A review of the main challenges to urban sustainability

Abstract

Considering the existential threat that global warming poses to humanity, the current focus on climate change is undoubtedly justified. However, this should not overshadow the fact that sustainable development does not only end with environmental concerns but also covers social and economic domains that are mediated through physical spaces and built form. There are two-way interactions between these domains with each having a reciprocal impact on the other. Based on the institutional and policy context, these interactions can move us towards either a more virtuous circle of development with more equitable growth, empowered communities, liveable spaces and reduced (or at least controlled) levels of pollution, or the reverse. Consequently, in order to set the scene for the launch of the International Journal of Urban Sustainable Development, I attempt to provide an overview of the main challenges emanating from each domain for achieving urban sustainability and the contribution that the new journal can make to this debate.

Keywords:

• sustainable urban development
• urbanisation
• urban growth
• globalisation
• governance
• environmental pollution
• social development
• economic viability
• physical development

1. An urbanising world

The twenty-first century has been called the urban century with more than half the world's population living in towns and cities. In the South, though, the demographic shift to a majority urbanised state is expected to be reached before 2020 (WUP 2005) and in Africa not before 2030. The trend, however, is clear with ‘the urban’ continuously outgrowing ‘the rural’. In the next two decades, cities in the developing world will absorb 95% of urban growth (UN-Habitat 2006). Moreover, the rapid rates of urbanisation have led to the growth of megacities of over 10 million in developing countries. In 1975, there were three megacities in the world: Tokyo, New York and Mexico City. In 2005, there were 20 such cities, 16 of which were located in the developing world (WUP 2005).

In many countries, although there is a sentiment for limiting urbanisation through, for example, rural development, research shows that rural–urban migration is unlikely to reduce through such activities and ironically may even increase because of enabling higher mobility of rural households. Fay and Opal (2000) argued that the rate of urbanisation is not necessarily related to economic growth in cities but that it has an inverse relationship to the level of urbanisation in a country, particularly in the African context. Based on their analysis of 187 cities in 100 countries, they have aptly described this process as urbanisation without growth. Writing from a perspective critical of orthodox neoliberal development, Atkinson (2004) came to a similar conclusion noting that, in southern countries as a whole, only around 10% of the people entering the workforce find employment in the formal sector. The vast majority of the urban populations in these countries, therefore, are making a living through various forms of informal employment – some of it secure and well paid, most of it not.

2. Cities as engines of growth and development

Cities and towns are now recognised as pivotal for development. Cities contribute up to 55% of gross national product in low-income countries, 73% in middle-income countries and 85% in high-income countries (UN-Habitat 2006). In some cases, the contribution of a single megacity, for example, Sao Paulo or Bangkok, can be as high as 40% of the gross national product while comprising only 10% of the population of their respective countries. The concentration of people and activities at high densities in cities enables resources to be used more efficiently than in rural areas. They also generate a disproportionate amount of revenue for governments. The role of cities in the growth of national economies is perhaps best illustrated in China where urbanisation is an explicit government policy for accelerated economic growth and raising tens of millions of poor rural peasants out of poverty. At the same time, local city governments have utilised the associated demand for housing and property development to massively boost their revenues through the sale of land use rights to private developers (Cao and Keivani 2007).

The economic role of cities has gained even more significance in the current era of economic globalisation (Keivani et al. 2001, Sassen 2001): they serve as centres for finance and producer services; they are areas of innovation and they are the powerhouses of manufacturing and consumer markets.

The new economic era may also be defined as a global network of flows of people, ideas, finance and goods (Castells 1996, Harris 2001). In this new economy, cities are not only locations of production and consumption but the junctions of flows that facilitate global economic activities. In other words, cities are where the work of globalisation gets done. This implies providing the necessary physical infrastructure, human resources and institutional framework that in turn have major consequences on urban governance, resource allocation and utilisation.

