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 12/21
Conclusion
• Large cities are often considered to be
unsustainable systems because they consume
large amounts of resources and produce large
amounts of waste.
• Sustainable urban development aims to meet
the needs of the present generation without
compromising the needs of future generations
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 13/21
• Traditional settlements were delineated and
structured by transport and production
systems based on human or animal power
• A major effect of fossil fuel-based technology
has been that the high density of traditional
cities has given way to urban sprawl creating
an increasing ecological footprint.
Reasons for the Problems
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 14/21
• As cities draw resources from increasing
distances, they also accumulate large amounts
of inert and toxic materials within themselves
– that is to say, pollution.
• Waste gases and water expand the negative
impact of cities at a regional and increasingly
global scales.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 15/21
Cities as sustainable systems: Circular
metabolism
• In nature, a circular metabolism is developed
whereby every input is also able to renew and
sustain the living environment by recycling the
outputs. In the past medieval cities had
something approaching this relationship, with
the following closely linked nearby: market
gardens, orchards, arable and grazing land,local water supply, forest products and so on.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 16/21
Cities as systems: Circular Metabolism
The Sustainable City
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 17/21
Looking at the Past to look at the
Future
• Indeed, until the recent and rapid industrially led
growth of the late twentieth century, many
Chinese cities were largely self-sufficient in food.
• They were unique among the world in having
highly developed low technology systems of using
human waste as fertiliser for local farms.
•It must be stressed that any city has an ecologicalfootprint – the question is to what degree?
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 18/21
•
Cities in less economically developedcountries such as India often have a higher ‘re-
use' system than do those in more
economically developed countries.
• In the USA and UK, ‘disposable culture' and
‘built-in obsolescence' permeate society.
• Modern cities have broken the close links with
the local biosphere.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 19/21
The Key to Sustainability
• In order for cities to become more sustainable
they must change the linear metabolism to a
more circular metabolism, creating a self-
regulating sustainable relationship with the
biosphere.
• To do this they will need to become more
compact cities.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 20/21
Compact Cities
• Compact cities minimize the amount of
distance travelled, use less space, require less
infrastructure (pipes, cable, roads, etc.), are
easier to a provide public transport network
for, and reduce urban sprawl.
8/2/2019 Cities as Systems
http://slidepdf.com/reader/full/cities-as-systems 21/21
Warning!!
• However if the compact city covers too large
an area it becomes congested, overcrowded,
overpriced and polluted.
• It becomes unsustainable.