Some African countries are 'urbanizing before they industrialize' - and it could be devastating for future populations

Over the next 35 years, the United Nations predicts that 2.5 billion people will move into cities.

Some of those cities already have the necessary infrastructure, like bridges, hospitals, and office buildings, to support that influx. China, for instance, is moving 250 million people into its budding megacities over the next eight years. It's been quickly building highways and roads for the last couple decades.

But not all countries are building infrastructure fast enough to support populations, as urban planning expert Robert Muggah, Research Director of the Igarapé Institute, has noted. Many African countries face high unemployment, crime, and violence, in conjunction with rapidly-growing populations in urban areas. Muggah says this creates "fragile" cities that become vulnerable to economic and social collapse.

Here's how the vulnerable regions got to where they are, and what they could do to minimize those risks for future populations.