January 21, 2015

Expert Voices 2015: Will the Battle for Sustainability be Won or Lost in Cities?

By: Penn IUR Faculty Fellows and Scholars

The world’s urban population is growing rapidly, and this population will present significant challenges for global cities in the coming decades. While 54 percent of the world’s population lives in urban areas today, that number is projected to jump to 66 percent by 2050.  So how can our cities keep pace? How can they expand sustainably to absorb this massive population increase? For our annual roundup of expert voices this year, we asked a panel of urban experts to weigh in on how cities factor into global efforts to make the world a more sustainable place. In particular, we asked our experts to consider this question of sustainability in the context of the United Nations’ Sustainable Development Goals (SDGs), universally applicable goals that will drive the implementation of sustainable development on a global scale.

Within a year, the UN General Assembly will adopt a set of Sustainable Development Goals (SDGs). The working group tasked with formulating the SDGs has proposed potential goals, and of particular note for urbanists is the one that reads: “Make cities and human settlements inclusive, safe, resilient and sustainable,” accompanied by seven targets related to spatial issues and assembled to present an integrated (not sectorial) approach to building or rebuilding communities: planning, housing, transport, public space, environmental impact (air pollution and solid waste), cultural heritage and disaster preparedness. Some people think that a stand-alone goal on cities and human settlements is not necessary as other goals will cover the matter while others say the other goals neither pay attention to integrating the elements like housing, transportation and environment nor consider the physical or spatial design of cities and human settlements. 

In light of this, we asked our experts:

As we look ahead to 2015 and beyond, in your opinion, how important are these urban-related targets for the broader goal of urban sustainability? Choose a target or targets, or feel free to comment on the overall process of finding a place for cities in the UN’s SDGs or the overall issue of urban sustainability. Do you think the battle for sustainability be won or lost in cities? 

Eugenie Birch and Susan Wachter | How Should We Think About the SDG’s…Especially the One on Cities?

Solly Angel and Alex Blei | A Need for Systematic Evidence on the Quality of Urban Expansion

Robert Buckley| Little Hope for an Urban-Focused SDG in 2015

Marc L. Imhoff | Sustainability Goals and the Urban Enterprise 

Stephen Malpezzi | Highly Imperfect Goals, But Important Tools for Reform

Susan Parnell | Dedicated Emphasis on Cities is Itself Huge Progress

Andrew Rudd | Cities are an Integral Part of the Solution

Karen C. Seto | The Time is Now for Leadership from the UN

Christopher Small | Goals and Outcomes

Marilyn S. Sommers | Global Traffic Risks for Women and Children: The City is the Key

Richard Weller | BiodiverCity


How Should We Think About the SDG’s…Especially the One on Cities?

Eugenie Birch and Susan Wachter are Co-Directors of the Penn Institute for Urban Research. Birch is Lawrence C. Nussdorf Professor of Urban Research and Education and Chair of the Graduate Group in City and Regional Planning. Wachter is Albert Sussman Professor of Real Estate and Professor of Finance at the Wharton School.

Through their signatures on the 49th page of The Future We Want, the Rio+20 outcome document, 192 nations offered global agreement to create SDG goals aimed at two objectives: “to eradicate poverty” and “to achieve development within planetary boundaries.” The nations concurred that such goals would be universal and, at the same time, aspirational and achievable, a seemingly impossible quest in the face of greatly varying stages of worldwide development. Likely, they believed that they were either forging an approach that would promote shared interests or one that would avoid common risks or misfortunes or some combination of the two.

We propose that one way of making sense of the directives, especially the mandate to forge Sustainable Development Goals for urban-focused researchers is to base their understanding on the following two assumptions: 1. The SDGs can offer a coherent structure for framing approaches and identifying critical drivers of the desired outcomes of the two purposes but they cannot prescribe in detail solutions best left to individual nations; and 2. The SDGs can offer a platform for experimentation and learning to shape implementation strategies based on multi-scalar public and private decision-making that will play out in physical space –in other words, place matters.  

