When you run out of land in a crowded city, the solution is obvious: build upwards. This simple trick makes it possible to pack huge numbers of homes and offices into a limited space such as Hong Kong, Manhattan or the City of London. Mankind now faces a similar problem on a global scale.
The world's population is expected to increase to 9.1 billion by 2050, according to the UN. Feeding all those people will mean increasing food production by 70%, according to the UN's Food and Agriculture Organisation, through a combination of higher crop yields and an expansion of the area under cultivation. But the additional land available for cultivation is unevenly distributed, and much of it is suitable for growing only a few crops. So why not create more agricultural land by building upwards?
Source: https://www.economist.com/node/17647627/all-comments
Watch this video to find out more: