Residents of a depressed neighborhood in the old part of Dhaka stand outside small shops on the banks of the Buriganga river on January 3, 2014. Photo: Getty Images

More than half of humanity now lives in cities, and even more will soon. The world will have to confront how to make cities more fit for human habitation.

Those are the conclusions of a report released Thursday by the United Nations, raising new challenges including cholera, classrooms and food production, reports The New York Times.

More than half world population now urbanized, @UNDESA reports http://t.co/Yj3KEICafN #OurCitiesOurWorld #WUP2014 pic.twitter.com/U0Zugf3C4v

— United Nations (@UN) July 10, 2014

If China urbanised most rapidly in recent decades, it is now India’s turn, thanks to a large bulge of young people in its population. Between now and 2050, India is projected to add 404 million people to its cities.

The Indian capital, Delhi, became the world’s second most populous city in 2014, more than doubling its population since 1990 to nearly 25 million. Mumbai is the other Indian megalopolis among the world’s 10 most populous cities, with 20.7 million people.

Salespeople sell their products at an open market in the busy streets of New Delhi's Shahjahanabad, the walled old city part of India's capital on March 31, 2014. Photo: Getty Images

Over all, India, China and Nigeria will account for 37 percent of the projected growth of the urban population between now and 2050, according to the report, World Urbanisation Prospects.

People wait to watch the annual Macy's fourth of July fireworks show looking over the East River on July 4, 2014 in the Brooklyn borough of New York City. Photo: Getty Images

Tokyo tops the report’s list of megacities, with a population of more than 37.8 million. Two cities in China are among the top 10: Shanghai (23 million) and Beijing (almost 20 million). Only one is in the United States: Taken together, New York and Newark, with a population of more than 18 million, rank ninth. None of the top 10 are in Europe. (The others are Mexico City, São Paulo, Osaka and Cairo.)

Major world cities home to most people, and another 2.5 billion inhabitants expected by 2050: http://t.co/iNzD0XVD7Z pic.twitter.com/1QuM2rE3E8

— Reuters Top News (@Reuters) July 10, 2014

By 2050, the vast majority of the world’s megacities will be in Asia, according to projections by the world body. New York is forecast to slip to 14th place.

The pace of urbanisation has been remarkably swift. In 1950, only 30 percent of the world’s people lived in cities. That has grown to 54 percent in 2014. By 2050, a full two-thirds of humankind will live in cities.

People march on a street during the annual pro-democracy protest on July 1, 2014 in Hong Kong. Photo: Getty Images

Close to half of them now live in small cities of less than 500,000 people. Only one in eight live in cities with more than 10 million people. There are 28 of these megacities around the world.

The overall numbers of rural inhabitants are projected to decline to 3.1 billion in 2050 from 3.4 billion today.