In addition to their economic function, cities are also places of cultural and social interaction. The critical density of people, that allows for agglomeration economies, also provides greater opportunities for reflexivity, information and knowledge sharing, cultural exchanges and more effective provision of services, particularly health and education. All of these are essential elements for social development, advancement of civil society, well-being, cultural consolidation, change and cosmopolitanism. Cities are also centres of political power and administration. The closer proximity to the seat of power, their higher concentration and better articulation of their demands through civil organisations have meant that in the main urban citizens have greater opportunities for influencing policy-making and setting developmental agendas at both local and national levels.

3. Globalisation

Economic globalisation has allowed for a new international division of labour and territorial specialisation based on existing and acquired competitive advantages. We have witnessed rapid de-industrialisation in many metropolitan cities in the North and a parallel growth of higher value corporate service, knowledge-based and creative industries. In London, for example, between 1971 and 2003 the contribution of the manufacturing sector to the city's economy reduced from 25% of total employment to about 6%, whereas the shares of business and financial services increased from 16% to 33% (Harris 2006).

In this process, many cities of the South are emerging as international business and industrial nodes, attracting much of the relocated lower value-added industries because of the comparative advantage of their low labour costs and the development of infrastructure and transport capacities for supporting decentralised production and access to the world markets (Sassen 2002, Keivani and Mattingly 2007). At the same time, many such cities are also rapidly developing their institutional, infrastructure and human resource capacities to maintain and improve their competitive position, not only in respect of industrial foreign direct investment but also to rise in the hierarchy of international nodes of higher value-added functions in corporate services, knowledge-based and creative industries in their own right. The prime examples are Singapore and Hong Kong who shifted their economic base in successive phases from the sweatshops of the 1960s to international centres of the high tech and information technology and regional headquarter and export service centres of Asia as a whole (Macleod and McGee 1996, Ho and So 1997, Sim et al. 2003). Other emerging global hubs from Bangalore, to Bangkok and Shanghai to Sao Paulo, are also following suit with different degrees of success as regional hubs, positioning themselves to achieve the same type of global functions.

Globalisation is highly pervasive affecting not only the large agglomerations but also many smaller cities, towns and even villages and peri-urban areas. Prime examples can be seen in the economic restructuring in villages and small towns surrounding major metropolises. Leaf (2002), for example, highlighted the transformation of agricultural villages around Guangzhou in China and Hanoi in Vietnam to either upper income residential estates for the new middle classes or small-scale manufacturing centres feeding production in the core urban areas. Other examples can be seen in the impact of outsourcing activities particularly in borderland areas of major economies/cities. Some of the most prominent cases can perhaps be seen along the Pearl River Delta in a process that was described by Sit and Yang (1997) as Exo-urbanisation with rapid integration of small towns in the global economy encompassing rural industrialisation, rapid migration and dramatic physical and spatial transformations directly as a result of major outsourcing investment primarily from Hong Kong. Similarly, we can also note agricultural investment in rural farms in Zambia and Mozambique by investors from Zimbabwe and South Africa or the development of major rural eco-tourist destinations attracting visitors from across the globe. Perhaps even more dramatically, one can note recent large-scale agricultural investments by the United Arab Emirates in Sudan to ensure a measure of food security in uncertain market conditions in the Persian Gulf (Sudan Tribune 2008).

Other important considerations in relation to the impact of globalisation on cities include large-scale labour migration and remittances. This can be domestic or international. The former is exemplified in the case of China and the latter can be seen, for example, in labour migration from Moldova to Russia and from the Philippines or South Asia to the Middle East. What is important here is not only the effect of large-scale in-migration on destination towns and cities but also the effects of out-migration on origin cities that in many instances are largely reliant on remittances as a major source of income and livelihood for the remaining population. The latest World Bank data for 2008 indicate that international remittances to developing countries as a whole accounted for $338 billion amounting to about 1.9% of GDP in these countries (World Bank 2009a, 2009b).

4. But is it sustainable?

The fact that cities create wealth, enable global economic functions and offer greater life opportunities for their inhabitants does not negate the challenges they pose for sustainable development.

