"For the first time in human history, more of the world’s 6.8 billion people live in cities than in rural areas. That is an incredible demographic and geographic shift since 1950 when only 30 percent of the world’s 2.5 billion inhabitants lived in urban environments.
The world’s largest cities, particularly in developing countries, are growing at phenomenal rates. As a growing landless class is attracted by urban opportunities, meager as they might be, these cities’ populations are ballooning to incredible numbers.
A May 2010 Christian Science Monitor article on “megacities” predicted that by 2050, almost 70 percent of the world’s estimated 10 billion people—more than the number of people living today—will reside in urban areas. The social, economic and environmental problems associated with a predominantly urbanized population are considerably different from those of the mostly rural world population of the past."