ELSEVIER
M A N A G I N G U R B A N SUSTAINABILITY:
A N INTRODUCTION TO THE
SPECIAL ISSUE
Marina Alberti*
Stanford University
Lawrence Susskind
Massachusetts Institute of Technology
The impact of cities on the environment increasingly dominates the debate
on sustainability. Most global and regional environmental problems originate in cities. Cities concentrate increasing numbers of people and human
activities; thus, they import increasing amounts of natural resources and
export vast quantities of emissions and waste. Urbanization also entails
major changes in the way people use natural resources. While it accelerates
the transition from traditional to modern fuels, it also intensifies the use
of energy and its environmental impacts. Indeed, a nation's levels of energy
use and greenhouse emissions are both positively correlated with its urbanization level (Jones 1991; Hosier et al. 1993; Parikh and Shukla 1995). On
the other hand, cities provide major opportunities to achieve economies
of scale and use natural resources more efficiently. Compact urban settlements, for example, are generally more energy efficient than dispersed ones
(Owens 1986; Newman and Kenworthy 1989, 1990; Lowe 1991; Gilbert
1992). Thus, the way cities are designed and managed can be crucial to sustainability.
This special issue addresses two questions: What makes a city sustainable?
A n d what strategies can urban managers adopt to achieve greater sustainability? What makes urban settings especially interesting is that cities
are organized systems of many interacting biophysical and socioeconomic
components and that the way they are organized and managed affects the
level of environmental pressure that individuals exert. Whether a city's
inhabitants choose a private or public transportation system to commute
between home and work depends among other considerations on the avail* Marina Alberti edited this special issue while at the Center for Conservation Biology of Stanford
University. She has recently joined the Faculty of the Department of Urban Design and Planning at the
University of Washington.
Address requests for reprints to: Dr. Marina Alberti, Department of Urban Design and Planning,
University of Washington, Gould Hall, 410H, Box 355740, Seattle, WA 98195.
ENVIRON IMPACT ASSESS REV 1996;16:213-221
© 1996 Elsevier Science Inc.
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ability of an efficient public transportation system. This, in turn, hinges on
the implementation of numerous collective decisions to manage urban
growth and invest in public transportation (Alberti, this issue).
To investigate these questions, we start by defining sustainability. The
term is used in ecology to indicate a condition that can be maintained
indefinitely without progressive diminution of quality (Holdren et al., 1995).
Applied to economic development, sustainability implies maintaining the
capacity of natural ecosystems to support the human population over the
long term. There are, however, various interpretations and much discussion
about what should be sustained and for how long. One major disagreement
is over whether economic growth is compatible with maintaining natural
capital. On one extreme are those who argue that trade-offs between economic growth and environmental protection might not be necessary (Colby
1990; Pezzey 1992; Solow 1992). Those on the other side stress that these
forces inevitably clash (Daly 1989; Shiva 1992). Arrow et al. (1995) hold
that what decides whether they are compatible is the content or composition
of growth.
An even greater challenge is understanding what sustainability entails
in practice. We currently know little about the sustainability of the various
paths taken by modern developed and developing economies. In practical
terms, sustainability is also hard to generalize. Distinct development trajectories in different countries suggest that no single strategy, however sustainable, will apply equally in all countries. Patterns of resource use are mediated by each nation's economy, environment, and culture. In the
postscriptum to this special issue, William Moomaw of Tufts University,
stresses that for urban society it is culture that shapes the relationship
between the economy and the environment.
Whatever the most compelling definition, certain common elements of
sustainability are relevant whether we are in the North or the South, in
the private or public sector, or working at the global or the local level. We
suggest four general propositions:
• Sustainability requires invention, not just discovery. Knowledge of
how the global environment works and how human development interacts
with it are essential, but must account in each instance for people's perceptions and values. There are no universal rules that can be applied to all
contexts at all times. Instead, sustainability needs to be reinvented continually. All parties involved must learn how to work together to set sustainability goals and develop strategies to meet them.
• Sustainability is an opportunity rather than a constraint. Only when
all parties recognize the common benefits of meeting everybody's needs
and aspirations will we generate the capacity to maintain natural capital
over the long term. Indeed, to achieve sustainability, all parties involved
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must commit themselves to meeting the needs of both present and future generations.