(1) On the social front, cities are prone to huge intra-urban social inequalities. In the North, this is often manifested in terms of relative income poverty, crime, the social exclusion of particular sectors of society (migrants, youth, the unemployed, and the disabled) and the challenge of engendering more inclusive and responsive governance. In the 2005 Bristol Accord, the European Union placed the development of sustainable communities at the centre of its urban policy emphasising among other things inclusivity, equity, fairness, good governance, safety and accessibility (ODPM 2006, Colantonio 2007). All of these concerns also apply in many cities of the South but they are also faced with the far more severe context of relative and absolute levels of poverty and exclusion. There are almost a billion people living in slums in cities throughout the developing world – one out of every three city dwellers (UN-Habitat 2006). The rate of growth of the world's urban population estimated at 2.24% is roughly equal to the rate of growth of slums estimated at 2.22%. The same figures for Sub-Saharan Africa are 4.58 and 4.53%. In sum, we are witnessing what Nicholas You (2007) described as the urbanisation of poverty where the urban population is just as likely to suffer from malnutrition, disease and hunger as their rural counterparts. To this we must add highest prevalence of HIV among women, infant mortality, sexual and general violence and crime.

A major concern in many cities that also accentuates economic inefficiency and the environmental side effects of rapid urbanisation is the often opaque, exclusive and unaccountable style of urban governance and management leading to skewed and elite decision-making. Relevant factors that may be considered in such analysis include historic and institutional factors and land market processes that have created unequal urban development patterns and hinder the creation of more efficient, equitable and accessible systems.

Nevertheless, such social and societal problems are being addressed in many cities at different levels and by different institutions. Promising initiatives can be identified in the recent shifts in slum upgrading towards more integrated approaches. For example, in Brazil, comprehensive slum upgrading programmes link employment and income generation with physical redevelopment and the integration of slum neighbourhoods into the city fabric.

(2) On the economic front many cities in both the North and South are faced with severe challenges for sustainable economic growth. Cities in the North are struggling with the after effects of large-scale economic restructuring in a rapidly globalising era that has seen loss of major industries and previous economic identities. Such cities are striving to reinvent themselves by focussing on one or more alternative sectors such as corporate services, knowledge, creative, cultural and tourist-based industries. Many have been successful in turning around their main economic base (e.g. Birmingham, Barcelona).

Similar issues are also evident in cities of the South. However, the scale is generally of a different magnitude and is often complicated by severe institutional weaknesses and the lack of material and financial resources. Addressing severe levels of income poverty through sustained policies for local economic development and income-generating opportunities for low-income households is of direct relevance to both social and environmental development in cities of the South. The absence of strategic economic vision, the lack of coordination between different levels of government and compartmentalised sector-based policy-making not only lead to duplication and wastage of resources but can also entail conflicting objectives and ineffective policy interventions. Crucially as many commentators have noted, the primary concern of the poor is to earn a living rather than look after the environment (Drakakis-Smith 1995, Werna et al. 2009).

A related concern is that of municipal finance. This is highly important not only to the municipal investment in capital projects for supporting economic activities but also to the provision of essential city services, e.g. green space, garbage collection, recycling, street lighting and to offer social support activities, e.g. youth training and community development. Important issues include direct and indirect methods of raising municipal revenues and ways of involving private and community resources through both formal and informal partnerships. Successful experiences include new innovative schemes for better utilising corporate social responsibility initiatives and participatory budgeting to better target what is actually needed on the ground and to foster community ownership. The primary example of this is perhaps seen in Porto Alegre that pioneered participatory budgeting in 1989 and according to some estimates it has now been adopted in over 1200 municipalities worldwide in both southern and northern cities (Wikipedia 2010).