While we did not specify these considerations when we asked a range of experts to gauge the potential effects of the proposed SDG goal on cities and human settlements, the reader will see that responses point in these directions. They demonstrate each respondent’s disciplinary and experiential background. Taken together this dialogue not only illuminates the complex policy issues related to sustainable development but also underlines the necessity of engaging many disciplines in addressing them and the need to find a simple common theme to organize productive and action-oriented thinking (in this case cities and human settlements). 

Here, we suggest that cities and human settlements, with their demographic, economic and environmental heft and impacts, serve as the crucible for sustainable development. In particular, we call for a focus on land and its treatment at multiple scales to serve as a critical organizing principle for crafting implementation strategies that will, at a very minimum, create the needed conditions that permit individuals to live healthy, economically-viable and socially-inclusive lives, as well as permit the earth to offer the underlying natural resources that will make this aspiration possible.

Framing urban issues around land and its disposition shouts out for engaging in dialogue with many of the disciplines represented in the contributions below. With the economists, we can discuss how to inject issues of institutional, financial and regulatory capacity and the delivery of public goods. With the designers we can discuss what arrangements within and outside of urban boundaries will offer the provision of a range of public goods from space for safe streets to room for ecosystem services. With the physical scientists, we can explore planetary sustainability – a world in which all people have access to water, food and energy.  In this manner, urban researchers can contribute to adding coherence and new knowledge to the grand objectives of the Sustainable Development Goals.

A Need for Systematic Evidence on the Quality of Urban Expansion

Solly Angel is Senior Research Scholar, NYU Stern Urbanization Project and Alex Blei is Non-resident Research Scholar, NYU Stern Urbanization Project, New York University.

Between 2000 and 2050, the urban population in developed countries will increase by 160 million. The urban population of developing countries is expected to increase by 2.5 billion, 16 times that of developed countries. Urbanization is now a developing-country issue. One-third of the 4,000+ cities that had 100,000 people or more in 2010 are now growing at 3% per annum or more. These cities—all in developing countries—are likely to triple their populations by 2050. We can do very little to curb urban population growth, but we can certainly prepare adequate lands in these cities to accommodate that growth.

Stated as a broad policy goal, rapidly-growing cities need adequate lands to accommodate their growing populations, and these lands need to be properly serviced and yet affordable to be of optimum use to their inhabitants. Cities that can consistently meet this goal become more efficient, more productive, more equitable, more sustainable, and more resilient. And to meet this goal they need concerted public action, action that must precede and guide the operations of the free market on the urban fringe. In the absence of concerted public action—action that can secure adequate lands for public works, public open spaces, and public facilities in advance of development—land and housing markets, efficient as they may be in theory, will fail to perform properly in practice.

We have the beginning of a scientific understanding of the quantitative aspect of global urban expansion. However, there is only anecdotal evidence regarding the quality of global urban expansion. Systematic evidence on the quality of urban expansion is now needed to make the case for cities the world over to become proactive in making adequate preparations for their inevitable expansion.

Little Hope for an Urban-Focused SDG in 2015

Robert Buckley is Senior Fellow, International Affairs, Milano School of International Affairs, Management and Urban Policy, The New School.

In principle an urban-related goal or goals is an excellent idea.  It is one that is likely to inevitably be adopted.  However, it will almost certainly not take place in 2015.  We will probably need an “urban crisis” of some sort before adequate attention is paid to the effects cities have on development processes.  I take this pessimistic view for three reasons:

