http://exploredia.com/world-population-2011/

Why should we care about cities?

Throughout human history, most humans have NOT lived in cities.

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/

http://worldkit.org/population/

By 1900, ~14 percent of the global population lived in cities and ~ 15 cities had > 1 million people.

In 1950, 30 percent of the world's population lived in cities and the number of cities with over 1 million

people had grown to 83.

http://worldkit.org/population/

In 2008, for the first time, the world's population was evenly split between urban and rural areas and there were

more than 400 cities with over 1 million people.

53% lived in cities with < 500,000 people

38% lived in cities with > 1 million people.

15% lived in cities > 5 million people

Distribution of the world’s urbanites in 2008

http://www.prb.org/Educators/TeachersGuides/HumanPopulation/Urbanization.aspx

(Grimm et al., 2008)

Today, 74 % of people in industrialized countries live in urban areas and 44

percent 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

Megacities in 2002

There are currently ~ 26 megacities with more than 10 million people!

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http://www.nationsonline.org/oneworld/most_pop_cities_usa.htm

Seattle

3) Chicago metro area 9.4 million

4) Philadelphia metro area 5.8 million

1) NY City metro area 18.7 million

5) Dallas-Fort Worth metro area

5.8 million

2) LA metro area 12.9

million Honolulu

Puerto Rico

Only 8 % of Americans live in cities with populations > 1 million

0 100 10,000 people per sq. mile

http://i.bnet.com/blogs/usa-population-time-2006-joe-lertola-edit.jpg

WHICH ARE THE LARGEST? WHY PUBLISHED POPULATIONS FOR MAJOR WORLD URBAN AREAS VARY SO GREATLY

RL Forstall, RP Greene and JB Pick

Abstract:

Lists of the world’s largest urban areas according to population size are surprisingly inconsistent in standard reference sources. These even disagree about which area is the world’s largest. In this paper we first review the differences found in the population reporting of the twenty largest world urban areas by several unofficial sources and by the United Nations. We then demonstrate that variations in the populations and rankings stem primarily from differences in concepts and definitions, not from bad census counts or lack of basic information about the individual urban areas. http://www.uic.edu/cuppa/cityfutures/papers/webpapers/cityfuturespapers/session3_4/3_4whicharethe.pdf

urban agglomeration = a central city (or cities) surrounded by continuous urban areas

metropolitan area = a large urban nucleus together with adjacent areas with a high degree of economic and social integration

city proper = an incorporated administrative district with specific boundaries beyond which urban development has often overflowed

3 terms used to define urban areas

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More than 95% of the net increase in global population during the 21st century is projected to occur in cities in

developing countries

http://maps.grida.no/go/graphic/urban_population_status_and_trends

Almost 40 percent of city dwellers in developing countries (~ 1 billion people) live in slums

Variation in urban population density

If all the people on planet Earth lived in one city, how large would that city be?

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Urban areas depend on the productive and assimilative capacities of ecosystems well

beyond their formal boundaries, i.e., land tens to hundreds of times larger than the area a

city physically occupies is required to produce the energy, material goods, and nonmaterial

services (including waste absorption) that sustain the city.

(Grimm et al., 2008)

http://www.unep.org/yearbook/2004/010b.htm

Human appropriation of net primary production (NPP), as a per cent of total NPP. The local consumption rate of NPP is compared to the

local production rate of NPP. Highly populated areas (yellow and red) consume up to 300 times their local production.

Source: Imhoff and others 2004

Historians speculate that excessive resource demands (especially by elites) led to

degradation of surrounding landscapes and eventual collapse of many ancient cities.

Tikal

Babylon Angkor

During the 18th and 19th centuries demand by European cities for wood deforested colonial lands and more

recently, demand for beef by Western cities has transformed New World tropical rainforests into pastures.

http://www.nomadicminds.org/blogs/2010/06/

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

Almost 900 of these giant stone sculptures were carved and transported - some weighing over 80 tons

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)

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. .

