By 2030, it is estimated that 65 percent of the global population will live in cities.1 In the longer term, the world’s population is projected to be 10 billion by 2050 with most of the additional three billion living in cities. To accommodate these extra three billion people, we will need to build the equivalent of one new city that can support one million people every five days between now and 2050.2 In practice, most of these people will be accommodated through the expansion of cities, with the consequence that, by 2030, the world is projected to have 41 megacities with more than 10 million inhabitants, including Tokyo with 37 million and Delhi with 36 million.

Population growth is just one aspect of urbanization. It is accompanied by the urbanization of the landscape, which can expand even faster than urban population growth.3 According to the World Bank, the urban area in the Pearl River Delta grew from 4500 sq. km. in 2000 to nearly 7000 sq. km. in 2010.4 As cities are typically located in fertile land, the consequences of this expansion for agriculture and the food security of urban populations have become matters of increasing concern.

Urbanization can take different forms, ranging from the growth of existing cities (Mexico City), to the merging of several urban centers into urban regions (Pearl Delta Region, China) and corridors, and to the emerging ‘smart’ cities developed on sustainable principles (Songdo, South Korea).

Urban agricultural plots lie below high rises in Songdo, South Korea. The city was designed as a new ‘smart’ city, built with sustainable principles.

Major drivers of urbanization include push factors from rural areas when traditional livelihood becomes impossible, and pull factors from cities with better employment and education opportunities. The migration between rural areas and cities is becoming increasingly mobile and bidirectional, for example, increasing circular migration in sub-Saharan Africa or the large number of floating peasant workers in China,7 largely responding to economic opportunities in urban areas. A third driver of urbanization is the targeted governmental policy to promote urbanization for economic growth, as urban expansions feed into economic growth,6 and urbanization is closely linked to an expanding middle class, particularly in rapidly industrializing countries such as China. The the increasing consumption power of these new urban middle classes is seen by governments as a new driver of domestic demand and economic growth17.


There are numerous challenges associated with rapid urbanization. Providing for rapidly growing urban populations, managing air pollution, reducing carbon emissions, preparing for climate change risks, and improving social integration and governance procedures are several examples.

The provision of sufficient and affordable infrastructure, such as housing, water supply, sanitation, and transportation options to meet the demands of a growing urban population requires large investments in cities. In addition to the financial requirements, planning for smart infrastructure is a key consideration that will require investment in knowledge and skill development at the national and local levels. In particular, national energy systems servicing large urban conurbations will experience transformational change in the very near future. Indeed, the roll-out and integration of renewable energy into old and new cities has become a priority for many large utility providers.

Air quality is an example of the possible negative externalities of rapid urban expansion. This is being experienced in a very tangible way in large developing nations. During early December 2015, the first two red-notices for ‘heavy air pollution’ were issued by the China Meteorological Administration, highlighting the growing human health dimension of maintaining a sustainable city.7,8  The social and economic consequences of these notices were immediate and severe, as they required the closure of factories, businesses, and schools. Another example is the Asian brown cloud that sweeps over Asian countries, including India and Malaysia, highlighting the interconnectedness of urban and natural systems. Primarily generated by wood and forest fires, transport, and industrialization processes, the brown cloud is having a major impact on human health.9

At the larger scale, climate change is one of the greatest challenges. Cities are major contributors to global carbon emissions, accounting for 75 percent of world final energy use and 76 percent of carbon dioxide emissions (both numbers are median figures from the estimated range).10,11 In high-income countries where urban rural income disparity is less significant, cities can scale benefits to provide infrastructure more efficiently, and thus can be less carbon-intensive than in rural areas. In developing countries, on the other hand, urban–rural income disparity remains significant, with urban dwellers on average consuming more than their rural counterparts, and the urban way of life is typically more carbon-intensive. Finding ways to achieve a low-carbon urban development is an urgent task, as the majority of urban growth will take place in the developing world.