  • First, the expert document prepared for the UN deliberations does not mention urbanization as one of the key underlying trends that will shape the future, even though in the next hundred years urban populations will triple and most of that will be in the cities of some of the poorest countries;
  • Second, the UN’s rhetoric itself is partially to blame.  It casts the “urban problem” as one of poverty and income distribution, and continues to do so in the run-up to Habitat III.  But, the urban problem is not one simply of poverty that requires yet greater redistribution of resources in a world seemingly plagued with fiscal concerns.  The problem is making sure the basis for growth – certainly more equitable growth – occurs.  In many cities of the developing world the existence of such platforms for sustainable growth is anything but a foregone conclusion.  The high return investments that would create these platforms are not being undertaken.  To give just one of many possible examples, the fact that cholera – a disease effectively banished from OECD countries in the 19th century—has been endemic in East Africa for more than 20 years reflects this failure.  Without such urban infrastructure investments not only will poverty increase it will be concentrated in cities of mass unemployment; and
  • Third, cities are essentially bundles of public goods.  Governing them is very hard to do and measuring that governance is even more difficult.  The Cities Alliance’s recently published measures of the effectiveness of urban governance in Sub-Saharan Africa is a major step forward – both in measurement as well as in detailing just how low is the quality of urban governance in most Sub-Saharan countries.  However, none of the proposed measures for urban social development concerns considers such governance.

Without better urban governance, provided by if not democratic then at least competitively accountable governance – as in China – cities will not be able to provide the networks that have always been the bases for innovation and hence are the wellspring of growth.  The world is already more than half urbanized.  As this share continues its relentless increase, it will finally be understood that the effectiveness with which this extremely productive share of the population is governed is essential.  The discussions of an urban goal so far have unfortunately missed this point.

Sustainability Goals and the Urban Enterprise 

Marc L. Imhoff, Earth System Science Interdisciplinary Center, University of Maryland.

As we begin to define our goals for a sustainable human enterprise (see UN SDG’s 2015-2030) it is inevitable that we turn our attention to the development, maintenance, and livability of our cities. The energy, food, water, and materials required to sustain the scale of our urban places require that we consider a suite of interconnected ecological, biophysical, and socio-economic factors that operate over different spatial and temporal scales and reach far beyond the urbanized footprint. In addition, other factors such as technology, policy, and changes in weather regimes, and other extreme events natural or otherwise, are powerful modulators in the performance of built environments.

In order to look forward and assess the possible responses to decisions we make now, an approach is required that connects the urban metabolism more directly with the sustaining suite of biophysical and socio-economic processes. Integrated assessment (IA) modeling, where the human and natural systems are fully coupled in a single model, represents one potential avenue to do this. However, most IA models currently do not define urbanization specifically, but rather obliquely through sectors that contain the various elements found there (e.g., energy and energy technology, transportation types, population, GDP, etc.).  As a result, while the global drivers affecting local conditions are maintained, it is difficult to interrogate the models for potential outcomes from an urban-centric viewpoint.

This is an important debate in modeling human-natural systems. Overlap in the sectoral representation within a model does not necessarily mean they can be readily adapted to address issues of direct relevance to urban sustainability. One worthwhile goal for the urban modeling community therefore is the development of IA models that are able to capture the spatial components of “clusters of sectors” that, in this case, represent urbanization. Such a “spatialization” effort if correctly embedded in the models would allow the flexibility of the IA approach retaining the global drivers across all sectors while enabling focused inquiry for studying outcomes on urban places explicitly. If successful, this approach would provide a valuable tool for scientists, planners, and investors to test approaches for creating sustainable cities and the urban sustainability targets described by the community.

Highly Imperfect Goals, But Important Tools for Reform

Stephen Malpezzi is Professor, Graaksamp Center for Real Estate, Wisconsin School of Business.

In 2000, 189 countries agreed to support a set of objectives called Millennium Development Goals with the aim of developing a set of goals with corresponding indicators.  A year later, the UN Secretary General unveiled a set of specific goals, The Millennium Development Goals (MDGs) for 2000-2015.

Over half the world’s population lives in cities; about 70 percent of global GDP is created there.  It’s also true that perhaps 80 percent of greenhouse gases are connected to cities; but improving the design and efficiency of cities presents some of the best opportunities to improve environmental outcomes (Birch 2014).  In a world with over half the world’s population living in cities, many of the goals, and their associated indicators have implications for and are affected by conditions in cities.  With respect to the MDGs, the explicit urban goal was Target 11, namely, “By 2020, to have achieved a significant improvement in the lives of at least 100 million slum dwellers.”

