Urban ecology

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This is a slightly updated set of Urban Ecology slides that I am sharing with my Soil and Water Conservation class

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Urban ecology

  1. 1. Why should we care about cities? http://exploredia.com/world-population-2011/
  2. 2. Throughout human history, most humans have NOT lived in cities.
  3. 3. In 1800, only 3 percent of the global population lived in cities and only 1 city had more than 1 million people. http://worldkit.org/population/
  4. 4. By 1900, ~14 percent of the global population lived in cities and ~ 15 cities had > 1 million people. http://worldkit.org/population/
  5. 5. In 1950, 30 percent of the worlds population lived in cities and the number of cities with over 1 million people had grown to 83. http://worldkit.org/population/
  6. 6. In 2008, for the first time, the worlds population wasevenly split between urban and rural areas and there were more than 400 cities with over 1 million people.
  7. 7. Distribution of the world’s urbanites in 2008 53% lived in cities with < 500,000 people 38% lived in cities with > 1 million people. 15% lived in cities > 5 million peoplehttp://www.prb.org/Educators/TeachersGuides/HumanPopulation/Urbanization.aspx
  8. 8. (Grimm et al., 2008)
  9. 9. Today, 74 % of people in industrialized countries live in urban areas and 44percent of people in developing countries live in urban areas.It is expected that world population will be 70 percent urban by 2050. http://www.prb.org/Educators/TeachersGuides/HumanPopulation/Urbanization.aspx
  10. 10. Megacities in 2002
  11. 11. There are currently ~ 26 megacities with more than 10 million people!
  12. 12. http://en.wikipedia.org/wiki/Megacity
  13. 13. http://www.nationsonline.org/oneworld/most_pop_cities_usa.htm
  14. 14. 1) NY City 3) Chicago metro area metro area 9.4 million 18.7 million Seattle 4) Philadelphia metro area 5.8 million2) LA metro Puerto area 12.9 Rico million Honolulu 5) Dallas-Fort Worth metro area 5.8 million Only 8 % of Americans live in 0 100 10,000 people per sq. mile cities with populations > 1 million http://i.bnet.com/blogs/usa-population-time-2006-joe-lertola-edit.jpg
  15. 15. WHICH ARE THE LARGEST? WHY PUBLISHED POPULATIONS FOR MAJOR WORLD URBAN AREAS VARY SO GREATLY RL Forstall, RP Greene and JB PickAbstract:Lists of the world’s largest urban areas according topopulation size are surprisingly inconsistent in standardreference sources. These even disagree about which area isthe world’s largest. In this paper we first review thedifferences found in the population reporting of the twentylargest world urban areas by several unofficial sources and bythe United Nations. We then demonstrate that variations inthe populations and rankings stem primarily from differencesin concepts and definitions, not from bad census counts orlack of basic information about the individual urban areas.http://www.uic.edu/cuppa/cityfutures/papers/webpapers/cityfuturespapers/session3_4/3_4whicharethe.pdf
  16. 16. 3 terms used to define urban areascity proper = an incorporated administrative districtwith specific boundaries beyond which urbandevelopment has often overflowedurban agglomeration = a central city (or cities) surrounded by continuous urban areasmetropolitan area = a large urban nucleustogether with adjacent areas with a high degree ofeconomic and social integration
  17. 17. http://www.uic.edu/cuppa/cityfutures/papers/webpapers/cityfuturespapers/session3_4/3_4whicharethe.pdf
  18. 18. More than 95% of the net increase in global populationduring the 21st century is projected to occur in cities in developing countries http://maps.grida.no/go/graphic/urban_population_status_and_trends
  19. 19. Almost 40 percent of city dwellers in developing countries (~ 1 billion people) live in slums
  20. 20. Variation in urban population density
  21. 21. If all the people on planet Earth lived in one city,http://marcgawley.com/ how large would that city be?
