The Factors of Urban Morphology in Greenhouse Gas Emissions: A Research
Overview
Michael Mehaffy1, Stuart Cowan2, Diana Urge-Vorsatz3
Important note: The following is an interim draft for discussion at the IARU Scientific
Congress, Copenhagen, 10-12 March 2009. Not for circulation.
Introduction
While there is a mature body of research on the greenhouse gas contributions of
individual energy-using devices such as buildings and automobiles, there is a much less
complete picture of the larger systems in which they operate, particularly urban systems.
Yet there is evidence that these systemic effects could potentially determine urban energy
use to an even greater degree than the efficiencies of individual devices or components
such as buildings and vehicles. This finding is therefore likely to have profound
implications in guiding us to effective strategies for the reduction of energy use and the
mitigation of greenhouse gas emissions per capita.
However, quantifying these systemic impacts, and our potential leverage over them, is
significantly more challenging than the quantification of device/building energy use. This
is the result of the many factors that interact in exceedingly complex ways. There is a
lack of data on systemic indicators that are more difficult to measure or quantify, such as
the cause of different trips people make (whether they are induced or mitigated by urban
infrastructure), and energy flux effects as a result of urban density. Other factors include
our poor understanding of qualitative factors, reasons for the choices made about housing
and mobility, and people’s expectations towards comfort and mobility. Furthermore, we
cannot yet fully quantify the impact of trade-offs such as living in a new, very energyefficient, but suburban building versus staying in older, less efficient more central urban
housing that is associated with much lower transport needs. Such choices and factors
determine fundamentally what urban design patterns serve best people’s comfort
requirements, and how these could be optimized from a GHG emission perspective at the
systemic level. At this point, we do not even have a comprehensive model that fully
accounts for the key drivers of urban systemic energy use and their interactions, or a
taxonomy of main determinants of urban energy use – as opposed to the much more
clearly understood technological efficiencies of energy-using devices.
The challenge is further complicated by the fact that urban energy use cuts across sectors
and disciplines. The most typical organization of analysis of global and national energy
systems is by economic sectors, i.e. dividing energy use into industrial, transport, service,
and residential sectors – or similar categories with higher or lower resolution. This is a
convenient frame for analysis since economic data are collected and reported in such
categories, facilitating in-depth and comparable assessment across nations. This logic of
1
Council for European Urbanism, Sustasis Foundation
Autopoiesis LLC, Sustasis Foundation
3
Central European University, IPCC
2
organizing analysis and information is, for instance, used in the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change (IPCC, 2007).
However, a few key energy-using systems represent more important energy-using units
than the boundaries determined by these economic sectors. An example that parallels
that of urban systems is that of food systems. Energy needed for providing food for
people is divided between agricultural energy use, food industry energy use, transport
energy use, food retail energy use, and finally home energy used for cooking and
refrigeration. Individual energy values represent a small share in their respective sectors,
and thus food-related energy rarely leads energy policy agendas. However, if these are
totaled, the combined operations to satisfy the nutritional needs of the population can
amount to a very significant share of total energy consumption. Since there are many
trade-offs between the agricultural energy use, transport use and cooking energy use4 for
optimal policy design, food systems must be considered as a complete system rather than
in the narrow analysis of food transporting vehicles and cooking device efficiency.
Urban energy systems are similar. While policies have effectively reduced energy
consumption of individual buildings and automobiles, they have not necessarily
minimized overall energy use, and in some cases may have even increased it. For
example, there are notable cases of “green buildings” in more remote locations that
require significantly higher transport energy for their users, and may therefore reduce any
gains in energy efficiency, or even result in increased net energy. A US case study by
Environmental Building News (2007) is instructive: it examined the world’s first LEEDTM
Platinum building, the Chesapeake Bay Foundation’s Philip Merrill Environmental
Center, which replaced an urban location with a suburban one. The study concluded that
despite the greater efficiency of the building itself, “the additional energy use from more
employees driving to work may well exceed the energy savings realized by the green
building.” Indeed, the study cites research indicating that for an average US office
building, the energy associated with transportation to and from the building may be as
much as 30% more than the energy use of the building itself – and an even higher
percentage for energy-efficient buildings. (Cited in Environmental Building News, 2007)
This is only one egregious example of how research is beginning to establish a clearer
understanding of the important ways that the dynamics of urban systems affect
greenhouse gas emissions. Indeed, as this paper will summarize, the research indicates
dramatic potential reductions in energy use and emissions in relation to urban
morphology and infrastructure.