The MDG’s urban goals have been criticized on several grounds, including on the definition of “slums” (Angel 2005) and on the lack of sufficient ambition, given the scale of urbanization, and its contributions to development (Cohen 2014). The broader sets of MDGs, and their implementation, have, of course, been criticized as well.  See Easterly (2007), Fehlingha (2013) Friedman (2013), and Fukuda-Parr (2014).  Perhaps the most important critique is based on some good news.  Despite many qualifications and caveats that can be made, the past two decades has seen, on balance, a combination of policy reforms, institutional development, and resurgent markets in a number of countries (including but not limited to India and China, with almost 30 percent of the world’s population between them) that have yielded powerful growth in GDP, concomitant reductions in extreme poverty, and greater access to water, sanitation, health care, and other correlates of quality of life (Chen and Ravallion 2010).  The MDGs may have made some marginal contribution (see Friedman 2013 for a careful study that fails to find any significant effects), but I know of no serious claim that the MDG is the prime mover in these impressive improvements.

As of this writing a follow-on set of “Sustainable Development Goals” are under debate and discussion.[2] What, exactly, is meant by “sustainable?”  I think economists can contribute to the understanding of this oft-cited, rarely well-defined term.  A sustainable development path is one that, in Robert Solow’s phrase, preserves “our generalized capacity to create well-being.” 

Solow also notes what sustainability is not.  It is not conditional on a perceived supply of “any particular thing or any particular resource.”  That’s because economists focus, inter alia, on our ability to substitute one good or service for another, in response to changes in relative prices; that the feasible sets of production and consumption possibilities grow over time as incomes rise and technology evolves and spreads; and finally, that technological progress itself does not (often) fall out of the sky, but is usually itself endogenous. That is, when relative prices rise, signaling the increasing scarcity of a good or service, consumption adjusts; but incentives are also put into play that drives more R&D and entrepreneurial energy in that direction.

Currently, the Sustainable Development Goals are draft goals, and there are a lot of them.  They will no doubt be revised over the coming year.  More broadly, does creating a new set of Sustainable Development Goals have value, in general or for cities?  They’ll be highly imperfect, as their predecessor Millennium Development Goals were.  It can be argued that they will facilitate a conversation and provide a focal point.  Perhaps there’s a Hawthorne Effect at work.  By focusing on even highly imperfect goals, with even less perfect implementation, it can be argued that the increased attention of a wide range of actors could be salutary.   These issues have long interested aid agencies, NGOs, some governments, and some academics; but now we find new actors interested, including broader participation by the private sector.  One thing I’ve learned in a business school is that marketing does indeed matter.

The new SDGs will differ in several ways from the MDGs.  In addition to their broader scope, SDGs will apply, in principle, to all countries, not just developing countries/emerging markets that were the focus of the MDGs.

My own view is that the biggest shortcomings of the MDGs and the SDGs are that they focus so much on external aid and expertise.  This external aid and expertise can, I think, have positive effects on certain margins;[4] but in the end, progress in development must come from within.  A wide range of literature discusses this, both broadly (Acemoglu and Robinson; Easterly) and with respect to housing and urban development (Mayo, Malpezzi and Gross 1987; Malpezzi 1993).  Perhaps the most important contribution of the next round, of the “Sustainable Development Goals,” would be to foster debates and discussions that would get more countries, and the governments, firms, and citizens that comprise them, to buy into the continued policy reforms and development of institutions that will build on the progress of the past 30 years both in the countries that have been succeeding in important governance reform and those that have not yet done so.


Acemoglu, Daren, and James Robinson.  Why Nations Fail. 

Angel, Shlomo.  Defining and Monitoring Target 11: A Policy Note.  Mimeo, 2005.

Birch, Eugenie.  Sustainable Development Goals Should Aim to Make Cities Inclusive, Resilient, Safe and Livable.  October 2014. 

Chen, Shaohua and Martin Ravallion.  The Developing World is Poorer Than We Thought, But No Less Successful in the Fight Against Poverty.  Quarterly Journal of Economics, 2010.