• Sustainability is a process, not an outcome. In the words of the Burtland Report: "Sustainability is not a fixed state of harmony, but rather a
process of change, in which the exploitation of natural resources, the direction of investments, the orientation of technological development, and
institutional change are made consistent with future as well as with present
needs" ( W C E D 1987). The process involves trade-offs among contending
groups with different interests, priorities, and perceptions in the face of
controversial scientific evidence.
• Sustainability involves a self-conscious choice; it does not simply happen. Sustainability requires leadership. Local and national governments--in
partnership with the private sector and nongovernmental organizations-need to work together to meet their global responsibilities.
These propositions can help to operationalize the management of urban
sustainability. For cities, the notion of sustainable development extends
their borders and their responsibility for the impact they have on the global
commons. This entails local decision-makers considering global environmental impacts when making the trade-offs. Cities need to recognize
• the needs of all people, not just those within their boundaries and
present as well as future generations; and
• the finite limits on certain resources and on the capacity of the local,
regional, and global settings to absorb the pressure of human activities.
The articles in the first section of this volume examine the issues as well
as describe the actors and interests at the urban scale involved in achieving
sustainability. The definition of urban sustainability raises several questions
about how to set certain thresholds for city development. We argue that
the actors and interests involved in each instance are central to answering
these questions. The articles in the second section examine how best to
integrate concerns about sustainability into urban decision-making---What
regulatory mechanisms, economic incentives, and voluntary actions are
important? Through what planning processes can cities be responsive to
both local and global environmental considerations?
The second United Nations Conference on H u m a n Settlements (Habitat
II) held in Istanbul in June 1996 highlighted the need to work collaboratively
to integrate priorities at the local and global scales. The issue of "adequate
shelter for all" and "sustainable human settlement" opened up a new series
of controversies within and across the 171 participating countries. In a
third section, we invite Michael Cohen, a Senior Expert on sustainable
development at the World Bank, Enrique Ortiz, of Habitat International
Coalition, and Rafael Greca de Macedo Mayor of Curitiba in Brazil to
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give their perspectives on the Conference and the Habitat Agenda adopted
in Istanbul. Finally, we suggest possible directions for future research on
urban sustainability.
What Are the Issues?
The next few years will mark a shift from a predominantly rural to a
predominantly urban world. By the year 2000, 45% of the population of
developing countries (1.97 billion) and 75% of the developed world (945
million) will live in cities. With an annual rate of increase estimated at
2.5%, by 2025, the urban population is expected to reach 5.5 billion: the
current total world population. The urban population in developing countries will reach 4.3 billion inhabitants: more than three times the urban
population of developed countries, which is projected to be 1.2 billion. The
environmental and social impacts of this rapid urbanization constitute what
we believe is the most important challenge for the management of sustainability.
In developing countries, urbanization occurs so rapidly that it typically
overburdens the ability of local governments to provide adequate housing,
infrastructure, and other essential services. In 1950 Lagos had 288,000
inhabitants. Today it has 8 million inhabitants and is expected to double
in size in the next decade. At present, more than one-third of the world's
urban residents live in substandard housing and at least 250 million people
have no access to safe water. Often, the absence or poor management of
basic infrastructure negatively impacts the local and global environment.
On the other hand, as income levels and industrialization increase, so do
the environmental pressures created by urban activities.
In the developed world, already highly urbanized, the process of suburbanization is the key challenge to local governments trying to provide
a sustainable environment. Most of the cities that have improved local
environmental conditions are now facing new environmental problems.
Indeed, while fuel substitution, combined with strict regulation, have dramatically reduced the emission of sulfur dioxide and particulates from
domestic heating, refineries, and power plants, there is increasing concern
about traffic-generated pollutants such as particulates, nitrogen oxides, and
carbon dioxide. In Los Angeles, sulfur dioxide and lead have been significantly reduced, but particulate matter, carbon monoxide, and ozone are
still significant problems. Urban traffic in the cities of the developed world
is expected to grow, following transportation trends, and suburbanization
patterns, making matters worse.
