Urbanization in the 21st century: Challenges and opportunities for

environmental sustainability

Peter J. Marcotullio and Karen C. Seto

(Source: UN DESA 2012)

Global trends in urban population

Global trends in urban land use

• Current global urban built up area includes 73 million hectares.

• Urban expansion to 2030 may include an additional 153 million hectares (Seto et al. 2011).

This translates to adding to an an area slightly larger

than the size of Texas, areas the size of another Texas, California, Montana and Massachusetts

Challenges and opportunities with global urbanization for environmental sustainability

• Challenges

– Direct impact on environment • Habitat loss and fragmentation, agricultural land loss,

altered biogeochemical cycles and hydrology from the creation of urban infrastructure

• Consumption of wood, cement, iron, steel, etc., for the building of cities

– Provisioning deficient and up-grading

– Indirect impact related to increased consumption, wastes and emissions from wealthy urban residents

Global Urban Extent 2030

(Seto et al. 2012. PNAS)

Average (MgC/ha) and total C (PgC) loss by region within pantropics

Total C loss across pantropics: 1.38 PgC ≡ 0.05 PgC yr−1

∼5% of emissions from tropical deforestation (Seto et al 2012 PNAS )

Energy consumption with urbanization

Source: Jiang and Lin, 2012 Energy Policy 49(10)

Source: Shen et al 2005 Cities 22(4)

Urbanization and direct materials consumption

+25% +28% +41 +345% +63% +420% +29% +242%

Source: Shen et al 2005 Cities 22(4)

Urbanization and direct materials consumption

Informal residential development can be seen expanding into agricultural lands on the fringe of Cairo, Egypt between 2002 (left) and 2010 (right). (Slide by S. Angel)

Challenges of urbanization: Providing infrastructure in the developing world

Source: WHO / UNICEF 2012

Challenges of urbanization: Providing infrastructure in the developing world

More people have a mobile than a toilet

Source: WHO / UNICEF 2012

Challenges of urbanization: Providing infrastructure in the developing world

More people have a mobile than a toilet

Challenges of urbanization: Aging infrastructure in the developed world

Challenges and opportunities with global urbanization for environmental sustainability

• Opportunities of urbanization

– Agglomeration economies in production and consumption

– Low carbon transportation and energy consumption

– Scaling benefits of increasing urban populations

Quigley 1998 Journal of Economic Perspectives 12(2)

Urbanization also bring opportunities: economic productivity

Source: Ciccone and Hall 1996 American Economic Review 86(1)

Urbanization also bring opportunities: economic productivity

Labor productivity increases by ~ 6 percent with a doubling of employment density.

Glaeser et al 2001 Journal of Economic Geography 1(1)

Urbanization also bring opportunities: consumer cities

Glaeser et al 2001 Journal of Economic Geography 1(1)

Urbanization also bring opportunities: consumer cities

Source: Carlino et al 2007 Journal of Urban Economics 61(3)

Urbanization also bring opportunities: innovations

Inventions/person increase by ~20 percent with a doubling of density

http://www.grida.no/

Urbanization also bring opportunities: Less transportation carbon emissions

• The literature suggests that doubling residential density might lower household VMT by about 5 to 12 percent, and perhaps by as much as 25 percent, if coupled with higher employment concentrations, significant public transit improvements, mixed uses, and other supportive demand management measures.

• Scenarios developed by the committee suggest that significant increases in more compact, mixed-use development will result in modest short-term reductions in energy consumption and CO2

emissions, but these reductions will grow over time.

Urbanization also bring opportunities: Less transportation carbon emissions

In the USA, at the observed average cost of $231 million and $53 million per mile, the average heavy-rail and light-rail systems in cities need around 45 and 30 people per gross acre around stations to achieve a high cost-effectiveness rating (Cervero and Guerra 2011).

Both light and heavy rail require population densities around stations to be cost effective.

Urbanization also bring opportunities: Thresholds for low-carbon transportation

Urbanization also bring opportunities: Thresholds for low-carbon transportation

“Heat maps” combine the following variables: Population density Employment density Proximity to Universities Available bicycle infrastructure Proximity to tourist locations Available transit Topography

Bike Sharing in the United States: State of the Practice and Guide to Implementation 17

3.1 SELECTING A SERVICE AREA

Higher use bike share stations tend to be located

in higher density areas (i.e. those areas with higher

population and job rates, and with higher levels of

commercial activity), and with high levels of pedestrian

activity. Topography is also an important consideration

related to service area siting. Implementation of a system

may be more complicated in jurisdictions with steep (or

even rolling) terrain.33 Jurisdictions with steep slopes

may want to consider, to the degree that this is possible,

initial implementation in parts of the community that

are relatively at. Finally, the size of the service area will

be dependent on the size of the jurisdiction. Existing

bike share programs in the U.S. that were part of this

analysis include a service area coverage of 1.5 square

miles (Spartanburg, SC) to 36 square miles (Washington

DC area).34

Many bike share programs have developed “heat maps”

that help to de ne the initial service areas for the system.

e following are typical factors in the development of

these maps:

Population Density: Higher population densities

tend to support higher bike share demand by

providing a pool of regular users. Higher population

densities tend to correlate with reduced rates of auto

ownership as well.35

Employment Density: Higher employment density

yields greater access to potential bike share users.