Climate risks and vulnerabilities present enormous challenges for the planning of our cities. Many major cities are located along coastal areas and will suffer from the impacts of climate change (e.g., flooding, coastal inundation, extreme weather). Studies show significant costs from these impacts, with limited adaptation options, and developing cities being particularly vulnerable.12 Planners usually regard the physical environment as relatively stable and rarely consider the possibility of significant changes in the urban landscape due, for example, to large-scale coastal erosion. Indeed, despite the fact that a more dynamic environment will bring with it a raft of legal, social, economic, and environmental consequences, many new developments take place in areas at high risk from flooding and coastal inundation. This requires cities to adapt a planning system that can respond to changes occurring at a scale never previously encountered and to make urban design more climate-sensitive.13 Some global cities such as London, New York, and Melbourne are planning ahead for climate adaptation. However, much of the world’s urban population will continue to live in small to medium urban centers, with half of the world’s urban residents living in relatively small cities of less than 500,000 inhabitants. With only around one in eight currently living in the 28 megacities with more than 10 million inhabitants, planning for cities at different scales is an important consideration.14

Migrant laborers, known as China’s ‘floating population,’ face constant discrimination, economic hardship, and a lack of access to basic public services in the cities that they work in. Here plain-clothes construction laborers from the countryside are seen working in of Guangzhou.

Urbanization also presents critical social challenges. China alone has a ‘floating population’ of over 260 million working in coastal cities. Though vast in numbers, these workers are not fully integrated into the urban fabric.15,16 Wider considerations of climate justice and social equity are also emerging as fundamental societal concerns in planning for cities, climate change, and planetary boundaries.17,18 Exacerbating these impacts will be the potential for increasing social and economic divides in both developed and developing nations resulting in increasing issues of urban access and equity.

Some broader societal trends also present new challenges to cities, for example, planning for an aging society such as in Japan and the revitalizing (or not) of shrinking cities such as former industrial cities like Detroit. These are complex issues that will bring winners and losers within and among cities, whatever the planning response. This diversity of outcomes is nothing new in itself, but the risk that certain groups will be severely disadvantaged increases with the pace of change. For this reason, any strategic planning for urban settlements must consider possible impacts for vulnerable groups such as the elderly, and wider consequences for the region. Indeed, the complexity of these issues highlights the necessity for all levels of government to be involved in developing solutions.


To effectively address the diverse urban challenges ranging from the more traditional issues such as housing, transport, water, and energy to the emerging issues of climate change and planetary boundaries, a consorted approach integrating local, national, and international efforts, and mobilizing all sectors and actors. In this regard, a systems understanding and approach- that is, understanding cities as systems rather than a collection of individual sectors that are nested within larger systems- will be critical to finding solutions for the future.

Solutions are most likely to vary across cities and will be context dependent. Differences may be due to the functional differences of cities or the scale of cities across the urban hierarchy, from global cites such as New York and Shanghai to small coastal urban centers, as well as across the development stages and per-capita income spectrum. Nonetheless, there are some high-level principles in terms of adopting a systems approach (see box). These principles are essential to effectively address urban challenges and build sustainable, resilient, and healthy cities.

10 Principles to make our Cities Liveable19

  • Empower cities: More financial power should be delegated to cities in proportion to their responsibilities. In addition, it is important to recognize their rightful place in policy processes and implementing the Sustainable Development Goals (SDGs). Current implementation strategies emphasize country, regional, and international approaches, without much focus on cities. Challenge cities to adopt the goals—and compete and cooperate to achieve them.
  • National level support: It is important to realize urban issues are not the responsibility of local government alone. The aggregated social and economic power and environmental impacts of cities are often comparable to that of entire nations, but their potential cannot be properly tapped without support. Having a place in the national government institutional structure is essential.
  • Integrate new migrants and other vulnerable populations into the urban fabric: In China alone, there are 250 million people termed the “floating population” who come to cities to work but often without adequate social security or health care support. These people are often systematically discriminated against by cities’ bureaucracies. Adopt a people-centred approach to urbanization, nurturing a sense of belonging and enhanced participatory governance.
  • Beyond city limits: Ensure policies and management decisions at the city level take into account the regional and global context and interactions.
  • Coordinated long-term vision: As cities grow and new cities emerge, we need a coordinated long-term vision of urban development. Unrealistically ambitious outlooks and over competition result in redundant infrastructure and inefficient resource use.
  • Prepare for future risks: Cities need to be prepared not only for the risks arising from global phenomena such as climate change, but also those arising from local processes. For example, numerous cities sit on deltas, and many of the world’s deltas are sinking as a result of extraction and the concentration of high-rise buildings.
  • Implementation and accountability: Many cities suffer from air and water pollution, where local officials prioritize economic development over environmental quality; or worse, corruption is rife and officials are bribed to ignore regulations. Enhancing implementation of environmental regulation and reducing corruption will have a dramatic effect on the liveability of cities.
  • More science in planning and decision-making: We do not have a full grasp of how cities as complex systems behave and respond to intervention. For example, decisions about transport can affect housing, industry, energy consumption, and health in unexpected ways. Unintended adverse consequences can be minimized through closer collaboration on science and urban policies. Moreover, the main urban research institutes are in wealthy countries. The most rapid urbanization will happen in Africa and Asia. We need more urban research institutes in these areas linked to local and national policies.
  • Nurture cultural innovation: Cities are centers of rapid cultural innovation. Evidence shows that cultural shifts in cities, for example, “Cycling is cool” or “Wasting food is a shame,” have the potential to deliver significant sustainability outcomes within and beyond cities.
  • Facilitate city-to-city learning: Cities learn from each other more than from anything else. However, engagement in such peer learning can be constrained by local capacity, and this is where upper-level government and international organizations can help. In doing so, we must recognize that solutions are not one-size-fits-all. It is also important to recognize that learning and sharing doesn’t have to be unidirectional.

