Urbanization: Brief History & Future Outlooks

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Urbanization: Brief History & Future Outlooks

  1. 1. What is urbanization? The migration of people from rural areas and villages into high-population-density “cities”, and the associated growth of these cities and the transformation of their physical, social and economic environment (Elie’s) Another definition is thus: “An increasing concentration of the population in cities and a transformation of land use to an urban pattern of organization.”
  2. 2. • Urbanization is a global trend, but it is fastest in developing countries which still have a low urban population percentage• It is ongoing: more cities are created and megacities (like Moscow) can grow even bigger
  3. 3. Degrees of urbanizationRural Ex-urban Suburban Urbanurban sprawl:spatial expansion of cities
  4. 4. When and why did humanity start urbanizing? http://en.wikipedia.org/wiki/List_of_cities_by_time_of_continuous _habitation Homo sapiens have existed on earth for about 200,000 years, but cities have existed for less than 10,000 years. A long time ago: ~5000 BC large permanent settlements started appearing around the Mediterranean. Cities needed developed agriculture to produce surplus food outside of cities for them. Maybe because we found cities to be more stable, prosperous and safe (back when cities were better defended against invaders) … in any case the, the main motivations for people to move to urban areas today are economic, and the incentives remain very strong Thus urbanization will continue
  5. 5. Chicago in 1820: population 15
  6. 6. Chicago in 1898: population 1.6 million
  7. 7. Chicago+ in 2012: population 9.5 million
  8. 8. Where are we today? More at: http://www.un.org/esa/population/publications/wup20 07/2007WUP_Highlights_web.pdf
  9. 9. Where are we today?http://esa.un.org/unpd/wup/maps_1_2009.htm
  10. 10. Urbanization and per capita GDP: e.g. China http://www.mckinsey.com/mgi/reports/pdfs/c hina_urban_billion/China_urban_billion_full_r eport.pdf Urban population > 50% ~ 2014 The Economist
  11. 11. So where does this leave us? Urbanization will continue and eventually, at some point, most countries will have urbanization rates > 80% Thus the question is How to Urbanize? And1. preserve the environmental quality in cities2. avoid significant regional and global impacts of urban areas This is where a combination ofpolicy, science, engineering is needed
  12. 12. How does it affect the environment? Changes the surface to solid, impervious material with different thermal properties Changes the topology of the surfaces from low roughness vegetation or porous forests to complex bluff bodies (buildings) Reduces natural water vapor release to the atmosphere (surfaces do not hold water), but Increases the anthropogenic production of heat and water vapor Increases the emissions of air pollutants and greenhouse gases
  13. 13. So is it “bad”?Not necessarily:1. Buildings, with small apartments and shared walls, need less energy to heat and cool than big houses.2. Compact cities reduce commuting and transportation impacts (but create traffic jams that can take back some of these advantages), are more amenable to public transportation solutions (but food and other things might have to be transported from far away) So on average, city residents pollute less and emit less GHG, http://eau.sagepub.com/content/early/2011/01/08/095624781039 2270 http://siteresources.worldbank.org/INTUWM/Resources/GHG_Inde x_Mar_9_2011.pdf
  14. 14. Per capita, city residents emit less GHGs Thanks Liuye 5.5 2005 …except in developing countries where the urban population is much richer than rural populations http://eau.sagepub.com/content/early/2011/01/08/0956247810392270
  15. 15. But it is concentrated Higher density means all of these impacts are concentrated rather than diluted. Urban environmental problems are very local: cities cover ~ 3-4% of the earth’s land surface (http://www.livescience.com/6893-cities-cover-earth- realized.html) Cities can have an impact on regional climate and environment, especially if large or concentrated (10% of coastal areas are urbanized  coastal cities) Cities can have serious impacts on water quality in adjacent water bodies and need very large waste landfills Unlikely to have a major direct impact on global climate! …yet
  16. 16. Environmental Footprint of Cities 1 An environmental footprint, of a product, city, or process, is the equivalent land surface needed to sustainably produce the material, food, and other items needed to make the product, sustain the city’s activity, or perform the process. (Read “Our ecological Footprint: Reducing Human Impact on the Earth” by Wackernagel and Rees) London has an area of 170,000 ha but an environmental footprint of 21,000,000 ha. On average, slum dwellers in New Delhi, India, require only 0.8 hectares of land per capita to maintain their minimal lifestyles, while Americans in Boston or New York need 8.4 hectares of land per capita to support their consumption levels. http://ww2.unhabitat.org/cdrom/wuf/documents/Dialogues/Added%20m aterial%20during%20WUF%20II/Urban%20Sustainability/Presentation%20 by%20Mr.%20Bakary%20Kante.pdf
  17. 17. Environmental Footprint of Cities 2 Another possible use of “environmental footprint of a city” is to indicate the surrounding area where the impacts of the city are directly felt, maybe in terms of air quality, hydrometeorological parameters, or other environmental variables. Areas in red depict the dimensions of the main aerosol mass emanating from Beijing during the opening weekend of the Summer Olympics. Models predict cleaner skies in the starting days of the Games. Image: Greg Carmichael/University of Iowa.
  18. 18. So the question is How to Urbanize more sustainably? Improve the functioning of existing cities Building better future cities But cities are complex and we need to understand individual processes, how they interact, and how they function together in the “urban system”
  19. 19. Large Picture: Urban Systems Modeling Each subprocess is complex Processes Interact & competehttp://www.cdm.com/en-us/Insights/Neysadurai-Centre/Urban-Systems-

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