How will cities need to change to accommodate future population growth?

Cities will need to grow vertically and to become much more self-sustaining.

Explanation:

The global population is growing and it is predicted to grow at least until the end of this century. Even more so, the population of cities is growing at an even faster rate, with people abandoning rural areas and towns and moving into the large urban areas. This has been, is, and will continue to be a huge problem when it comes to handling such a  big number of people living in a very small area.

In order for the large cities to respond to the challenge, they will need to take some measures. One thing that will help with space for living is the vertical growth of the cities instead of horizontal. This would be useful because much more people can live in a much smaller area without any problem, while also preserving valuable fertile soil and natural resources. Another thing that will need to be done is that the cities become as self-sustaining as possible. This would mean basically that the cities produce a large portion of their energy requirenments, every single place in the cities that can be used for growth and production of food to be used, be it the top of the buildings, yards/gardens, smaller spaces near infrastructure, and to have as much greenery as possible so that the city is more pleasant and healthier for living.