Cohen, Michael A.  The City is missing in the Millennium Development Goals.  Paper prepared for The Power of Numbers: A Critical Review of MDG Targets for Human Development and Human Rights, 2013.

Easterly, William.  Can Foreign Aid Buy Growth?  Journal of Economic Perspectives, 2003.

Easterly, William.  How the Millennium Development Goals are Unfair to Africa.  Brookings Institution, 2007.

Fehlinga, Maya, Brett D. Nelson and Sridhar Venkatapuramd.  Limitations of the Millennium Development Goals: a Literature Review.  Global Public Health, 2013, 8(10), 1109–1122

Friedman, Howard Steven.  Causal Inference and the Millennium Development Goals (MDGs): Assessing Whether There Was an Acceleration in MDG Development Indicators Following the MDG Declaration.  Brookings Institution, 2013.

Fukuda-Parr, Sakiko, Alicia Ely Yamin and Joshua Greenstein. The Power of Numbers: A Critical Review of Millennium Development Goal Targets for Human Development and Human Rights,  Journal of Human Development and Capabilities, 2014

Malpezzi, Stephen.  Getting the Incentives Right: A Reply to Baken and Van Der Linden.  Third World Planning Review, 1993.

Mayo, Stephen K., Stephen Malpezzi and David J. Gross.  Shelter Strategies for the Urban Poor.  World Bank Research Observer, 1986.

McKinsey Global Institute.  Urban World: The Shifting Global Business Landscape.  2013.

McKinsey Global Institute.  Tackling the World’s Affordable Housing Challenge.  2014.

Merrett, Frank.  Reflections on the Hawthorne Effect.  Educational Psychology,         26(1), 2006.

Prahalad, C.K. The Fortune at the Bottom of the Pyramid.

Solow, Robert M.  Sustainability: An Economist’s Perspective.  J. Seward Johnson Lecture to the Marine Policy Center, woods Hole Oceanographic Institute, woods Hole, MA, June 14, 1991.

World Bank.  Urban Policy and Economic Development:  An Agenda for the 1990s.  Washington, D.C., 1991. 

World Bank (1993). Housing: Enabling Markets to Work. Washington D.C., World Bank.  Principal authors Stephen K. Mayo and Shlomo Angel.

Dedicated Emphasis on Cities is Itself Huge Progress

Susan Parnell is Professor, African Center for Cities, University of Cape Town.

Cities are simultaneously the most important new sites of development (already acting as host to more than half of the world’s population) and the most important hubs of social, ecological and environmental activity, where the impacts of new construction and urban consumption are always felt beyond the boundaries of the settlement. Because cities are the key drivers of global environmental change it follows that they must also be the focus of sustainable development intervention. Because cities have been shown to be the pathways to social, economic and ecological development it is appropriate that the global community endorse a dedicated urban goal in addition reporting on spatially differentiated progress on other sustainable development targets.

Making Goal 11 (the stand alone urban goal) a meaningful force in the push for sustainable development will not be easy. The goal and its targets are very ambitious. The dedicated focus on cities requires action from multiple scales of government and multidimensional interventions. Implicitly, Goal 11 introduces a sub national scale of intervention not hitherto an explicit part of the UN’s developmental focus. The goal is likely to generate both political and operational difficulty because, especially in the developing world, the necessary data is going to be very hard to identify and/or to relate in a causal manner to development interventions. Proposed targets will need critical assessment before they are accepted. The fact that cites (unlike health or education) is a new area of intervention, along with the complexity of forces that determine urban development outcomes, mean that Goal 11 is unlikely to meet all expectations. But, the fact that there will be a dedicated emphasis on cites is huge progress and this victory puts the onus on the urban community to maintain their involvement in the UN process and critically engage the post 2015 agenda.

Cities are an Integral Part of the Solution

Andrew Rudd is Urban Environment Officer, Urban Planning and Design Branch, UN-Habitat.

