The world's mega-cities are merging to form vast "mega-regions" which may stretch hundreds of kilometres across countries and be home to more than 100 million people, according to a major new UN report.

The phenomenon of the so-called "endless city" could be one of the most significant developments - and problems - in the way people live and economies grow in the next 50 years, says UN-Habitat, the agency for human settlements, which identifies the trend of developing mega-regions in its biannual State of World Cities report.

The largest of these, says the report - launched today at the World Urban Forum in Rio de Janeiro - is the Hong Kong-Shenhzen-Guangzhou region in China, home to about 120 million people. Other mega-regions have formed in Japan and Brazil and are developing in India, west Africa and elsewhere.

The trend helped the world pass a tipping point in the last year, with more than half the world's people now living in cities.

The UN said that urbanisation is now "unstoppable". Anna Tibaijuka, outgoing director of UN-Habitat, said: "Just over half the world now lives in cities but by 2050, over 70% of the world will be urban dwellers. By then, only 14% of people in rich countries will live outside cities, and 33% in poor countries."

The development of mega-regions is regarded as generally positive, said the report's co-author Eduardo Lopez Moreno: "They [mega-regions], rather than countries, are now driving wealth."

"Research shows that the world's largest 40 mega-regions cover only a tiny fraction of the habitable surface of our planet and are home to fewer than 18% of the world's population [but] account for 66% of all economic activity and about 85% of technological and scientific innovation," said Moreno.

"The top 25 cities in the world account for more than half of the world's wealth," he added. "And the five largest cities in India and China now account for 50% of those countries' wealth."

The migration to cities, while making economic sense, is affecting the rural economy too: "Most of the wealth in rural areas already comes from people in urban areas sending money back," Moreno said.

The growth of mega-regions and cities is also leading to unprecedented urban sprawl, new slums, unbalanced development and income inequalities as more and more people move to satellite or dormitory cities.

"Cities like Los Angeles grew 45% in numbers between 1975-1990, but tripled their surface area in the same time. This sprawl is now increasingly happening in developing countries as real estate developers promote the image of a 'world-class lifestyle' outside the traditional city," say the authors.

Urban sprawl, they say, is the symptom of a divided, dysfunctional city. "It is not only wasteful, it adds to transport costs, increases energy consumption, requires more resources, and causes the loss of prime farmland."

"The more unequal that cities become, the higher the risk that economic disparities will result in social and political tension. The likelihood of urban unrest in unequal cities is high. The cities that are prospering the most are generally those that are reducing inequalities," said Moreno.

In a sample survey of world cities, the UN found the most unequal were in South Africa. Johannesburg was the least equal in the world, only marginally ahead of East London, Bloemfontein, and Pretoria.

Latin American, Asian and African cities were generally more equal, but mainly because they were uniformly poor, with a high level of slums and little sanitation. Some of the most the most egalitarian cities were found to be Dhaka and Chittagong in Bangladesh.

The US emerged as one of the most unequal societies with cities like New York, Chicago and Washington less equal than places like Brazzaville in Congo-Brazzaville, Managua in Nicaragua and Davao City in the Phillippines.

"The marginalisation and segregation of specific groups [in the US] creates a city within a city. The richest 1% of households now earns more than 72 times the average income of the poorest 20% of the population. In the 'other America', poor black families are clustered in ghettoes lacking access to quality education, secure tenure, lucrative work and political power," says the report.

Cities are pushing beyond their limits and are merging into new massive conurbations known as mega-regions, which are linked both physically and economically. Their expansion drives economic growth but also leads to urban sprawl, rising inequalities and urban unrest.

The biggest mega-regions, which are at the forefront of the rapid urbanisation sweeping the world, are:

• Hong Kong-Shenhzen-Guangzhou, China, home to about 120 million people;

• Nagoya-Osaka-Kyoto-Kobe, Japan, expected to grow to 60 million people by 2015;

• Rio de Janeiro-São Paulo region with 43 million people in Brazil.

The same trend on an even larger scale is seen in fast-growing "urban corridors":

• West Africa: 600km of urbanisation linking Nigeria, Benin, Togo and Ghana, and driving the entire region's economy;

• India: From Mumbai to Dehli;

• East Asia: Four connected megalopolises and 77 separate cities of over 200,000 people each occur from Beijing to Tokyo via Pyongyang and Seoul.

http://www.guardian.co.uk/world/2010/mar/22/un-cities-mega-regions 

Robert Harrison has been able to send his £500 device 22 miles above the earth's surface - a height that can only be reached by a rocket or weather balloon.

Over the last two years, the IT director from Highburton in West Yorkshire has launched 12 high-altitude balloons with a simple Canon camera attached.

Mr Harrison stumbled on the idea when he tried to take aerial photographs of his house using a remote control helicopter.

When his experiment failed, he started to look into high-altitude weather balloons on the internet, launching his first device - Icarus I - in 2008.

He programmed the camera, using free software downloaded from the internet, to take eight photos and a video every five minutes before switching into standby mode.

Mr Harrison, 38, uses GPS tracking technology to monitor the camera as it automatically parachutes back to earth after reaching the 22-mile high mark.

The pictures are so impressive that Nasa has reportedly been in touch, telling the father-of-three it would have spent millions to get the same results.

"A guy phoned up who worked for Nasa who was interested in how we took the pictures," Mr Harrison told The Times newspaper.

"He wanted to know how the hell we did it. He thought we used a rocket. They said it would have cost them millions of dollars."

Doctors had to put Valerie Leah into a coma and deliver her son Oliver three months early in order to save her life.

Mrs Leah and her son, who weighed just 2lb 10oz when he was born, then spent months in intensive care at Tameside General Hospital in Greater Manchester.

But four months on, both have recovered and doctors believe they may be the first mother and child to survive such a complex case of swine flu during pregnancy.

Baby Oliver still weighs just 6ib 9oz but the hospital has given him the all-clear.

Mrs Leah, 35, from Mossley, said: "He is a gorgeous baby, he is really chilled out, really happy, we are so happy to have him at home.

"He is so tiny everyone thinks he is a newborn - they are stunned when I tell them he is four months old."

Mrs Leah, contracted the H1N1 virus last November, along with husband Simon and their other children Ben, 10, and five-year-old Lewis.

The mum-of-three developed an air leak in her lungs and needed a special form of ventilation which can only be given to a patient lying face down - impossible while she was heavily pregnant.

After she was put into a medically-induced coma, Oliver was born by caesarean section and cared for in the hospital's special care baby unit.

The staff kept a daily diary for him so his mother would know what had happened to him while she was ill.

Oliver was two weeks old before Mrs Leah met him for the first time.

"He looked really sick," she said, "He was tiny. It was very difficult and I felt very weak, very weepy anyway."

Oliver was very poorly and had to overcome two infections, remaining in hospital until the end of February before being allowed home.