GREEN living environments can play an important role in making cities more equitable for their residents.

A number of cities in western Europe, the United States and Canada have pioneered green strategies.

Freiburg, a city of 200,000 inhabitants in Germany, has a long tradition of sustainable building and investment in recycling and it reduced CO2 emissions per capita by 12 per cent between 1992 and 2003.

Several cities in developing countries, especially in South America, have also branded themselves green. Authorities in Curitiba, Brazil, introduced policies to integrate land-use and transport planning and by the 1970s the city was equipped with an innovative bus rapid transit system.

Challenges for green cities include the rapid pace of urbanization and related pressure on the environment and social relations if it continues on the same trajectory.

Opportunities for green cities include the possibility to design, plan and manage their physical structure in ways that are environmentally advantageous, advance technological innovation as well as profit from synergies that exist between the constituent elements of complex urban systems.

In 2007, for the first time in human history, 50 per cent of the global population lived in urban areas. Only a century ago, this figure stood at 13 per cent but it is now predicted to reach 69 per cent by 2050.

In some regions, cities are expanding rapidly, while in others, rural areas are becoming more urban.

A significant part of this urbanization is taking place in developing countries as a result of natural growth within cities and large numbers of rural-urban migrants in search of jobs and opportunities.

Rapid urban growth tends to overwhelm cities where the struggle to develop infrastructure, mobilize and manage resources has negative consequences for the environment.

India and China

The scale of the problem comes into sharp focus in India and China.

India's urban population grew from 290 million in 2001 to 340 million in 2008 and it is projected to reach 590 million by 2030. The country will have to build 700-900 million square meters of residential and commercial space a year to accommodate this growth, requiring an investment US$1.2 trillion to build 350-400 kilometers of subway and up to 25,000 kilometers of new roads per year.

Similarly, China's urban population is expected to increase from 636 million in 2010 to 905 million by 2030. It is predicted that by 2050 the country will need to invest 800-900 billion yuan per year to improve its urban infrastructure, about one-tenth of China's total GDP in 2001.

The nature of this investment will have significant effects on the potential of Indian and Chinese cities to be green.

As cities become more prosperous, with wider and deeper patterns of consumption and production, their environmental impacts are increasingly felt at the global level.

Urban areas in prosperous economies concentrate wealth creation as well as resource consumption and CO2 emissions.

Globally, with a population share of just above 50 per cent but occupying less than 2 per cent of the earth's surface, urban areas concentrate 80 per cent of economic output, between 60 and 80 per cent of energy consumption, and approximately 75 per cent of CO2 emissions.

This pattern is not equally distributed across the globe and reflects the concentration of particular activities within individual cities.

Buildings, transport, and industry - which are constituent components of cities and urban areas - contribute 25, 22, and 22 per cent, respectively, of global greenhouse gas emissions.

Between 1950 and 2005, the urban population grew from 29 per cent to 49 per cent of the global population while global carbon emissions from fossil-fuel burning increased by almost 500 per cent.

At the national level, urbanization goes hand in hand with increasing resource consumption.

Cities per se are neither drivers of climate change nor the source of ecosystem degradation; certain consumption and production patterns as well as certain population groups within cities are.

The relationship between carbon emissions and income levels is not straightforward, either.

Per capita incomes are generally higher in cities than in rural areas, generating higher average per capita demand in major emissions sources.

But this is the case only up to a certain income level, after which cities typically become more carbon-efficient compared with the average, as can be seen by the relatively low levels of CO2 emissions produced by high income cities like Tokyo or Paris.

A recent survey of the energy intensity (a measure of the energy efficiency of an economy calculated as units of energy per unit of GDP) of 50 cities by the World Bank confirms differential patterns of environmental performance.

From this study, it appears that the combined energy intensity of major cities like Paris, Dhaka, S?o Paulo, London, Hong Kong, and Tokyo, amount to about one-quarter of that of the five highest scoring cities and less than half of a 50-city average.

In order to better understand these variations, data on 735 cities in six regions were analyzed. The results show that a majority of cities in Brazil, China, South Africa, India, Europe and the United States cities outperform their national average in terms of income per capita, education and employment levels.

In terms of carbon emissions, energy, electricity and water consumption, dwelling and transport patterns and motorization, however, there is a very marked difference between cities in developed and developing countries.

Whereas cities in Europe, the US and Brazil have a lower environmental impact than their respective countries, cities in India and China have a much larger impact owing to their significantly higher income levels compared with their national averages.

Patterns of urbanization in many areas also raise important social challenges. The traditional business-as-usual model of urban development - typical of many rapidly urbanizing areas - is characterized by uncontrolled horizontal expansion leading on one hand to urban sprawl of affluent populations with lower development densities and increased dependency on the private car and on the other hand to the peripheralization of the urban poor, decreasing their access to the city and its workplaces, services and infrastructure.

Typical developments further include the emergence of socially divisive neighborhoods in the form of gated communities, shopping centers and business districts and, a significant increase in the level of informal development with large swathes of slum housing with no access to basic services, infrastructure and sanitation.

At a general level, the rapid growth of many cities coupled with insufficient resources and poor management compromises fresh water and electricity supply, waste treatment, transport, and other infrastructure provision, affecting the urban poor most.

Cities can be designed, planned and managed to limit resource consumption and carbon emissions.

Or, they can be allowed to become voracious, land-hungry, all-consuming systems that ultimately damage the delicate global energy equation.

More compact urban forms, reduced travel distances and investment in green transport modes lead to greater energy efficiency.

In short, effective urban planning and governance can have significant effects on sustainable urban lifestyles, making the most of urban critical mass and reducing individual patterns of consumption.



This article is adapted from a recent UN Environment Program report on green economies.