The first section of the special issue examines the evolution of urban
environmental problems in the developed and developing world and the
role that cities must play to achieve sustainable development. Despite the
increasing number of scholars and institutions looking at these issues, the
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relationship between economic development and urban environmental performance is still not well understood. Estimates by the World Bank (1992)
show that urban concentrations of sulphur dioxide and particulates increase
as income rises and then decline. Such relationships have been described
by so-called Kuznet curves (inverted U-shaped curves) (Grossman and
Krueger 1994). However, other environmental indicators worsen as income
rises: per capita generation of solid waste, nitrogen oxides, and carbon
dioxide emissions. This suggests that as income increases, urban environmental problems tend to shift from the local to the global (Alberti and
Layton 1996).
In this issue, scholars address the linkages between local and global
sustainability by focusing on the use of natural resources, energy, transportation and land use, and public health.
Urban Impact
William Rees, of the University of British Columbia and Mathis Wackernagel, of Universidad Anahuac de Xalapa in Mexico, introduce the concept
of urban ecological footprint--the aggregated area functionally required to
support a given city's activities. This concept captures the relationship
between local and global sustainability. Since cities increasingly depend on
natural resources of vast regions, achieving local sustainability does not
ensure their global sustainability. Cities may improve local environmental
conditions in the short term by placing unsustainable demands on natural
resources elsewhere and exporting their emissions and waste to other regions. The interdependence between local and global sustainability become
evident when urbanization is viewed from a long-term perspective. Indeed,
these same cities will be affected by the consequences of global environmental problems such as climate change, acidification, and stratospheric
ozone depletion.
Urban Energy
The impact of urban energy demand on the local and global environment
depends both on total demands from urban activities, end uses, and fuel
mix. The contribution of the transportation sector to urban energy consumption is increasing in cities as a result of decentralization. Since energy use
is most concentrated within cities, local actions to increase energy efficiency
and introduce clean alternative energy sources are critical both to reduce
global impact and improve the quality of life at the local level. Ariel Alexander, ex-Director of the Organization for Economic Cooperation and Development (OECD), Urban Affairs Division of the Environmental Directorate, and Nicola De Michelis, currently a consultant on these issues at the
European Commission, examine current approaches to achieving energy
efficiency and CO2 reductions in OECD cities.
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Urban Transportation
Cities will increasingly have an impact on the environment because of
their dependence on the automobile. Traffic-generated pollutants such as
particulates, nitrogen oxide, and carbon dioxide are an increasing problem
as cities sprawl. Photochemical smog is a serious threat in most cities. Lead
poisoning is an increasing concern, particularly in large agglomerations of
the South. Urban traffic also causes increased noise and congestion. Jeffrey
Kenworthy and Felix Laube from Murdoch University in Australia, examine some of the underlying land use, transport and economic reasons for
these different transport patterns in cities across various regions. They
review strategies to achieve sustainability through land use planning and
transport management.
Urban Health
Urbanization leads to important changes in the way people live. It is no
surprise that urban growth can affect the health of a population due to the
increased access to health services in urban areas as well as to increased
environmental threats in cities. Urbanization also exacerbates the unequal
distribution of resources with important consequences for people's health.
Trevor Hancock, professor of public health at York University in Canada,
examines the links between health and urban sustainability. He discusses
the principles underlying the Healthy Cities Project which the World Health
Organization has established in many cities to promote health improvements through the upgrading of physical and social environments.
The Management of Sustainability
In the second section of the special issue, several authors focus on how
local and international agencies can promote urban sustainability. Chapter
28 of Agenda 21 includes a mandate for all local authorities to prepare a
local Agenda 21. It stipulates that "by 1996, most local authorities in each
country should have undertaken a consultative process with their population and achieved a consensus on a local Agenda 21 for the communities."
Many cities have developed just such chapters to coordinate local government efforts to enhance sustainability. Various approaches to setting priorities, assessing development options, building institutional capacity, and
measuring success are examined.
Setting Priorities
Cities need to make critical choices about what issues to give priority.
Pursuing a broad consensus among all actors involved is usually necessary
for success. Pratibha Mehta, Director of the Local Agenda 21 Model Communities Program, assesses the lessons learned thus far in setting local
agendas and implementing sustainable urban strategies in Africa, Asia,
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and Latin America. The Program is an international initiative aimed at
supporting a selected group of municipalities to design, test, and evaluate
planning frameworks for sustainable development.