The battle for sustainable development will indeed be won or lost in cities. So will the achievement of the SDGs. In response to the 1968 riots in Paris, Henri Lefebvre essentially coined the phrase ‘the right to the city’ claiming that all social relations are mere hypotheses until they are spatialized. If that is true, then no social aspect of the SDGs will be realized without a focus on place and space. (And there are massive economic and environmental co-benefits as well.) For me the most critical targets are 11.3 (which addresses urban planning) and 11.7 (which addresses safe public space). These are the sine qua non of sustainable development in the 21st century. First, without spatial planning we will not manage to preserve periurban agricultural land and we will not win the battle for food security. Moreover, cities will not meet the minimum density thresholds required to sustain public transport and the battle for sustainable transport will also be lost.

Second, without public space we will lose the battle to extend basic services to all, because without rights-of-way there can be no streets, no pipes and no sewers. Third, without aligning the two—planning at the metropolitan scale, design at the scale of the neighborhood—we will not get the home-work-services triangle right so that people occupy housing within a reasonable commute of decent employment. Nor will we be able to build the kind of shared infrastructure that lowers per capita rates of resource use and builds resilience against future shocks. We desperately need to win each of these battles. And victory is within reach— but only if we see cities as an integral part of the solution.

The Time is Now for Leadership from the UN

Karen C. Seto is Associate Dean of Research; Professor of Geography and Urbanization; Director of Doctoral Studies, Yale University School of Forestry and Environmental Studies.

One of the primary objectives of the UN is to achieve “international cooperation in solving international problems of economic, social, cultural, or humanitarian character.” Urbanization is fundamental to these and to the all-important issue of the future of Earth’s environment. Over the next forty years, the global urban population is expected to increase by 1.3 million every week. Between 2005 and 2050, the global urban population is estimated to increase by 2.7 to 3.2 billion. Put into a historical context, the global urban population reached 1 billion only after more than 10,000 years of human history; however, today, the global urban population increases by 1 billion about every 17 years. The task of designing new and redesigning existing urban centers to accommodate the growing urban humanity is and will continue to be enormous.

Urban form and infrastructures “lock-in” patterns of behavior and consumption. Once in place, urban form and infrastructure have long life and are not easily changed. Therefore, the kinds of towns and cities that ultimately transpire over the first half of this century will have significant implications for all aspects of life on Earth: the resources required to construct the built environment will transform rural hinterlands from where these natural resources will be extracted; the water, energy and power required to operate and maintain urban structures has the potential to exacerbate global climate change; urbanization will transform societies and economies within and outside of cities.

We know a “good” city when we are in one: they enable individual and collective creativity and innovation; they are safe; they foster community and urban citizenship; they are engines of economic growth and help to eradicate extreme poverty, improve access to education, and help to promote gender equality through access to education and employment opportunities; and they are highly functional with effective urban institutions and governance. Because urbanization is one of the megatrends of the twentieth century that will affect multiple aspects of human and environmental well-being, it is imperative that the UN SDGs provide guidance for what constitutes urban sustainability.

Can the goals of urban sustainability be achieved through sectoral-level SDGs? Unlikely. Many of the opportunities and challenges of urbanization are at the intersection of several sectors that operate at different spatial and temporal scales. Cities are natural hubs for integrating across systems to find unique solutions not possible through one sector alone. There is an enormous window of opportunity to shape urbanization and humanity towards sustainability. Solving urbanization challenges will result in numerous co-benefits and positive windfalls. This requires leadership and guidance that can be achieved through the UN SDGs.

Goals and Outcomes

Christopher Small is Lamont Research Professor, Lamont Doherty Earth Observatory of Columbia University.

Consider a map of the world.  The map is a concise spatial depiction of our world. A two-dimensional projection of a more complex reality.  The words on the map typically represent three things: cities, countries and features of the physical environment like oceans, rivers and mountains.  The physical environment preceded the cities and countries.  Countries were preceded by kingdoms.  For at least as long as there have been countries and kingdoms, there have been cities.  Over the course of recorded history, most countries are temporary.  Cities typically persist and grow, while countries come and go. Over the course of recorded history, cities have proven to be more sustainable entities than countries.  Cities are the emergent consequence of human interaction beyond the scale of families and tribes.  Cities are the engines of human progress, where individuals congregate and cooperate to achieve outcomes.

