Stockholm — The rapid growth of urban population - described as one of the world's major demographic trends - has triggered an explosion of "mega cities" in Asia, Latin America and Africa, causing a breakdown in basic services, including water supplies and sanitation facilities.
And by 2050, about 70 percent of the world's population will live in urban areas causing horrendous problems, predicts a new 80-page study released here by the World Wildlife Fund (WWF).
The current world population of over 6 billion is expected to reach a historic high of 7 billion by the end of October, according to figures released by the U.N. Population Fund (UNFPA), which also estimates a figure of 9.1 billion for 2050.
As city infrastructure cannot keep pace with massive urban growth, many people will be left without adequate access to drinking water and sanitation, says WWF.
In most developing countries, urban growth is "inextricably linked" with slum expansion and poverty. In 2000, nearly one third of the world's urban dwellers lived in slums, the current figure is much higher.
The study focuses on six of the world's "exploding mega cities": Mexico City, Mexico, with a population of 21.1 million; Buenos Aires, Argentina, with a population of 12.8 million; Kolkata, India, with a population of 15.4 million; Karachi, Pakistan, with a population of 18 million; Nairobi, Kenya, with a population of 3.5 million; and Shanghai, China, with a population of 23 million.
Asked if growing socio-economic problems in mega cities could be a trigger for future social revolutions - as happened recently in the Arab world and during street riots in the UK - WWF's Martin Geiger told IPS: "No, I don't think water alone will trigger social unrest."
However, he pointed out, social unrest did take place in South Africa when a shortage of water led to protests in July 2009.
And in Cochabamba and La Paz, Bolivia, when people were not satisfied with water prices and deliveries, including problems relating to the installation of water metres and equity in distribution.
The issues involved in the "water wars" in Bolivia, that took place between January 1999 and April 2000, included price hikes and privatisation contracts with foreign investors.
Asked if big cities in developed countries could also face similar problems because of increased migration, Geiger said that major urban growth would primarily be in Africa, Asia and in some South American countries.
"Even with global migration, we don't see any major shift in this," said Geiger, director of WWF's Freshwater Programme based in Germany, stressing that, "it is difficult to foresee what will happen in 10 or 15 years from now."
Meanwhile, the WWF study, released here to coordinate with the 21st international water conference in the Swedish capital, paints a gloomy picture of the current situation in the six mega cities under scrutiny.
In the port city of Karachi in southern Pakistan, around 30,000 people die due to the effects of contaminated drinking water, while in Kolkata (formerly Calcutta), there are both traces of faeces in drinking water and high concentrations of arsenic in ground water.
The Chinese city of Shanghai, which has enjoyed good water access, is now facing water shortages and problems related to salination, according to WWF.
In the rivers of Buenos Aires, described as "public cesspits", there are high levels of dumped toxins making the Argentine river Matanza-Riachuelo "one of the world's most polluted waterways". And millions of people in the city lack safe access to drinking water and are not connected to sewer systems.
In Kenya, the capital city lacks capacity to manage the increasing demand for water. And 60 percent of Nairobi's inhabitants live in informal settlements with inadequate access to quality water and are forced to buy their water at kiosks at a higher price.
Additionally, says the study, the lack of access to sanitation results in untreated waste and wastewater not only endangering human health but also deteriorating the river systems.
In Mexico City, excessive overexploitation of groundwater has led to the sinking of the city over time by five to 10 centimetres. "The giant metropolis depends on pumping water from areas about 150 kilometres away," the study notes.
Anna Forslund, WWF's fresh water expert based in Sweden, said: "Rapid uncontrolled urbanisation is definitely a threat to the ecosystems we all depend on. We need better urban planning, efficient water use, and increased input from civil society."
The study makes a series of recommendations for future urban planning with regard to water sustainability, including innovative financing of water and wastewater infrastructure, an inventory of critical infrastructure at risk of flooding, droughts or sea-level rise, and the incorporation of green infrastructure and low-impact development.