The Energy Efficiency of Settlements
4
One example is the shipping of strawberries to Sweden from southern Europe, in comparison to producing
them locally in an energy-intensive greenhouse. The variables and the way they interact are complex: the
energy of heating versus the energy of transport; the impact of local organic agricultural techniques versus
remote industrial scale techniques, which can nonetheless be more efficient; the promotion of increased
consumption of out-of-season foods; and so on.
We may begin with the recognition that cities, and other settlement types, can be treated
as energy-using systems in their own right, with their own varying levels of efficiency.
Clearly they are not mere aggregations of disconnected consumers of energy. Rather, we
are well aware that the distribution of users affects energy consumption required for
transportation, transmission efficiency, and perhaps other related factors. Moreover, we
know that the urban form can produce or mitigate heat island effects, affecting cooling
demands, and can correlate with more or less efficient building morphologies. More
difficult to assess, the form can affect the behavior and consumption patterns of
individual energy users, as they make decisions about a range of possible activities that
affect energy consumption and emissions.
The evidence indicates that that these factors, and possibly others, create major variations
in energy use per person, and major emissions and other contributions to climate change.
The variation is not marginal, but, taken as whole, a significant percentage of all energy
use: the evidence herein will suggest that it is perhaps on the magnitude of one-third of
all energy use. Clearly, then, this is an important area of research and policy, and one
that demands further development.
We will review herein some of the key research to date, and note the additional research
that is needed. We will then proceed to the policy tools that can affect these variables,
and the further work needed in that area as well – we believe, as a matter of great
urgency.
Following are the individual urban factors that we can associate with lower energy use
and emissions.
Density. This metric includes residential density (usually measured in persons per
hectare, or sometimes households per hectare), and the density of other uses such as
office. It can also be measured as a ratio of the area of building floors to land area – or
“Floor Area Ratio”. Most studies look only at residential density, and then assume a mix
of uses including residential, commercial and office.
The associations between density and energy use are striking. Studies consistently show
that a doubling of density is associated with a reduction in energy use per capita of 30%
or more (Holtzclaw et al.,2002).
One of the strongest reductions is in
transportation energy, which is particularly
significant in areas that have higher personal
automobile use. A classic study in the field
(Kenworthy and Laube, 1999) demonstrated
that transportation fuel consumption per
capita declines by one-half to two-thirds as
urban densities rise from four to twelve
persons per acre (1.6 to 4.8 persons per
hectare).
It is clear that much of this effect comes from the
reduction in required driving that is associated with
density. Studies show a remarkable consistent
association between density and vehicle miles or
kilometers traveled per household. In US research
(Holtzclaw, 2001) the reduction is from about 15,000
miles per year (9,000 kilometres) at a residential
density of 12 units to the acre (5 to the hectare) down
to about 5,000 miles per year (3,000 kilometres) at 75
units to the acre (30 to the hectare).
Global examples are equally striking. The lowerdensity cities of the US (typically 10 persons to the
hectare or less) use about five times more energy in
motor spirit than the cities of Europe, which are in
turn about five times more dense on average. This relationship holds even when
adjustments are made for economic factors. (Kenworthy and Laube, 1999.)
Hidden Energy of Auto Use
2%
1%
Direct Tailpipe
Emissions
3%
Fuel Production
10%
Vehicle Manufacturing
17%
HFC Leakage
67%
Maintenance
Road Network
But it is also clear that the direct
emissions from automobile tailpipes are
only the beginning of the story. For
example, Canadian research shows that
fuel production, vehicle manufacturing,
vehicle maintenance, road construction
and maintenance, and leakage of
refrigerants, account for fully half again
the emissions of tailpipes. (Summarised
in Hydro-Québec, 2005.)