(3) On the environmental front, we are faced with several different but related issues with different degrees of influence in northern and southern cities. First are the global concerns over the release of greenhouse gases (GHG) and their impact on the world climate. Cities are by far the largest contributors to GHG emissions. They consume 75% of the world's resources and produce 80% of CO₂ emissions (UN-Habitat 2005). It is, therefore, at the city level that greatest efforts must be concentrated to reduce GHG emissions and tackle pressures of climate change. This requires sociotechnical approaches at both macro- and micro-levels encompassing innovative sociotechnical solutions, institutional frameworks and shifting cultural attitudes for reducing energy consumption, encouraging renewable energy production and changing consumption patterns and lifestyles. The need for remediation measures for reducing energy use and GHG emissions is applicable to both northern and southern cities. However, international obligations for GHG reduction, greater local social and political awareness and higher resource and institutional capabilities have placed the former in a stronger position to develop and apply remediation policies. Nevertheless, this is a global problem that requires a global solution. A recent study by Urge-Vorsatz and Novikova (2008) indicated that the greatest economic potential (at net negative costs) for mitigating CO₂ emissions in buildings lies in developing countries. This is because many of the low-cost opportunities for CO₂ abatement have already been captured in the more developed economies because of progressive policies in place or in the pipeline. Greater remediation efforts are required in cities of the South that also have direct social, economic and health benefits for their citizens. Important areas for consideration include optimal scales of governance and the mix of policy instruments that can and should be applied (economic, legal/standard setting, combinations of legal and economic instruments) for specified interventions. Additionally, we also need to consider the capacity of actors to effectively enforce the instruments of environmental policy. Finally, note must be taken of more critical debates emphasising paradigmatic shifts from what is considered to be the current dominant neoliberal development model primarily based on continuous growth and excessive consumption to more controlled growth and community-focussed development alternatives (Atkinson 2004, 2007).

The second issue is the negative impact of climate change on living conditions as witnessed in recent floods, heat waves and hurricanes in Europe, the Caribbean and North America. To this must be added earthquake and tsunami hazards with their massive potential for exacting human and physical costs as witnessed most recently in Indonesia and Haiti with the virtual destruction of entire cities and colossal loss of life. These have necessitated adaptation measures for enabling cities to cope better with destructive forces of an increasingly volatile climate and other natural hazards. Here it must be emphasised that the greatest negative effects of environmental change and natural hazards are felt in the informal settlements of the South that are often ill constructed, badly sited and under-serviced and are particularly prone to severe climatic and natural conditions (Wilbanks et al. 2007).

Other concerns relate to general environmental pollution, resource management (particularly water) and loss of agricultural land arising from urbanisation, urban sprawl and industrial activities. This has some resonance in northern cities but the main concerns lie in developing countries primarily because of institutional inability to implement regulations and manage natural resources. For example, in China more than one third of industrial wastewater and two thirds of municipal wastewater is released into rivers without any treatment (Wen 2005). This means that 60% of the country's main rivers are now regarded as unsuitable for human contact. At the same time, many Chinese cities face severe air pollution with some studies claiming that it claims some 300,000 lives prematurely (Wen 2005). A major consideration here is examining capacities, priorities and ways of implementing and institutionalising Local Agenda 21.

To different degrees, most developing cities are suffering from one or more environmental side effects of rapid urbanisation and industrial growth. In addition to the example of China, they can be seen in the contamination of water tables in Curitiba in Brazil because of rapid and unorganised urban sprawl onto protected areas, the loss of agricultural land around Egyptian cities estimated at a total of 1.4 million acres between 1952 and 2002 and severe air pollution in Tehran that is described as ‘collective suicide’ and estimated to kill some 3600 people a month (El-Hefnawi 2005, Terradaily 2007).

Research also shows that although pollution initially increases, with rising incomes and economic development the actual rate of pollution actually reduces and is eventually reversed as has been noted in the reducing trends in the production of particulate air pollution during the 1990s in Chinese cities, Mexico City and Cubatao in Brazil that was once known as the valley of death because of its severe industrial air pollution (Wheeler 2000).

In addition there are also major successes in terms of institutional interventions. For example, the remarkable turnaround of Cubatao in Brazil is largely due to the success in enforcing strict pollution control measures on industrial discharges. This has led to more than halving particle discharges since the mid-1980s and for the city authorities to be able to hold it up as a model not only of environmental recovery but also of sustainable industrial development (Milliken 2000). In terms of urban planning and city management, there are many encouraging examples in the transport sector including multi-modal-integrated transport policies (e.g. Curitiba, Brazil) (Globalideasbank 2008), various forms of congestion charging or limiting vehicular traffic in to central locations (e.g. Singapore, Mexico City and also Tehran), replacement of petrol/diesel fuel (e.g. for 60,000 auto rickshaws with compressed natural gas in Delhi). Nevertheless, the Curitiba and Tehran examples both highlight the ill-effects of partial approaches to sustainable development and environmental protection. The former whilst introducing exemplary transport policies in some areas is still facing rapidly deteriorating sociospatial evolution and environmental conditions in its periphery and the latter is still choking in traffic fumes despite the controlling traffic in central areas.

