urbanization in the 21 century: challenges and...
TRANSCRIPT
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