London School of Hygiene & Tropical Medicine

A major study on cities, State of the World 2007: Our Urban Future, released today by the Worldwatch Institute to mark our transition to an urban planet, reveals that over half of the 1.1 billion people projected to join the world's population may live in under-serviced urban slums if global development priorities are not reassessed to account for urban poverty.

The report notes that while cities cover only 0.4 percent of the Earth's surface, they generate the bulk of its carbon emissions, making them key to alleviating the climate crisis. Cities from around the world have begun to take climate change seriously, many in response to the direct threat they face. Of the 33 cities projected to have at least 8 million residents by 2015, at least 21 are coastal cities that will have to contend with sea-level rise from climate change.

Dr Carolyn Stephens, Senior Lecturer at the London School of Hygiene & Tropical Medicine, is one of a number of global experts to have contributed to the report, which calls for renewed investment in education, healthcare and infrastructure in the world's cities. She says: 'Cities now represent the Brave New World, with a minority living long lives in over-consuming affluence, and where most die young in inescapable poverty. We cannot achieve either sustainable development nor human health for the majority with this unethical, unsustainable model of urban development'.

David Satterthwaite, Senior Fellow of the London-based International Institute for Environment and Development , who also contributed to the report, adds: 'Developing competent urban governments that work for their citizens within a broader framework of regional and global responsibility is one of the most pressing issues for the next 20 years.

'Cities provide many opportunities for combining high quality living standards with low resource use and waste generation. But this requires innovation, leadership and far more competent and accountable urban governments. Without this, cities become among the most polluted and dangerous places, where one in four children commonly die before the age of five'.

By sometime next year more than half of all people will live in urban areas. Over 60 million people-roughly the population of France-are now added to the planet's burgeoning cities and suburbs each year, mostly in low-income urban settlements in developing countries.

Unplanned and chaotic urbanization is taking a huge toll on human health and the quality of the environment, contributing to social, ecological, and economic instability in many countries. Of the 3 billion urban dwellers today, 1 billion live in 'slums', defined as areas where people cannot secure key necessities such as clean water, a nearby toilet, or durable housing. An estimated 1.6 million urban residents die each year due to lack of clean water and sanitation as a result.

The report describes how community groups and local governments have emerged as pioneers of groundbreaking policies to address both poverty and environmental concerns, in some cases surpassing the efforts of their national governments. 'The task of saving the world's modern cities might seem hopeless, except that it is already happening', says Christopher Flavin, President of the Worldwatch Institute.

The report calls on policymakers to recognise and address the urbanisation of poverty, and focuses on areas where urban leadership can have huge benefits for the planet and human development. These include:

• providing water and sanitation services to the urban poor
• bolstering urban farming
• improving public transport
• improving information gathering systems on urban issues