As noted above, often the energy savings from density meet or exceed the savings from
energy-efficient building systems. For example, a compilation study by Holtzclaw et al.
reported by New Urban News (2005)
showed that the savings from an
increase in residential density from
2.5 units per acre (1 per hectare) to
12 units per acre (4 units per hectare)
exceeded the savings from the
maximum rating of the US “Energy
Star” certified heating and domestic
appliances. Increasing density
further to 100 units per acre (40 per
hectare) doubled the energy savings
per household.
We can observe the same dramatic variation
in urban energy use associated closely with
density, even within a single metropolitan
area. This helps us to exclude such factors
as climate variations, cultural differences,
and other regional variations. A particularly
striking example is from a study by the Bay
Area Metropolitan Transportation
Commission in the San Francisco Bay area
of the US. It shows a dramatic tripling of
energy use and CO2 emissions from
transport, moving from the high-density
neighborhoods of San Francisco, out to the
sprawling subdivisions of the suburban
edge. (Bay Area Metropolitan
Transportation Commission, 2007.)
The specific metric is CO2 emissions from
transportation per household, but we can see
a similar reduction in energy in other areas
(as we will discuss in more detail below).
In this case we know a great deal about the factors that vary in the urban structure at the
two extremes. We know that in the suburban edges, residents are required to drive long
distances to work and to daily needs, and that they live more often in single-family
detached dwellings on fragmented street networks. We know that in the high-density
areas, residents can often walk or take transit to destinations that are, on average, much
closer to one another, in a highly integrated street network. We also know that
socioeconomic factors do not explain the disparity – the San Francisco area is hardly
impoverished - nor does climate, regional culture or other factors, as the two locales are
less than 40 miles apart.
Sprawling, fragmented urban patterns in Milpitas, CA., versus compact, walkable urbanism in San Francisco.
Intriguingly, this pattern of greater efficiency is not confined only to transport. Evidence
that we will discuss below shows us that home energy consumption, embodied energy in
construction and maintenance, and other more indirect sources of consumption also vary
greatly as a result of urban form. And while density is closely associated with these other
sources, each of them plays its own distinctive role.
Thus we may think of density as closely associated with, but not synonymous with, a
number of other characteristics of urban structure. It is important to analyse these factors
in their own right, and the aggregate and systemic contributions they make. We may list
them as follows:
Transportation Efficiency. This includes all the factors that promote lower-energy use
in urban transportation. They include:
o Proximity of daily needs and activities. A good mix and distribution of
workplaces, retail, offices and other daily destinations results in
significantly shorter trips per day on average. . (Kenworthy and Laube,
1999.)
o Availability of effective, safe and convenient public transport. An
average single-occupancy passenger sedan consumes 4,200 kilojoules per
passenger-kilometer, while a 40% occupied subway consumes 280
kilojoules per passenger-kilometer (just 6.7%). A 50% occupied diesel
bus consumes 800 kilojoules per passenger-kilometre. (Energy
Information Administration, 2005)
o Walkability. Walking is a very low-energy form of transportation - even
when taking into account the food required to fuel it. Assuming the fuel is
cereal, walking consumes approx. 150 kilojoules per passenger-kilometer
(Summarised in Hydro-Québec, 2005.) Walking trips fueled by a partial
meat diet can be somewhat higher. Moreover, the beginning or end
segment of a public transport trip is almost always a walking segment.
Therefore a neighbourhood that obstructs walkability (through lack of
sidewalks, dangerous streets and so on) is likely to obstruct transit use as
well.
o Bikability. Biking is also a low-energy form of transport, just 60
kilojoules per passenger-kilometre when fueled by cereals. (Various,
summarised in Hydro-Québec, 2005.)
o Urban network. An integrated rather than fragmented urban network
results in shorter trips on average, and proportionately lower energy use
per trip. It also promotes walking, as average walking trips are also
shorter. [Pushkar et al., 2000, Dill, 2004.]
