With more than 1 billion people living in urban slums, the United Nations today marked World Habitat Day with calls for major government action to prevent the scourge from doubling in the next 30 years.While this year’s slogan – Cities magnets of hope – highlights the important status of cities as refuge for the displaced and home to expanding populations in search of a future, Secretary-General Kofi Annan emphasized that they can also be places of considerable despair.“Never before has the world witnessed such a large proliferation of urban slums,” he said in a message, stressing that 6 billion people, or two-thirds of humanity, will be living in towns and cities by 2050. “Today, 1 billion people, or 1 of every 3 urban dwellers, live in slums. If municipalities and governments fail to manage urban growth and migration sustainably, this number is expected to double in the next 30 years.“Almost everywhere, cities are the destinations for people escaping poverty, conflict and human rights violations, or simply those looking for ways to build better lives,” he added, noting that major cities such as Dakar, Jakarta, Johannesburg or Rio de Janeiro are having trouble accommodating new migrants while so many long-standing citizens are still struggling. The Executive Director of the UN Human Settlements Programme (UN-HABITAT), Anna Tibaijuka, launched this year’s celebrations in Naples, Italy, where she stressed that cities have to be able to provide inclusive living conditions for all their residents, rich or poor, with a decent living environment, clean water, sanitation, transport, electricity and other services.“How we manage this is arguably one of the greatest challenges facing humanity,” she said, calling for the protection of the human rights of trans-border migrants and warning that inner city slums or “ethnic” ghettoes can become hotbeds of social unrest and civil strife, as recent events in Europe have shown.The UN Environment Programme (UNEP) emphasized the considerable ecological impact of urban growth with the prolific use of natural resources, generation of waste and production of most of the greenhouse gases causing global climate change.“They often degrade local water quality, deplete aquifers, pollute the marine environment, foul the air and consume the land, thereby devastating biological diversity,” it said in a statement.“Creating environmentally friendly cities is admittedly a big challenge, but the technologies and expertise we need already exist. Clean transport, energy-efficient buildings, safe sanitation and economical water use are possible now, not just in the future, often in a manner that is affordable for all.”The UN Special Rapporteur on adequate housing, Miloon Kothari, called for “a holistic approach” that includes addressing the cause of rural migration to the cities.“Such migration is generally not voluntary but a result of the loss of hope in rural areas, the loss of means of subsistence resulting from a lack of priority to agrarian reform, growing landlessness and indebtedness, failure to promote rural infrastructure, displacement induced by large projects, distressed housing conditions, or the state and corporate takeover of farmland for industry,” he said in a statement.