(Grimm et al., 2008)

Shortages of construction materials such as metals, coal, cement, and timber are likely to constrain China’s

urbanization in the long term, and exert pressure on urban infrastructure development worldwide

For most of the 20th century, most ecologists ignored urban 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 the United States, urban ecology also has begun to change

the discipline of ecology.

(Grimm et al., 2008)

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Residential landscapes are a critical ecological feature of the urban ecosystem 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 Sonoran desert ecosystems have been replaced by an “urban oasis” that includes both lush, watered lawns and carefully-managed desert-like landscapes. CAP’s socio-ecological research has delved into the household decision-making, perceptions, and priorities that result in particular residential landscapes.

~32 million acres of lawn!

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

Some stats to consider

1) The review of Gimme Green at the following link: http://www.gimmegreen.com/media%20articles/Newsleader.htm includes an interesting quote towards the end – “Some documentaries “fall on the preachy side (and) turn people off… Others antagonize and attempt to make people look foolish. That’s not my style at all”. What do you think? Does the film avoid getting 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 the film? 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.

Bring written answers to the following questions to class tomorrow.

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

person's relationship with their lawn and how you think they would respond if they watched the film Gimme Green. If not, describe how you

think one of the specific people interviewed in the film would react to the film.

6) Considering the negative environmental impact of intensively managed lawns, 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.

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 the

metabolism analogy but interest in urban metabolism has led to informative analysis of long-term trends in

the flow of energy, paper, plastics, metals and food stuffs in, out and within cities.

What is urban metabolism?

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The Changing Metabolism of Cities (Kennedy et al., 2007)

Fresh water consumption and waste water production by cities

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.

Low flow-discharge from cities also contribute to pollution downstream in the form of automotive

chemicals, pesticides, pet wastes, persistent organic pollutants...

Stormwater is conveyed separately from sewage in cities with relatively new infrastructure but are mixed in older European and American cities, creating acute pollution

events every time large rainfall events occur.

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1 gallon of gasoline per day

How much gasoline do you consume per day?

Adapted from (Newman and Kenworthy, 1991)

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 energy on 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.

The City Solution Why cities are the best cure for our planet's growing pains

December 2011

Seoul, Korea

Large cities are concentrations of human ingenuity and efficiency and generally require far fewer resources on a per capita basis than

small towns or rural areas.

“Possibly the most exciting book on ecology or environmentalism to be published in several years, David Owen's Green Metropolis: Why Living Smaller, Living Closer, and Driving Less Are the Keys to Sustainability challenges the conventional wisdom of the environmental movement and uses Ney York City (not Portland Oregon or rural Vermont) as a model of true sustainability. Owen's seemingly counter-intuitive argument is supported by the data: New Yorkers have the lowest per capita energy consumption and smallest per capita carbon footprint of anyone in the United States. The key to this isn't that New Yorkers are morally superior or ideologically predisposed to environmentalism, but simply the structure of the city: “Manhattan's density is approximately 67,000 people per square mile, or more than eight hundred times that of the nation as a whole and roughly thirty times that of Los Angeles.”

http://nefac.net/greenmetro

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.

The high cost of suburban living is subsidized by the rest of the population in the form of highway

construction, extension of water and sewer lines, and running electricity to new subdivisions at taxpayer

expense.

If the true cost of sprawl were borne by developers and suburban home-buyers, in the form of increased housing prices, higher property taxes, infrastructure

recovery costs included in utility bills, and tolls placed on highways used primarily by commuters, the

suburbs would look much less attractive.

City Hall, Chicago

Positive human experiences with nonnative, global “homogenizers”, such as pigeons, may be essential for convincing urbanites of the importance of conserving

global biodiversity.

With an ever-increasing fraction of humans living in cities, encounters with urban nature have supplanted experiences

with natural biodiversity for many people.

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 on around 4 percent of the arable land, leaving

more space for nature.