Infrastructure efficiency. It is intuitively obvious, and confirmed by research, that
higher density reduces the allocation of required infrastructure per person.
o Infrastructure construction and maintenance. A one-block street
segment that embodies a typical 100 million BTUs will be allocated across
8 households at 12 million BTUs per household. But the same street
segment serving 20 households will be allocated at only 5 million BTUs
per household. (Cited in Allen et al., 2004.)
o Operating energy. This includes lighting, pumping, signals, irrigation,
and other urban infrastructure energy systems. Higher density
neighbourhoods require proportionately less operating energy per capita.
(Summarised in Hydro-Québec, 2005.)
o Transmission efficiency and loss. Losses from transmission can be as
high as 7% or more, and there is a clear association with urban form.
Higher density means shorter distances and more efficient distribution.
(Dong, 2006)
o Cogeneration and district energy opportunities. These can be much more
efficient than individual building systems – over 25% more efficient.
They can also reduce transmission losses. (Cited in Allen et al., 2004.)
Energy demands from externalities. So-called “externalities” are factors that are not
usually accounted for in normal economic transactions, but that are showing increasing
signs of profound long-term economic consequence. We are beginning to see clearly tat
the same is true for energy use and carbon emissions.
o Loss of ecosystem services. A low-density urban form consumes more
land and destroys areas that may be contributing valuable “ecosystem
services”, such as water filtration, aquifer recharge and more. The loss of
these services translates into yet more energy demand for pumping, water
purification and the like. [Knapp G., et al., 2005]
o Loss of agricultural lands. Nearby agriculture reduces food miles,
increases nutritional value, generally lowers cost, and generally lowers
energy use per calorie. More distant agriculture relies upon increasingly
greater shipping and energy. [Knapp G. et al., 2005.]
o Heat island/albedo/vegetative cover per person. It is sometimes
mistakenly assumed that low-density residential form reduces heat island
effects. But when examined on a per-capita basis, the reverse is often the
case – particularly for auto-dominated development patterns. The result is
an increased demand on cooling equipment in warm areas and seasons. In
addition, low albedo in pavement and roofing increases planetary
warming, and loss of vegetative cover reduces CO2 absorption – both of
which aggravate warming effects over time, and increase cooling demands
yet further. (Akbari, 2008.)
Associations between urban morphology and building morphology. Higher-density
urban areas by their nature include more multi-family and attached dwellings. Thee have
a number of energy efficiency advantages.
o Urban building type, exposure and orientation. According to U.S. DOE
data, space-heating requirements can be as much as 20 percent less on a
square foot basis for dwellings in multi-unit buildings compared to
detached structures. In addition, building orientation as it is shaped by
urban structure can strongly affect passive solar characteristics, including
excessive solar gain and loss of heat. (Cited in Allen et al., 2004.)
o Prevailing size, and economic factors in same. Residential units in
higher-density areas are typically smaller on average, in large part because
of the higher prices commanded by greater proximity. The increased cost
of homes also may cause a shift away from other forms of consumer
spending, toward home care and improvement. (Cited in Allen et al.,
2004.)
o Embodied energy in building materials. According to University of North
Carolina research, attached dwellings have an average of 750,000 Btu per
sq.ft. of embodied energy in their construction materials versus 790,000
Btu for detached dwellings – a reduction of 5%. (Cited in Allen et al.,
2004.)
Other indirect factors. There are other topics that are more difficult to ascertain, but that
seem equally critical in the final determination of whether people will locate in more
compact, low-energy areas, and adopt lower-energy lifestyles.
o Cognitive and behavioral factors. What factors will induce buyers to live
in higher-density, lower-energy and lower-emissions neighbourhoods?
What character of neighborhoods, of architecture? What will promote
lower-energy habits and choices? Much more research is needed in this
important subject, but we know that the success of these neighbourhoods
in attracting and retaining residents over time depends on attractive
architecture, durable high-quality construction, and access to parks and
natural areas (Holtzclaw, 2001).
o Induced demand. This is a well-known perverse effect of efficiency. As
systems become more efficient, they also tend to become less expensive.
The result is that people may be more likely to use them more, partially or
wholly erasing the gains from efficiency (Allen, 2001; Johnston, 2006;
McNally et al., 1997).
o Resilience and performance over time. History has shown that new
technology does little good if it breaks down or becomes rapidly obsolete.
