As people move from rural to urban areas, cities all around the world are growing at an incredible rate. Now more than ever it is important for planners to consider the problems and potential in urban development.

The latest United Nations Human Settlements Programme (UN-HABITAT)'s State of the World's Cities Report (2010/11) offers both hope and warnings for cities. While the decade between 2000 and 2010 saw over 200 million people in the developing world lifted out of slum conditions, the patterns of urban development and growth across regions have been uneven. The twin forces of urbanisation and globalisation have heightened the already starkly contrasting socio-economic realities in developed and less-developed economies. Many cities have prospered and continue to enjoy accelerated growth and newfound wealth, visibly displayed in expensive skyscrapers and impressive urban infrastructure. Yet within the same cities, we may witness poverty and deprivation, deficient services and urban decay for those segments of the population who are left behind.

Cities are constantly changing, driven by large-scale population movements, economic and social restructuring, and highly mobile investment capital traversing the globe. The forces of change are complex and could bring forth divergent development trajectories in the future. There are often two sides to the coin: inherently positive forces that drive cities toward greater economic prosperity, could also create social segmentation and lead to more environmental degradation. Increasingly, urban areas have to prioritise alternative energy use to be effective.

For the more prosperous cities, the urban challenges lie in the burgeoning pressures on resources such as land, water and energy, coupled with growing consumption demands and waste generation. Poorer cities may continue to grapple with basic development issues of environmental degradation, inadequate housing and sanitation, aging infrastructure, lack of access to basic amenities, marginalisation of the disadvantaged and other forms of exclusion.

Planners and policy makers need new and enlarged tool kits to deal with the multi-dimensionality and complexity of the issues. Advanced urban solutions have to be sought, and three areas appear to be appropriate starting points:

First, harnessing technological development. The traditional analytical and creative fields of urban planning and design have to be complemented with technological inputs from science, engineering and information technology. Singapore has already shown itself to be adept at harnessing technological advancements to support city development, as seen in urban innovations such as Electronic Road Pricing and NEWater. Continued R&D efforts could bring forth new breakthroughs to address the many challenges in the areas of transport planning, waste management, energy systems and advanced building construction methods. As we can see, tackling the problem of cars can be thorny if you want to keep a city vibrant, effective and green.

Second, with the threat of resource constraints, particularly in energy, land and water, a pressing concern is to underpin all city planning processes with resource conservation, optimisation and recycling approaches. Fundamentally, closed loop processes must be advocated to minimise waste and raw material inputs. Waste-to-energy systems are promising options for further investigation. In land development, more compact city forms with a focus on urban revitalisation, brownfield regeneration and creative infills should take precedence over urban development on green field sites.

The third and perhaps the most critical urban challenge is to address the social divide to ensure that all residents have access to the benefits of urban development. Cities are the vehicles to promote social change and a better quality of life. Housing affordability and access to urban amenities are potentially the greatest social levellers. This is an area in which Singapore has developed significant insights that could be shared with other cities. Ultimately, cities are powered by people, and the primary aim should always be to build human-centred, sustainable communities for all.

Dr Malone-Lee is Director of the Centre for Sustainable Asian Cities, School of Design and Environment at the National University of Singapore (NUS). Prior to joining NUS, Dr Malone-Lee held senior positions in the civil service, working in the areas of strategic planning, planning policies and heritage conservation. Currently, her research interest is on urban planning policies and strategies for sustainable cities.