Assessing Options
The theory and practice of Environmental Impact Assessment (EIA) can
help to operationalize sustainability at the urban scale. E I A is an essential
tool for assessing the impact of alternative development strategies. Anne
Shepherd, of the City Planning Program at Georgia Tech, and Leonard
Ortolano, Director of the Urban Studies Program at Stanford University,
examine the opportunities and constraints that E I A creates for achieving
urban sustainability goals. They argue that the concepts of areawide E I A
and cumulative impact assessment are crucial for setting and achieving
sustainability targets.
Building Institutional Capacity
Despite their efforts to achieve sustainability, many cities lack the power
or the financial resources needed to choose development paths that respond
to local needs and aspirations. This is especially true in developing urban
economies dependent on international markets and financial strategies.
Local and international actors can help to build capacity to improve urban
environmental performance. Joseph Leitmann from the World Bank examines the lessons learned at the Bank through investments in urban infrastructure in developing countries. Jeb Brugman, Director of the International
Council for Local Environmental Initiatives, discusses the role of cities as
partners in solving global environmental problems.
Measuring Success
A key question for local and national policymakers is how to measure
success. What set of indicators can help to chart city efforts to achieve
greater sustainability? The question is how to select a few measures that
can provide urban managers with clear signals. Marina Alberti, of Stanford
University, examines O E C D , United Nations, and World Bank proposals
regarding the selection of a set of urban indicators as well as a few examples
at the regional and local scales. Alberti holds that a set of widely accepted
urban sustainability indicators can be crucial to influencing both decision
makers and public attitude. Alan AtKisson, a p r o m o t e r of the communitybased initiative, Sustainable Seattle, focuses on lessons that can be drawn
from the process of developing sustainability indicators for Seattle.
A Research Agenda
Urban sustainability requires new definitions. To date, no universally accepted definition brings together a synthetic measure of sustainability. Dif-
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ferent approaches focus on varying components of the urban environment
or on the various functions of urban systems missing important linkages.
One research question that requires special attention is the relationship
between environmental quality and human health in the city.
There is also urgent need to implement systematic monitoring of activities
and impacts at the urban scale. Indeed, while data about air pollution
concentrations are often available for local policy making, levels of urban
energy consumption or CO2 emissions--more relevant to global policy
making--are rarely collected at the local scale. Even when data do exist,
they are often collected by different agencies with very different needs and
methods. A common and restricted set of urban environmental indicators
needs to be developed to help local and national policy makers improve
their efforts to manage for greater sustainability.
In addition, further research is necessary to ensure that new available
information feeds back into urban decisionmaking. What regulatory, economic, and voluntary mechanisms will make sustainability part of everyday
decisionmaking? And, what planning process will best facilitate the development and implementation of such mechanisms?
Finally, the discussion in this issue highlights a number of questions that
urban planning theory has not addressed. Although there is a growing
consensus that cities may contribute to solving global environmental problems, little evidence has been provided demonstrating the impact of alternative urban patterns on urban environmental performance. Interventions
aimed at reducing the adverse environmental impacts of urbanization depend on new insights regarding these interactions.
The editors wish to thank all the authors for their contribution and for their patience with
the difficult process in preparing a special issue. Theresa Hill, editor of the EIA Review
provided invaluable assistance at all stages of this project. We are also grateful to the Center
for Conservation Biology (CCB) at Stanford University and particularly to Carol Boggs for
her support and encouragement. The generous support of the Koret Foundation and an
anonymous donor made this project possible. We also wish to thank all participants of CCB
Policy Forum at Stanford University and particularly to Paul Ehrlich, Gretchen Daily, David
Layton, Michael Dalton, and Jennifer Hughes for their support and ideas. We are grateful
to Stephen Boyden (Australian University), fan Clark (European Commission, Directorate
General XI), and Angela Liberatore (European Commission, Directorate General XII) for
their useful comments at an early stage of this project; David Stanners (EEA, Copenhagen)
and Joe Flood (UNCHS, Nairobi), and Birgitte Bryld (UN DPSCD, New York) for the
information on indicators; Ricardo Cleon dos Santos (Universidade Livre do Meio Ambiente)
for the interview with the Mayor of Curitiba; and Helen Snively for editorial assistance. A
special thanks also to the participants of the EcoCity Conference, Dakar, Senegal (January
1996).
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