In such a condition the embodied energy of its production can easily
exceed any savings from its introduction. So too, buildings need to be
able to adapt to new uses, while remaining durable and easy to repair and
maintain. There is also evidence to suggest that buildings that reflect local
identity and “naturalness” are more likely to be found appealing and
worthy of care. (Allen, 2001).
Thus, although much more research is badly needed, and this overview is exceedingly
limited, the research on urban systems is already painting a remarkably clear picture:
denser, more compact, more walkable, more transit-served cities use dramatically less
energy per capita, when adjusted for other factors.
What is the magnitude of the reduction available from urban systems design, and what is
its percentage of the totality of energy use? Specifically, what is the magnitude of
overall reductions available assuming we could move from high energy-using urban and
suburban areas, such as those common in the US, to lower energy-using urban areas, such
as those more common in Europe and Asia? Bearing in mind that the factors vary
greatly, we can identify potential magnitudes of variations in the following key
components:
Transportation. We have seen that the energy used in transportation per person can vary
by as much as a factor of four. In the US, our model of high energy-using urban systems,
energy for personal transportation is in the range of 62% of all transportation energy.
(U.S. Environmental Protection Agency, 2005. Inventory of U.S. Greenhouse Gas
Emissions and Sinks: 1990–2003. Washington, DC, Table 2-9.) Transportation itself is
approx. 27% of all energy use. (Ibid.) Thus energy from personal transportation in the
US is approx. 16.7% of all energy.
It follows that a wholesale move (the most ambitious possible scenario) from a US highenergy model to a model based on more compact, transit-served urbanism, could produce
a reduction of up to three-quarters, or on the order of as much as a 12% reduction in
overall energy use.
Embodied energy. As noted previously, “tailpipe energy” is perhaps only about 2/3 of
total energy used by vehicles, including production energy, extraction and refinement of
fuels, pavement and other transportation infrastructure, and other embodied energy.
Following the logic above, this might be expected to add a savings of as much as 6%.
Other embodied energy in infrastructure includes power, water and other utilities, and
their construction. (Summarised in Hydro-Québec, 2005.)
The influence of building type. According to US Department of Energy research, multifamily homes in buildings with 5 or more units, the prevailing typology in higher-density
areas, use approximately 40% of the energy used by single-family detached homes, the
prevailing home type in low-density sprawl – a savings of 60%. (Energy Information
Administration (2005) Residential Energy Consumption Surveys, 1991-2005.) Since US
residential energy use is over 20% of all energy use, a complete change in building type
for a hypothetical 50% of all housing stock could represent a maximum possible savings
of up to 6% of all energy used. (Energy Information Administration (2005) Residential
Energy Consumption Surveys, 1991-2005
Opportunities for cogeneration and district energy. A study by Eliot Allen of Criterion
Planners, Portland, Oregon, suggests that these features can achieve energy savings of
25% or more in building energy consumption. (Allen et al., 2004) Again, residential
buildings in the US consume over 20% of all energy, meaning that such features could
achieve a maximum savings of 5% over high-energy urban areas.
Savings in transmission losses, leakage and other infrastructure efficiencies.
Transmission losses can represent 7% or more of all electric power generated (US
Cliimate Change Technology Program, 2003). A significant percentage of transmission
loss can be attributed to dispersed users, requiring longer and more dispersed lines.
(Dong, 2006) A similar impact occurs with leakage of water and other utilities,
requiring additional energy use. Electricity generation is approximately 40% of all
energy produced (Environmental Information Administration (2008). See e.g. Data
Table F1, 2008). Thus, a 25% reduction in transmission losses would amount to a
savings of 0.7% of all energy use. Savings from reduced leakage of water and other
utilities is likely to add small but significant quantities to these savings.
Behavioral and lifestyle factors. These have proven difficult to quantify, but anecdotal
evidence suggests they are major variables. Those living in higher-density urban areas
seem to spend more time in low-energy activities and consumption patterns. Those who
begin to use and enjoy some low-energy urban systems seem to increase their use of
those and other systems over time. (Podobnik, 2005, 2009) At present we are unable to
assign a specific reduction potential to these factors, but we believe it is plausible to
estimate a one to two percent savings.
