By Nilanjana Sen for Fair Observer.

With over half the world’s population living in cities, the 21st century has been described as the urban century. It is estimated that 75% of the global population will be living in cities by 2050.

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The first urban settlements appeared as early as 3,000 BC in ancient Mesopotamia, Egypt and the Indus Valley. Historically, cities have fulfilled various functions ranging from sites of pilgrimage, centers of trade and providing protection against enemies.

Today, even as cities cover less than 2% of the Earth’s surface, they consume 78% of the world’s energy.

During the Industrial Revolution, cities developed a more prominent commercial function, attracting people from rural areas who moved to the metropolis in hope of benefiting monetarily from this shift. The urban population share in England increased from 25.9% in 1776 to 65.2% in 1871. In the early 19th century, this was due to immigration that was largely local in nature, but at the turn of the century natural increase was a major factor in shaping population growth.