  22. 22. Urban areas depend on the productive and assimilative capacities of ecosystems wellbeyond their formal boundaries, i.e., land tens to hundreds of times larger than the area acity physically occupies is required to produce the energy, material goods, and nonmaterial services (including waste absorption) that sustain the city. (Grimm et al., 2008)
  23. 23. Human appropriation of net primary production (NPP), as a per cent of total NPP. The local consumption rate of NPP is compared to thelocal production rate of NPP. Highly populated areas (yellow and red) consume up to 300 times their local production. Source: Imhoff and others 2004 http://www.unep.org/yearbook/2004/010b.htm
  24. 24. Historians speculate that excessive resource demands (especially by elites) led to degradation of surrounding landscapes and eventual collapse of many ancient cities.Angkor Babylon Tikal
  25. 25. During the 18th and 19th centuries demand by European cities for wood deforested colonial lands and more recently, demand for beef by Western cities hastransformed New World tropical rainforests into pastures.
  26. 26. Almost 900 of these giant stone sculptures were carved and transported - some weighing over 80 tons Pollen analysis has now established that Easter Island was almost totally forested until 1200 CE. The tree pollen disappeared from the record by 1650, and the statues stopped being made around that time http://www.nomadicminds.org/blogs/2010/06 /
  27. 27. The unprecedented rates of urban population growth over the past century have occurred on <3% of the global terrestrial surface, yet the impact has been global, with 78% of carbon emissions, 60% of residential water use, and 76% of wood used for industrial purposes attributed to cities. Land use change directly associated with building cities as well as supporting the demands of urban populations drives many other types of environmental change. (Grimm et al., 2008)
  28. 28. In China alone, 300 million rural people are likely move to cities in the next few decades transforming their home landscapes and driving onward unprecedented rates of urban construction. . Shortages of construction materials such as metals, coal, cement, and timber are likely to constrain China’surbanization in the long term, and exert pressure on urban infrastructure development worldwide (Grimm et al., 2008)
  29. 29. For most of the 20th century, most ecologists ignoredurban areas with the result that ecological knowledge contributed little to solving urban environmental problems.Recently, however, ecologists have begun collaborating with other scientists, planners, and engineers to understand and even redesign urban ecosystems. With the advent 10 years ago of National Science Foundation–funded urban research programs in theUnited States, urban ecology also has begun to change the discipline of ecology. (Grimm et al., 2008)
  30. 30. http://caplter.asu.edu/
  31. 31. Residential landscapes are a critical ecological feature of the urbanecosystem because they are widespread and are made up of highly-designed and managed combinations of plants (e.g. landscaping)and animals (e.g. pets). As Phoenix has urbanized, native Sonorandesert ecosystems have been replaced by an “urban oasis” thatincludes both lush, watered lawns and carefully-managed desert-likelandscapes. CAP’s socio-ecological research has delved into thehousehold decision-making, perceptions, and priorities that result inparticular residential landscapes.
  32. 32. ~32 million acres of lawn!
  33. 33. Some stats to consider Residential lawns occupy ~ 20 million acres in the US. US lawn care industry annual revenue exceeds $40 billion. > $ 5 billion is spent on fertilizer for U.S. lawns.A typical power lawnmower pollutes as much in one hour as driving an automobile for 20 miles. 60 to 70 thousand severe accidents, some fatal, result from lawnmower use, as well as significant damage to human hearing. ~ 70 million pounds of pesticides are used each year on lawns
  34. 34. Bring written answers to the following questions to class tomorrow.1) The review of Gimme Green at the following link:http://www.gimmegreen.com/media%20articles/Newsleader.htmincludes an interesting quote towards the end – “Some documentaries “fall on thepreachy side (and) turn people off… Others antagonize and attempt to make peoplelook foolish. That’s not my style at all”. What do you think? Does the film avoidgetting preachy? Does the film avoid antagonizing/making people look foolish?2) Overall, do you think this review does a good job of capturing the essence of thefilm? Discuss your answer.3) Spend a little time looking at the Gimme Green website http://www.gimmegreen.com/Describe a few interesting things you learned specifically from the website.
  35. 35. 4) Did you think the film was humorous? If so, comment on some of the more humorous moments in the film.5) Do you know anyone who is obsessed with their lawn or at least is very committed to maintaining a nice looking lawn? If so, briefly discuss this persons relationship with their lawn and how you think they would respond if they watched the film Gimme Green. If not, describe how youthink one of the specific people interviewed in the film would react to the film.6) Considering the negative environmental impact of intensively managedlawns, do you think there should be public policies to discourage lawns or encourage alternatives to lawns? 7) Has your perspective on lawns changed at all as a result of watching the film? Explain.