Summary. Thus, the combined possible reductions in total energy use outlined above
may well be on the order of one-third of total global energy usage at present. This is
certainly an attention-getting magnitude. Of course, it must be added that this is an
optimum estimate figure. It does not reflect the fact that existing neighbourhoods would
likely remain at or near their current energy levels until they can be redeveloped or
significantly retrofitted. The actual realistic achievement from such strategies on a global
level may be perhaps half of this. Nonetheless, we suggest this is a dramatic and
important target for reductions in energy use.
This is a particularly important finding for areas of new urban growth, which are
common in the developing world. Given the pattern of American-style sprawl that is still
common (see illustration), this growth is likely to increase overall emissions even further
without dramatic changes.
But such systemic, thoroughgoing changes in urban form, in combination with more
efficient equipment, building retrofits, renewable energy sources and the like, begin to
point the way to more dramatic reductions in energy use, with similar opportunities to
reduce greenhouse gas emissions.
Current patterns of urban growth in the developing world, using McDonald’s as a proxy for other very
similar development now under way in these countries.
Strategies to Achieve the Available Reductions
Urban form develops slowly, and for this reason it often escapes the attention of those
looking for rapid energy reductions. Yet the corollary is that urban form is a persistent
energy user, and therefore any changes made now are likely to have a large and
compounding effect over time. This is particularly important in the developing world,
where urban growth is often dramatic and chaotic, and its impacts are set to shape global
energy and carbon patterns for many decades to come.
Research is continuing into a number of tools to produce more compact, transit-served,
walkable urban form. They range from age-old strategies (urban codes and regulations)
to innovative strategies (incentives, certification systems). Following is a summary.
Urban codes. Such codes have existed for many centuries, and are associated with many
of the best loved urban spaces (a famous example is Siena, Italy). So-called Euclidean
Zoning codes have been largely responsible for the automobile-dominated, segregated
development patterns of post-war sprawl. Recent innovations include form-based codes,
which prescribe urban form that supports walking and transit. Transect-based codes such
as the “SmartCode” combine form-based coding with categorization of regions into
“Transect zones,” with appropriate features form the highest densities to the lower
densities that will still prevail in agricultural communities and other more remote
locations. (See.e.g Talen, 2009, The Codes Project.)
Other regulations and prohibitions. These familiar tools include land use regulations,
such as urban growth boundaries, and prohibition of certain uses in certain locations. The
UK prohibition of “out of town shopping” is an example. The goal is often to eliminate
sources of high-energy and high-carbon activity, while leaving more desirable areas (such
as inner-city locations) to attract development. Critics often charge that such strategies
are cumbersome and often produce unintended consequences. Defenders respond that
previous regulations actually encouraged inefficient patterns, and a new generation of
regulations is needed now to correct the problem.
Plans and frameworks. Again, these are familiar tools, but new strategies are being
incorporated. One is to target areas for transit and transit-oriented development. Another
is to designate existing lower-energy and lower-carbon areas for protection and
enhancement. Criterion Planners of Portland, Oregon has a planning tool to identify
“cool spots”, as the most likely areas for lower-energy and carbon development (Allen,
2009).
Certification systems. These innovations generally provide a scoring matrix that gives
points for factors discussed herein, such as density, mixed use, walkability, access to
transit, and building type. The certification is a standard that developers and
municipalities can use as a promotional tool. In some cases governments will use such
systems to select preferred projects or to expedite approval – or in some cases, will apply
them as outright regulatory codes. In the US the new LEED-ND system (Leadership in
Energy and Environmental Design – Neighborhood Development) is attracting
widespread interest. In Europe the BREEAM system is prominent, but there are dozens
of other proposed systems at present.
Catalyst projects. These are projects deliberately created to trigger associated growth by
others. Often these are public projects, or public-private projects. Examples are transitoriented developments, model communities such as the UK’s “Eco-towns”, and
government development projects in preferred locations.
Pricing signals. These include taxes, tolls, fees, surcharges, credits, deductions, offsets
and the like. The economics of urban development may be thought of as its “operating
system”, and evidence shows it is a system that is highly sensitive to cost differences.