Employment density and location can also help

determine how the pattern of morning commute

may a ect the distribution of bike share rides

throughout the service area.

Proximity to Colleges and Universities: Student

populations can be a likely market for bike

sharing programs because of their lower rates of

automobile ownership. Universities located in

urban settings tend to be surrounded by mixed-

use development which further supports bike

share usage.36

Retail/Commercial Activity Density: Commercial

activity is usually included in the analysis because of

its function as a trip attractor and its potential to have

an e ect on ridership and distribution of bicycles.

Available bicycle infrastructure: Bicycle lanes,

bike boulevards, cycle tracks and shared use paths

provide supporting infrastructure for bike share

users and should be included in the analysis.37

Proximity to tourist attractions and recreation

areas: Bike share rides generated by tourists have

the potential of becoming a considerable source

of revenue for a bike share system.38 Some tourist

areas are congested, putting pressures on existing

transportation infrastructure. A bike share program

increases mode share choices and providing quicker

access to recreational areas.

Available Transit: In large cities, bike sharing

programs are o en organized to provide better

service for the rst and/or last mile of a trip taken

on public transit. e goal is to create a connected

transportation experience with less time used for

transfers and access to and from the transit service.

Topography: Steep inclines can be a deterrent to

bicycling. Slopes at a grade of 4% or higher are

considered a major barrier for bicyclists.39 Existing

systems reported lower usage to stations that are

located in higher elevations within the system,

which creates challenges for redistribution.40

In most instances, a phased approach to implementation

may be the best way to ensure jurisdiction-wide access

and buy-in necessary to get the program launched.

Figure 15: Heat map analysis (City of Pittsburgh)

Source: Feasibilit y Study for a potential bike share program in the city of Pittsburgh

Source: US DOT, 2012

Urbanization also bring opportunities: Thresholds for low-carbon transportation

Citi Bike hit 100,000 customer mark in just 10 days after initiation of the program. During this period, these riders traveled more than 270,000 miles — greater than the distance to the moon. Source: Daily News, 2013

Source: Norman et al 2006 Journal of Urban Planning and Development 132(1)

More compact urbanization brings lower energy consumption and emissions

Life cycle assessment of 2 neighborhoods in Toronto

GHG emissions

(tons CO2-eq./capita)

Africa 2.1 Urban 1.5-2.1

Non-urban 2.1-2.3 Asia 3.8

Urban 3.3-4.2 Non-urban 3.6-4.1

Latin America 5.0 Urban 2.4-2.8

Non-urban 7.3-7.8 Europe 11.4

Urban 8.7-10.7 Non-urban 12.4-15.3

North America 23.8 Urban 15.9-23.5

Non-urban 24.5-45.7 Oceania 20.6

Urban 11.6-19.2 Non-urban 22.2-31.0

World 5.7 Urban 5.2-6.9

Non-urban 4.9-6.1 Developing 3.43

Urban 2.6-3.3 Non-urban 3.5-3.9

Developed 15.0 Urban 10.9-14.5

Non-urban 16.0-22.8

Source: Marcotullio et al Climatic Change (under review)

Urbanization also bring opportunities: Lower emissions…in highly urbanized systems

Source: Bettencourt, L., et al., 2007 PNAS 104(17)

These results indicate that scaling is indeed a pervasive property of urban organization.

Increasing urban population can bring opportunities: Scaling functions

82% increase

35% decrease

(Guneralp and Seto. 2012. Applied Geography)

Caveat: Efficiency gains can be overshadowed by the scale of urban expansion

More space to cool

(Guneralp and Seto. 2012. Applied Geography)

Caveat: Efficiency gains can be overshadowed by the scale of urban expansion

(Guneralp and Seto. 2012. Applied Geography)

Caveat: Efficiency gains can be overshadowed by the scale of urban expansion

(Guneralp and Seto. 2012. Applied Geography)

Caveat: Efficiency gains can be overshadowed by the scale of urban expansion

A 25% decrease in energy required per tonne of concrete in China.

A 300% increase in annual CO2 emissions due to concrete used in building construction.

(Seto et al. 2012. PNAS)

Future urbanization provides opportunities for building better cities

65% of the urban land cover on the planet in 2030 have yet to be built