We are living in the midst of the urban century. Though it is common knowledge that the world is urbanizing, it can be striking to visualize this growth on a map. This animation from Unicef maps countries’ urban populations from 1950 to 2050, and shows that urbanization is a global phenomenon set to continue for decades:

As seen in the animation, a number of African countries will go from less than 25% urban in 1950 to more than 75% urban in 2050. From 2010 to 2050, Nigeria’s urban population will nearly triple from 79 million people to 218 million. But this growth pales in comparison to the transformative urban growth occuring in Asia. As shown by the map below, much of the world’s population is concentrated in Asian countries:

Asian countries are undergoing a century-long rural to urban migration. Unicef’s animation shows that in 1980, both India and China were less than 25% urban, with 160 and 190 million people living in cities, respectively. By 2050, India and China will both be more than 50% urban with staggering urban populations of 875 million and 1.04 billion, respectively.

Some of this urban growth is concentrated in megacities

According to the United Nations, there were ten megacities with ten million people or more in 1990. Today there are 28, and by 2030, they estimate that there will be 41. This map from Statista shows that the top 15 megacities will absorb a striking number of new residents over the next decade. For example, between 2011 and 2025, Dhaka, Bangladesh is set to grow by eight million people, and New Delhi is expected to add ten million.

As they grow in population, many of the world’s biggest cities have rapidly growing urban footprints. This visualization of Lagos, Nigeria, for example, shows the city’s geographic expansion, which has accelerated in recent decades:

In some parts of the world, cities’ growing urban footprints and rising populations are creating an urban region of clustered cities – called a megalopolis. For example, in China’s Pearl River Delta, nine cities are becoming a megalopolis that covers 16,000 square miles.

In 2012, The Guardian reported that planners will spend £190 billion (US$ 296 billion) until 2018 integrating transport, energy, water, and telecommunications services among the region’s cities. Including the special administrative zones of Hong Kong and Macau, this cluster of urban areas has over 60 million people.

Rapid growth is also happening in smaller cities

The world’s urban growth is not limited to megacities. In countries worldwide, small- to medium-sized cities are also in the midst of rapid expansion, as shown by this chart from the United Nations:

How can we deal with the world’s urban growth?

Urban growth – particularly in megacities – can create distinct challenges including housing shortages, air pollution, congestion, and more. However, well managed growth can help create sustainable, livable urban communities. A growing consensus is emerging around the science of people-oriented cities that are connected by sustainable transport, compact, and coordinated through effective governance. Ensuring that cities can be equitable, sustainable, and livable will be the defining challenge of the urban century.