(4) Access to utilities and basic infrastructure. In many southern cities, lack of access to basic utilities is not only a major impediment to sustainable economic growth and productivity but also a major cause of urban inequity and ill health (Werna et al. 2009). Despite recent international data that indicate that 95% of urban populations in developing countries have access to drinking water (World Health Organisation/UNICEF 2006), such general figures hide extreme variations across the developing world both at present and in the future. For example, Brazilian, Mexican and Chinese cities generally have a much higher level of access than Indian and African cities. Overall, however, researchers have noted that in low-income cities of developing countries, only 50% of households have water piped to their homes (Arimah 2005). In many cases, therefore, access can mean communal taps rather than actual household connections. In addition half or one-third of those that are connected only get intermittent access. In India, for example, a study of 35 urban centres representing 15% of the urban population of the country found that water was supplied on average only seven hours per day (Nickson and Franceys 2003).

Bearing in mind the continuing high rate of urbanisation in developing countries, the situation will be even more critical in the near future. It is, for example, estimated that urban Africa will require an 80% increase in the numbers connected to main water networks to meet the millennium development goal of halving the unserved population by 2015 (Mukami Kariuki 2002). Clearly, scaling up to the level indicated is a monumental task in many developing countries because of the lack of material, financial and human resources. This becomes even more daunting when considering that a large portion of the population in developing cities live in informal and shanty settlements where local authorities may in fact be barred from providing utilities because of the illegal status of the settlements or because of precarious locations and unplanned layouts that make extension of services very difficult even if governments were willing to extend them (Nickson and Franceys 2003). This is compounded by lax monitoring and the enforcement of legislation itself, leading to a vicious cycle of poverty, sociospatial exclusion, irregular land use patterns and slum formation in environmentally sensitive areas, and subsequent costly slum-upgrading programmes. Poor households often have to pay vendors several times the unit price paid by connected non-poor households to the utility (Gulyani et al. 2005). The situation with access to electricity, sanitation and refuse collection is invariably worse than that of water. These have major implications for social and economic development as well as exacerbating environmental pollution because of usage of open ground or unlined pit latrines for sanitation in some cities, or inadequate disposal of household and industrial refuse (Werna et al. 2009).

Consequently, greater attention needs to be paid to specific policy and technical approaches that provide more immediate solutions that have the potential for scaling up to make a tangible impact on the situation of the low-income groups in developing cities. For example, in their contribution to this volume Christoph Lüthi et al. argue for combining Household-Centred Environmental Sanitation and Community-led Total Sanitation in addressing the challenge of sanitation in a sustainable manner in urban and peri-urban areas. These are seen to combine the benefits of both a community-led and a structured planning approach leading to behavioural change and multi-stakeholder involvement necessary for providing more sustainable solutions.

(5) Urban form and spatial development have major consequences on the sustainable development encompassing not only environmental issues but also social and economic aspects. The concept of compact city development aims to optimise energy use, promote renewable energy sources, provide integrated transport networks with a focus on enhancing public transport and cycle routes, change the culture of energy and resource consumption and increase social inclusion (Jenks and Jones 2010). Ultimately, such action would also enhance economic productivity through better connectivity and resource saving. These issues are as relevant to northern cities as they are in the South.

