Over the last two decades, demographic and economic changes have propelled cities and urban centres to become the principal habitat of humankind. Cities are not only where rapid improvements in socio-economic and environmental conditions are possible, but it is, indeed, where such change is most needed. The cities of the world's emerging economies are increasingly drivers of global prosperity while the planet's resources are fast depleting. It is, therefore, more critical than ever that Member States and United Nations agencies commit themselves to realize the goal of sustainable urbanization as a key lever for development.

We must urgently find ways to achieve economic and socially equitable growth without further cost to the environment. Part of the solution lies in how cities are planned, governed, and provide services to their citizens. When poorly managed, urbanization can be detrimental to sustainable development. However, with vision and commitment, sustainable urbanization is one of the solutions to our ever growing global population. Efforts to create jobs, reduce our ecological footprint, and improve quality of life are most effective when pursued holistically. By prioritizing sustainable urbanization within a broader development framework, many critical development challenges can be addressed in tandem such as energy, water consumption and production, biodiversity, disaster preparedness and climate change adaptation. It is vitally important that this emerging opportunity be recognized and endorsed at Rio+20.


The effects of urbanization and climate change are converging in dangerous ways. The world's population is already more than 50 per cent urban and this is expected to rise to two-thirds in little over a generation. Cities and towns already bear the brunt of natural disasters such as flooding and tropical storms. Many of the world's largest cities and towns are located along coastlines, rivers, and floodplains which are most vulnerable when natural disasters strike.

Forecasts based on the best available scientific evidence indicate that in the coming decades, climate change may render hundreds of millions of urban residents increasingly vulnerable to floods, landslides, extreme weather and other natural disasters. Increasingly, the poorest and most marginalized are disproportionately affected and yet they have the least capacity to mitigate against these impacts and protect themselves. For example, research in UN-Habitat's* most recent State of African Cities Report suggests that as many as 200 million Africans could be displaced by the effects of climate change by the year 2050, putting a huge strain on the capacity and resources of cities. Asia is also far from immune to the effects of climate change. For example, in the 2011 floods in Bangkok, Thailand, more than 500 people lost their lives and exponentially more suffered significant losses to their livelihoods. While all coastal cities face such threats, the impact on those with populations of over 10 million inhabitants will be substantial. It is estimated that, without extensive adaptation efforts, a 1-metre sea level rise in New York could not only inundate coastal areas, but have a devastating impact on the subway system, sanitation facilities, power plants and factories, thereby affecting the economy of the city.

Without appropriate planning, design, and investment in the development of sustainable cities, a growing number of people will continue to face unprecedented negative impacts, not only of climate change but also of reduced economic growth, quality of life, and increased social instability.


In addition to experiencing the effects of climate change, cities disproportionately contribute as much as 70 per cent of the world's greenhouse gas emissions, although they occupy just 2 per cent of the land area. Intensified human activity in cities has led to increased greenhouse gas pollution while the capacity of oceans and vegetation to absorb them is declining. The urban ecological footprint in both developing and developed countries is on the rise with the increasing use of fossil fuels for transportation and construction, large-scale industrial pollution, deforestation, and land use changes, among others.

Affluence and increased demand for global services and products contribute to increasing environmental pressures. Lifestyle and consumption choices are profoundly changing the size, structure, and density of cities. While some cities in the developed countries are shrinking, many urban centres in developing countries are experiencing rapid and largely uncontrolled population growth. This means that the demand for housing, basic urban services, and consumer goods are growing. A preference for suburban living has a negative impact on both rural and urban environments alike, as it disadvantages public transport and creates severe traffic congestion contributing to greenhouse gas emissions.

To fully understand how urban centres contribute to climate change requires an understanding of how transport, buildings, heating and cooling systems, industries and other urban activities act as emitters and directly cause climate change. The geography, climate, spatial form, and economic base of a city significantly shape energy use patterns and greenhouse gas emissions.


We have the science and know-how to tackle many of these problems and significantly reduce root causes of climate change -- from the fossil fuels used for electricity generation, transport, and industrial production, to waste disposal and changes in land use. It is here that cities can make a difference by effectively and collectively addressing these challenges.

Cities represent the greatest achievements of human civilization. Throughout history they have served as centres of scientific research and innovation, solving some of our most pressing concerns. Cities offer a largely untapped opportunity to develop cohesive mitigation and adaptation strategies to deal with the risks associated with climate change and lessen their impact on the environment.

To be effective, such strategies must be integrated into urban planning frameworks. This is easier said than done. Cities are perhaps humanity's most complex creation. To address our collective infrastructure, mobility, energy, housing, water, and waste management needs, we must develop a new paradigm to work across artificial institutional silos and sectorial concerns. As a former mayor, I often marvelled at how easily professionals lose sight of the fact that the people we serve live profoundly integrated lives. Our challenge is to respond with equally integrated environmental, economic, and culturally sensitive responses. Without a doubt, cities can provide a unique opportunity to positively mitigate the impacts of climate change.

Several hundred cities are already taking action. Promising examples include Austin, Chicago, Durban, Hamburg, Maputo, Mexico City, Nantes, São Paulo and several cities in China, Korea, and the Philippines. UN-Habitat's Cities and Climate Change Initiative is currently supporting cities in 20 countries in Africa, Asia, and Latin America to develop and implement climate action plans. Undoubtedly, these are important steps in the right direction, but only a collective effort on a global scale will be commensurate to the task at hand.


Aside from their obvious environmental impacts, cities are unquestionable engines of economic growth and account for as much as 80 per cent of gross domestic product. Cities provide employment and distinct opportunities for poverty eradication. To date, no country has achieved high standards of living for its citizens without urbanizing. While many have tried, no country has been able to successfully halt or reverse the trend of urbanization. Climate friendly urban planning and design are not only necessary for the security of a city's inhabitants but also recognize the need to protect a country's most important economic assets. Protecting infrastructure and services safeguards livelihoods and enables economic activity to flourish.

Cities need to be planned, designed, and developed to lessen their impact on the environment, be resilient to the effects of climate change, and contribute to economic growth. Compact cities, with well designed services and infrastructure, reduce the cost of energy provision, transport, and other services that businesses need. This, in turn, increases productivity and efficiency, and encourages private investment for economic growth.

The green economy presents new opportunities for shared prosperity. It will not only contribute to achieving the Millennium Development Goals such as poverty eradication, food security, sound water management and sustainable cities, but it can also provide stimulus for employment and development.

Communities, businesses, and local authorities must be recognized as essential players in developing and implementing national and city-level climate change strategies and socio-economic development. From playing a marginal role within climate change frameworks and funding mechanisms, we must today seize the opportunity and harness the potential of cities to realize a sustainable future for all.

*UN-Habitat is the United Nations Programme for human settlements tasked with promoting the sustainable development of cities and towns through comprehensive urban planning.