The success of the city as the incubator of progress is, in part, the emergent result of a feedback between circumstance and intention.  Circumstance enables intention and intention creates circumstance.  Goals are manifestations of intention.  Outcomes are determined by circumstance.  Goals and outcomes have been central to the success of every city.  As global networks of cities evolve more rapidly, goals and outcomes will need to extend beyond individual cities to the network as a whole.  Goals must be explicit and outcomes must be measurable.  This will require accurate, systematic mapping and monitoring of the network – from interconnected megacities to small isolated settlements.  The United Nations’ Sustainable Development Goals could provide a basis for outcomes that increase the sustainability needed for long-term success.   In order to achieve the desired outcomes, the goals must acknowledge the roles and needs of cities explicitly.  In order to verify success, the desired outcomes must be measurable, and they will need to be measured.

Global Traffic Risks for Women and Children: The City is the Key

Marilyn S. Sommers is Lillian S. Brunner Professor of Medical-Surgical Nursing, University of Pennsylvania.

As the global health book Women’s Health and the World’s Cities, and Penn’s recent conference, Urban Women’s Health in the United Nation’s Post-2015 Agenda, point out, there are many intersections between women’s health outcomes and urbanization. Progress on these need to be monitored to focus the world’s attention. Here I discuss one—the reduction of road traffic fatalities and injuries—an important focus of the UN’s Sustainable Development Goals. The need to emphasize traffic injury prevention for the transportation, urban planning, law enforcement, and health sectors is critical. The risk of traffic injury for women and youth is growing globally and is a serious cause of death and disability.

Urbanization and congested traffic patterns compound the health risks. In low- and middle-income countries, passengers on bicycles, motorcycles, and three-wheeled vehicles (often women and children) do not wear helmets or safety restraints even though drivers wear safety protection. Urban crowding creates treacherous roadways for multiple vehicles.  Pedestrians (again, often women and children) are at risk on streets without sidewalks, crosswalks, or traffic signals. Speeding is an international problem both on city streets and rural roads. The UN notes that around the world, speed limits are routinely flaunted, placing both passengers and pedestrians at significant risk for injury.

To complicate the problem, traffic safety laws in many countries do not account for the huge increase in vehicular traffic over the past two decades. The Sustainable Development Goals set the standard for 2030, to reduce road traffic injuries and fatalities globally by 50 percent. Safe and sustainable transportation in cities is critical for long term health, with coordination between transportation, urban planning, law enforcement, and health sectors an essential part of injury prevention. Only with a focus on urban traffic patterns can the Sustainable Development Goal for traffic injury be met.


Richard Weller is Professor and Chair, Landscape Architecture, School of Design, University of Pennsylvania.

Herbert Girardet is right when he says there “will be no sustainable world without sustainable cities.” He is right because cities can no longer be conceived as cultural objects distinct from nature’s benign backdrop. Rather, cities now form a global network that is co-extensive with and woven into the world’s ecosystem at every point. Cities are best now understood as intensifications, confluences and bottlenecks in larger global flows. 

The practical manifestation of this conceptual evolution of the city from machine to metabolism is the redesign of buildings, open spaces and infrastructure. But as that evolution takes place it is important to also note that this is more than just a green optimization of the city of bricks and mortar, it must also include the broader landscapes upon which our cities ultimately depend.

Emerging goals and targets such as the Sustainable Development Goals are an important expression of the gradual translation of theory into practice.  They serve as points of orientation and agreement and encourage healthy competition as cities everywhere to improve their ecological and economic relationships. To that end, emerging Sustainable Development Goals should also look to the UN’s Convention on Biological Diversity Aichi Targets and ask the question: “How can cities now positively contribute to global biodiversity?” For it will be in answers to that question that the emerging conception of the city that Girardet gives voice to will really take shape.


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