An important consideration under this heading is the impact of major urban development and infrastructure projects initiated by both the public and the private sectors with direct consequences on all aspects of the sustainability paradigm, in particular urban equity. These developments are often foreign direct investment-driven and globally induced aimed at raising city competitiveness but have unforeseen and/or unaccounted externalities. They often entail conflicting claims to land and city resources between local inhabitants and the actual or perceived requirements of global capital. They can occur both in established or peri-urban and in peripheral city areas. In southern cities, however, they often impact on informal low-income communities with precarious tenure rights and income-generating opportunities or peasant communities (Keivani and Mattingly 2007, Werna et al. 2009). They can lead to major social tensions, particularly as a result of forced displacement with inadequate social and financial compensation, sidelining of local requirements and imposing elite governance practices. This can affect cities in both the North and the South although the rate of developments and the scale of displacement in the latter have tended to be much higher (Swyngedouw et al. 2002, Keivani and Mattingly 2007, Werna et al. 2009).

Nevertheless, they can also enhance the city economy and have the potential for local economic development benefitting the lower income groups and small and medium local enterprises. The key issue is to set in place the appropriate institutional framework and governance mechanisms for policy-making and implementation that would allow for a more balanced and pro-poor approach to urban spatial organisation, land use and affordable housing optimising both global and local developmental benefits.

In addition, rapid and dynamic urban growth in developing cities often leads to new patterns of agglomeration in peri-urban areas with their own unique social and economic challenges, opportunities and developmental priorities. The problem is compounded by the massive growth of gated communities for the middle and higher income groups that often impinge on peripheral land occupied by poor slum dwellers and peri-urban farming communities and create particular problems of social exclusion and lack of fit within the broader urban fabric. A particularly severe example of this can be seen in the Metropolitan Area of Buenos Aires where Thuillier (2005) noted that there are about 350 gated communities, covering 300 km² of land, and hosting approximately 50,000 permanent residents. However, similar development patterns can be observed across a range of cities in the South including China and India in the past decade (Leaf 2002, Cao and Keivani 2007, Keivani and Mattingly 2007).

An important consideration for more equitable spatial development in the new locations as well as the more established parts of cities relates to upgrading existing informal settlements, providing more secure tenure/entitlement and enhancing low-income access to land and infrastructure resources for housing and income generation activities. This can involve innovative sociotechnical approaches that can seek to provide both supportive institutional frameworks (e.g. different tenure arrangements to support asset consolidation and innovative and inclusive governance and partnership vehicles involving a range of actors) and financial and technical support for a range of measures including physical upgrading and redevelopment, innovative and low-cost engineering solutions and green refurbishment/adaptation encompassing both energy-saving measures and affordable renewable energy technology.

(6) Multi-level governance and institutional development. Throughout the previous discussion, urban governance and institutional capacity are highlighted as essential requirements for addressing the main challenges for urban sustainability.

Governance refers to the process of delivering government through the inclusion of non-government actors (Jones and Evans 2006, Werna et al. 2009). From a multi-level governance perspective, important considerations are (i) the competence and coordination between the vertical levels of government and (ii) horizontal levels of governance both in terms of transnational and intra-city linkages and patterns of governance between different city government structures as well as power relations and networked interaction between different public, private and community actors in decision making and policy setting at local and metropolitan levels and the way that they feed into higher levels of decision-making (McGuirk 2000, Rakodi 2004a, 2004b, Corfee-Morlot et al. 2009). The former, subsidiarity, is crucially important for ensuring effective urban management. For example, the resurgence of metropolitan governance institutions in Western Europe in the 1990s can be seen not only as instruments of regional competitiveness but also to enable a more comprehensive response to alleviate the negative side effects of localist urban entrepreneurialism and local regulatory downgrading of the neo-liberalising political environment of the 1980s (Brenner 2003). The latter, on the contrary, is critical for ensuring an inclusive, responsive and accountable governance process that is not only important for social considerations but also can have direct positive effects for improving economic and environmental impacts of urban development.