We know that motorists will choose to take transit when the cost of driving is increased
with road tolls, parking fees and the like. Development patterns will change when the
structure of costs and fees changes. Energy efficiency will increase as the cost of energy
increases, through market processes, but also through carbon taxes and the like.
Other incentives. These may include award schemes, grants, education and public
relation campaigns, policy reports and conclusions, research dissemination, and other
non-pricing influences. These are increasingly recognised as important but previously
under-appreciated contributors to decision-making.
Self-organisation management strategies. Although formal urban planning gets the
most attention, the fact remains that most urban structures are made by many agents
working to follow relatively simple rules in emergent collaborations. Biological science
has Recent research has demonstrated that many of the most optimal urban structures
have been made in this way as well. (Hillier, 2005; Batty, 2003.) Much productive
research is being done in this area, to understand how such emergent and self-organising
processes occur, and how we can exploit them to achieve more optimum urban
performance. In many cases the strategies involve employing the tools discussed above,
but doing so in a strategic way, taking a “systems approach”. This requires a different
strategy for analyzing urban problems, and for understanding and managing “the kind of
problem a city is,” in the famous words of the urban scholar Jane Jacobs.
“Toolkits.” Different cities and regions may find that different mixes of strategies work
most effectively, or are most feasible within varying political and cultural contexts.
Therefore it is important to offer a range of tools and strategies, and to allow local
citizens to adapt them to fit. In California, the Local Government Commission (LGC),
Congress for the New Urbanism (CNU), and Governor’s Office of Policy Research
(OPR) have proposed a series of “charrettes” or community workshops to develop and
apply custom tools and strategies to meet the statewide mandate for carbon reduction
under California’s landmark AB32 and SB375 greenhouse gas reduction legislation. This
and other jurisdictions around the world can be thought of as the “laboratories” where
effective new approaches will be developed, and it is vital that they have good research at
their disposal.
Conclusion: Policy Implications
We have seen that cities and suburbs are energy-using systems in their own right, and that
they can use energy in dramatically more or less efficient ways. Moreover, because they
tend to develop slowly, their structure can have a disproportionately large effect over
time – but at the same time, they may escape the attention of those seeking rapid
reductions.
This finding has important implications for policy to mitigate greenhouse gas emissions
effectively. Put simply, cities and their form will necessarily be a major variable in any
effective long-term mitigation strategy. The issue is particularly urgent, given the major
construction of infrastructure now under way in developing countries, which is set to
greatly affect emissions for many decades to come.
Yet in an indication of the challenge, recent debate in the USA, for example, has focused
on economic stimulus spending on reconstruction of existing (in some cases low-density)
transportation infrastructure. Many commentators have argued that this short-term focus
has come at the expense of another stated long-term goal: the mitigation of climate
change, through a new generation of economically viable low-E infrastructure. For some
observers, this is a reflection of a major and persistent policy “disconnect” between shortterm economic goals, on the one hand, and long-term environmental goals on the other –
but goals on which future economic viability clearly depends.
The reasons for this disconnect are understandable. As we have noted, urban systems are
highly complex, and it is difficult to tease out the many factors that contribute to their
behaviors. It is also difficult to identify our leverage over these factors, and for those
factors with high leverage, the mix of policy tools that can effectively manage these
morphologies, where more conventional top-down planning methods have proved
inadequate. Lastly, it is exceedingly difficult to marshal the political will to implement
the necessary policies -- in the USA and elsewhere -- as recent history has sadly
demonstrated. The new administration in the USA has shown that it has accumulated a
great deal of political capital, but also that it is going to be parsimonious with that capital
in its early months.
Yet as a number of investigators have noted, such systems issues are precisely the sorts of
challenges that must be met for an effective global response to the crisis of climate
change. The problem is not a narrow technical one, but a broad, systemic and political
one. It is precisely those systems that are complex, interactive, and collective that must
be managed successfully. For researchers, this means identifying both the factors that
affect emissions, and the tools that can manage them, in a politically feasible
environment. This is a daunting challenge, but a most necessary one.
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