(CNN) The coming decades will see the growth of colossal megacities as the world's population increasingly moves into urban environments, a new United Nations report predicts.

Today, 55% of the world's population is urban, a figure which is expected to grow to 68% by 2050, with the addition of 2.5 billion new city residents, according to projections by the Population Division of the UN Department of Economic and Social Affairs.

By 2030, there will be 43 megacities around the world with populations of over 10 million, up from 33 similarly sized urban centers today and just 10 in 1990.

The growth is caused by an accelerating shift from rural to urban living across the world, particularly in Asia, which despite hosting some of the world's largest cities has lagged behind other parts of the world in terms of overall urbanization.

In Asia, approximately 50% of the population live in cities, compared to 82% in North America, and 74% in Europe. Africa is the least urban populated continent, with just 43% of its population living in cities.

Read More