There are some encouraging signs and progresses towards finding solutions. The magnitude of urban challenges and the new opportunities of addressing them are increasingly recognized internationally. Recent inclusion of sustainable, resilient, and healthy human settlement as one of the Sustainable Development Goals (SDGs) is one of such example. This year the UN Habitat III conference, a major UN conference that is held once every 20 years, will be held in Ecuador, and a series of global and regional initiatives are being undertaken in the run up towards it. Cities are gaining increasing legitimacy and voice in international policy processes such as COP21, with active participation of local government associations. New international city networks are sharing these experiences at the subnational level, and their presence at the COP 21 meeting was substantial. These new networks may be a significant component of the possible global solutions to the challenges of urbanization. Future Earth, a 10-year global research initiative on sustainable development, identified urbanization and building sustainable cities as one of eight grand societal challenges and is expected to launch the Cities Knowledge Action Network later this year, which will provide a global research and engagement platform on urban issues.20

Peter Edwards, Director of the Singapore-ETH Centre and Future Cities Laboratory speaks at the World Economic Forum – Annual Meeting of the New Champions in Dalian, China in 2015.

At the national level, China announced a National New-type Urbanization Plan in 2014 which, instead of being focused primarily upon the economy and infrastructure, is more people centered. And in Australia, a Minister for Cities has been appointed, emphasizing the critical role that federal government has to play in urban issues, especially in the areas of innovation and productivity. The national government’s role is critical in finding solutions, as urban policy can be strongly influenced by national priorities and strategies. The National New-type Urbanization Plan in China sets a clear target that the share of green buildings in new constructions in cities and towns needs to be 50 percent by 2020, which has the potential to significantly improve the energy and greenhouse gas emission profile of cities.

Within cities, the role of nongovernmental actors in achieving sustainability is increasingly recognized. Universities have an essential role to play in promoting urban sustainability by producing new knowledge and ideas and actively engaging with local government and communities.21 The collaboration between Singapore and Swiss Federal Institute of Technology in Zurich (ETH) is such an example (see box). The benefit of such collaboration is two-directional, with cities providing living labs for researchers to develop theories and perform rapid option testing, as well as benefiting from emerging innovations and tested options of innovative urban research.

Future Cities Laboratory: Innovative Research for Sustainable Cities

A report recently published documents how “the world’s leading universities have embarked on a building boom for urban research.” In the last ten years, more than a dozen labs, departments, and schools have been launched with the common goal of researching quantitative and computational approaches to understanding cities as systems.22 One of these new institutions is the Singapore–ETH Centre, founded in 2010, which supports two major research programs: Future Cities Laboratory (FCL) and Future Resilient Systems (FRS).

Both programs are multidisciplinary and aimed at developing practical solutions to improve the resilience and sustainability of cities. However, any such solutions must be based upon a sound understanding of how cities work, and this remains very limited. As Geoffrey West, former director of the Santa Fe Institute, remarked, we “desperately need a serious scientific theory of cities—relying on underlying generic principles that can be made into a predictive framework.” FCL focuses it efforts upon the ‘metabolism’ of cities, studying them as complex systems characterized by stocks and flows of resources, including energy, water, capital, and information. FRS, on the other hand, relies heavily upon complexity theory, treating urban infrastructure systems as complex sociotechnical systems composed not only of engineered structures, but also of the people who make up the subsystems of users and operators.

