Can you run a city like a business?
9 June 2014 Last updated at 01:06 BST
For the first time ever, most of the world's population lives in cities.
A century ago, only two out of every ten people lived in urban areas. By 2050, that will increase to seven out of ten people.
The urban growth is expected to put huge stress on the world's infrastructure, food supplies and energy resources.
The BBC's Leisha Chi spoke to Arab Hoballah, the head of the Sustainable Consumption and Production Branch at the United Nations Environment Programme about the problem.
He explained why government officials should run their cities like a business.