  36. 36. What is urban metabolism?A key concept within the discipline of urban ecology is urban metabolism which compares the flows of energy and materials in and out of cities and the transformation and accumulation of energy and materials within cities to biological metabolism. Some scientists debate the appropriateness of themetabolism analogy but interest in urban metabolismhas led to informative analysis of long-term trends in the flow of energy, paper, plastics, metals and food stuffs in, out and within cities.
  37. 37. Fresh water consumption Fresh water consumption and waste water production by cities waste water production 150 (gal/day/person) 75 The Changing Metabolism of Cities (Kennedy et al., 2007)
  38. 38. Throughout history, cities have sprung up along rivers, because of the available water. Within cities, water is intricately linked to not only domestic use but also industrial processes,transportation, sanitation, and natural disasters (floods, hurricanes, and tsunamis). Thus, humans have modified hydrosystems to meet a large array of often conflicting goals. Designed or altered streams, rivers, flood channels, canals and other hydrosystems serving urban areas neither replicate the aquatic ecosystems they replace nor preserve the ecosystem services lost.
  39. 39. Stormwater is conveyed separately from sewage in citieswith relatively new infrastructure but are mixed in older European and American cities, creating acute pollution events every time large rainfall events occur. Low flow-discharge from cities also contribute to pollution downstream in the form of automotive chemicals, pesticides, pet wastes, persistent organic pollutants...
  40. 40. How much gasoline do you consume per day?(Gigajoules/year/person) 1 gallon of gasoline per day Adapted from (Newman and Kenworthy, 1991)
  41. 41. Many factors influence the metabolism of cities Sprawled, low-density cities have higher per capita transportation energy requirements than compact cities.Cities with interior continental climates expend more energyon winter heating and summer cooling than those with more temperate climates. Application of technology, appropriate use of vegetation and the costs of energy influence energy consumption. Public policies (e.g., building codes and recycling programs) and social attitudes impact material and energy flows.Lastly, the age of a city, its overall infrastructure, and its stage of industrial development impact its urban metabolism.
  42. 42. The City Solution Why cities are the best cure for our planets growing painsDecember 2011 Seoul, Korea
  43. 43. Large cities are concentrations of humaningenuity and efficiency and generally requirefar fewer resources on a per capita basis than small towns or rural areas.
  44. 44. “Possibly the most exciting book on ecology or environmentalismto be published in several years, David Owens Green Metropolis:Why Living Smaller, Living Closer, and Driving Less Are the Keys toSustainability challenges the conventional wisdom of theenvironmental movement and uses Ney York City (not PortlandOregon or rural Vermont) as a model of true sustainability.Owens seemingly counter-intuitive argument is supported by thedata: New Yorkers have the lowest per capita energy consumptionand smallest per capita carbon footprint of anyone in the UnitedStates. The key to this isnt that New Yorkers are morally superioror ideologically predisposed to environmentalism, but simply thestructure of the city: “Manhattans density is approximately67,000 people per square mile, or more than eight hundred timesthat of the nation as a whole and roughly thirty times that of LosAngeles.” http://nefac.net/greenmetro
  45. 45. City dwellers tread more lightly in many ways, David Owen explains in Green Metropolis. Their roads, sewers, and power lines are shorter and so use fewer resources. Their apartments take less energy to heat, cool, and light than do houses. Most important, people in dense cities drive less.Their destinations are close enough to walk to, and enough people are going to the same places to make public transit practical. In cities like New York, per capita energy use and carbon emissions are much lower than the national average.
  46. 46. The high cost of suburban living is subsidized by the rest of the population in the form of highwayconstruction, extension of water and sewer lines, and running electricity to new subdivisions at taxpayer expense. If the true cost of sprawl were borne by developersand suburban home-buyers, in the form of increased housing prices, higher property taxes, infrastructurerecovery costs included in utility bills, and tolls placed on highways used primarily by commuters, the suburbs would look much less attractive.
  47. 47. City Hall, Chicago
  48. 48. With an ever-increasing fraction of humans living in cities,encounters with urban nature have supplanted experiences with natural biodiversity for many people. Positive human experiences with nonnative, global “homogenizers”, such as pigeons, may be essential for convincing urbanites of the importance of conserving global biodiversity.
  49. 49. If what you value most is nature, cities look like concentrated piles of damage—until you consider the alternative, which is spreading the damage. Cities allow half of humanity to live onaround 4 percent of the arable land, leaving more space for nature.
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