Any discussion of governance must consider the impact of strategic planning for enabling flexible responses to uncertain urban futures particularly in the context of economic globalisation and climate change. This approach has been adopted in the cities of the North at least since the early 1980s in their efforts to reinvent themselves in the face of severe economic crisis and loss of their more traditional industries. This has led to a proliferation of various medium- and long-term economic and development strategies at both metropolitan and city district levels. Partly based on this experience and recognition of the multi-faceted problems of economic and physical growth in cities, since 1998 the World Bank and later the Cities Alliance have advocated the adoption of city development strategies (CDSs) in developing countries as a way of providing a holistic strategic approach for addressing the main perceived challenges. The stated objectives of a CDS are

•	enhancing city economies,
•	reducing poverty,
•	protecting the environment,
•	enhancing local revenue-raising capacity and city financial management.

By 2009 more than 200 CDSs had been formulated and applied in different cities across the world with different degrees of success. Some commentators have argued that CDSs and strategic planning aimed at strengthening economic competitiveness are local applications of the ‘Washington consensus’ and the neoliberal growth paradigm that will reinforce historical patterns of social and spatial exclusion. On the contrary, a more positive and pragmatic view argues that unless city managers have a strategic understanding of the weaknesses, strength and potentials of their cities and where they fit within the broader national and regional economies they cannot really take effective action to address their shortcomings. From this perspective CDSs and strategic urban planning, therefore, do have a role to play and are essential for providing such a strategic perspective that can then guide follow-up actions.

5. Concluding remarks

In this discussion, I have tried to set out the main challenges that we face in terms of urban sustainability. What it highlights is the multi-faceted nature of the sustainability debate in towns and cities where large concentrations of people and activities have created a myriad of complex social and economic challenges with often severe environmental consequences including the greatest contribution to atmospheric, water and ground pollution. This is exacerbated in the South by rapid and continuing urbanisation and the relocation of manufacturing and heavy industries to emerging industrial hubs that have comparatively limited resources for monitoring pollution and for providing jobs, incomes and livelihoods.

Yet cities also provide the greatest promise and potential for addressing many of these challenges. The same concentrations of people that underlie the challenges also provide the agglomeration economies for more efficient use of resources and provision of services and the space for greater innovation and productivity. In the current time of rapid global integration, both the threats and opportunities for achieving more sustainable cities have increased. On the one hand, for example, we are prone to risks associated with increased global economic volatilities, conflicts between local needs and global capital requirements in terms of access to city resources and public investment, increased risk of social and cultural alienation and rapid rise in energy use and pollution as a result of continuing global economic expansion. On the other hand, economic globalisation can also enhance city economic performance with additional opportunities for employment and local economic development. The degree to which local population and poorer groups can benefit from these changes largely depends on governance and decision-making that can manage the process to maximise local benefits and provide a better balance between global and local priorities. In addition, despite the seeming failure of the 2009 Copenhagen Summit in setting new legally binding targets on GHG reductions, global and regional environmental governance structures are being developed. As Adrian Atkinson has noted in his contribution to this issue of IJUSD, the success of such governance structures is largely dependent on the courage of the political leaders and their ability to face up to what is required to control and reverse global warming. Such governance structures provide the basis for high-level policy debate on the subject that can have a real impact at the local level, e.g. Rio and Kyoto agreements on CO₂ reduction targets. The degree to which the targets are likely to be met universally is subject to debate. Nevertheless, they have slowed CO₂ emissions in the countries that ratified the agreement, providing the institutional framework for developing and implementing effective and binding anti-pollution measures at the local level.

Considering the complexity and range of issues at hand, it is not surprising that in her contribution to this issue, Katie Williams notes that while the discourse itself is relatively mature there is still a lack of consensus on precise conceptualisations. Indeed, according to some accounts there are over 200 different definitions of sustainable development (Parkin 2000). Consequently, Williams identifies two main challenges that should underpin future research: (i) understanding ‘what the sustainable city is’ and (ii) ‘how to bring about sustainable urban development’. These challenges necessitate the understanding of different perspectives on urban sustainability that may help in breaking out of the ‘silo mentality’ of the disciplines that are involved in urban development. This is critical for moving towards greater consensus on basic definitions and developing more effective policy and sociotechnical solutions to specific problems. Wider dissemination of the debates across the disciplines will also help achieve cultural shifts among academic, practitioner and public stakeholder groups that can be major drivers for more radical paradigmatic shifts.