Three examples illustrate the kinds of problem-oriented research undertaken at the Singapore–ETH Centre and the challenges it faces in putting new knowledge into practice. The first concerns a project to improve the efficiency of air cooling, which in cities such as Singapore can account for as much as one-third of all electricity consumed. In preliminary experiments, a research team of architects and engineers found it could reduce the energy needed for cooling by as much as 50 percent by using a combination of radiant-heat exchangers, decentralized ventilation, and wireless sensors and controls. And there was another important benefit: the new system needed much less space for ducting and machinery, so that buildings could potentially be smaller and use fewer materials in their construction. But despite these evident benefits, it proved very difficult to find a developer who was prepared to install the first system in a new building. Fortunately, a local private school was prepared to take this risk, and the new system has now been successfully installed in the school’s new administrative block, where it is attracting great interest. The lesson learned from this experience is that new ideas need to be demonstrated. We suggest that cities could contribute to achieving sustainability by providing the opportunities to test new ideas.

The second example concerns a project to develop a new approach to urban river rehabilitation. The river in question is the heavily polluted Ciliwung River in Jakarta, which floods regularly, causing untold misery to residents in low-lying parts of the city. The research team of hydrologists, engineers, and landscape architects used a combination of hydrologic, hydrodynamic, and 3-D landscape modelling to assess the consequences of potential interventions in the urban landscape. Working closely with stakeholders, they developed design scenarios for the Ciliwung as a public green corridor, which would restore the riparian ecosystems and greatly improve the quality of life for local communities. A major public event was organized to encourage public authorities and funding agencies to implement this project, though the response so far has been modest. The lesson learned is that implementing radical solutions requires patience and persistence.

The third example concerns the development of tools for simulating and visualizing urban processes. At the heart of FCL is a sophisticated digital laboratory, Value Lab Asia, with state-of-the-art facilities for modelling 3-D and multidimensional data. As well as being an essential research tool, this laboratory provides an important means for working with practitioners. Architects and planners, for example, can visualize the changing plumes of heat swirling around buildings as wind speed and direction changes and explore how new designs might affect a city’s heat balance. Transport planners can gain a bird’s eye view of the city’s traffic streaming through the streets and test how traffic flow might be affected by adding a new bus route or providing motorists with more information about congestion. Not surprisingly, this facility attracts great interest from industry and government agencies. The lesson learned is that good visualization provides a powerful means for translating research ideas into practical solutions.

In conclusion, the ‘new urban science’ is emerging rapidly as a coherent body of theory and knowledge about how urban systems function and change. Researchers in this field are challenged to leave the ivory tower and collaborate with government agencies and industrial partners in producing knowledge and ideas for a more sustainable urban future. And in doing so, they are changing the ways that universities do their work.

On the social front, the increasing demand of growing urban populations for civic engagement and participation in decision-making processes is making itself felt in rapidly urbanizing cities. A good example is the increasing ‘activism’ in cities such as Shanghai over the loss of heritage buildings and the clear-felling of trees for new development. Enhanced awareness and further empowerment of civil society is needed to push for and engage with inclusive governance practices.

The heavily polluted Ciliwung River in Jarkarta, Indonesia. A research team from the Singapore-ETH Centre have developed design scenarios to revitalize the river as a green corridor.

Various forms of social, technological, and design innovations and experimentation are burgeoning in cities, and solutions proven elsewhere are being adapted and taking root in cities. As part of the Energy Efficiency Improvement program, the Australian Capital Territory recently conducted energy saving house calls, which involved a technician visiting households door to door, changing all the light bulbs and downlights to energy-saving light bulbs, installing door seals, and setting up standby power controllers that turn off televisions after a certain amount of time. This news was shared via social media by ordinary citizens and met with pleasant surprise. The EEI scheme mandates the electricity company to bear the cost. And it is encouraging to see that many such schemes are emerging in rapidly growing cities. The Bus Rapid Transit system developed in Curitiba has now taken root in many Asian cities such as Jakarta, Beijing, and Guangzhou. The bicycle renting system in Hangzhou City is not an innovation in itself, but over 400,000 daily users makes it significant. Studies show such urban sustainability experimentations can play a significant role in sustainability.23

There is still a long way to go in terms of truly embedding sustainable principles in urban policy and practice. In particular, a closer collaboration between the research community and urban policy makers and practitioners is called for to achieve a better understanding of urban systems as well as how to translate such understanding into informed urban policy making and practice.


This contribution is based on deliberations in the session ‘Urbanisation’ at the IARU Sustainability Science Congress 2014.


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Xuemei Bai

Xuemei Bai is a Professor of Urban Environment and Human Ecology at Fenner School of Environment & Society, Australian National University. Her research focuses on urbanization, understanding cities...


Barbara Norman

Barbara Norman is the Foundation Chair of Urban and Regional Planning and Director of Canberra Urban and Regional Futures, University of Canberra. She is an Adjunct Professor with The Australian National...

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