If all cities and above ground homes were dismantled how many people could live on earth underground?

I'm thinking that likely the earth might support 13 to 14 billion people if all cities and homes and buildings above ground were disassembled completely and we all lived underground instead.

Why?

Because when you give all the land back to potential farming and recreation and parks then you increase the land that is tillable.

For example, in places like California where some of the best soil is on earth in places like the Salinas Valley and the San Joaquin and Sacramento Valleys you have people building homes and cities over the best farmland on earth which is sort of ridiculous when you think about it because of all the starving people now on earth.

But, in the end it is all a choice we all make by whatever choices we choose to make or not make ongoing.

So, one of the ways to support life on earth is to move underground thereby opening up more tillable land for everyone everywhere.

This solves another problem which is heating and cooling because often underground temperatures (below about 2 feet under the earth) stay pretty constant around 55 to 65 degrees Fahrenheit most places. So, once you use the earth as insulation, heating and cooling is much less of a problem than before. However, you still need fresh air in order to stay healthy and you still need sunlight to stay healthy too over time. also light could be reflected down into underground facilities through mirrors if people wanted to during the day times too.

But, imagine how much more tillable land there would be to grow food or for recreation if no more homes or businesses were built above ground anymore and we started tearing down cities to make that land tillable again too?

So, basically what would be above ground?

Likely roads (unless we all traveled by air or water most of the time) and green places and deserts and mountains and plains. So, traveling would be beautiful a lot of the time without factories and cities spoiling the landscapes. Then there would only be the countryside and farms and national parks and mountains and oceans and lakes and rivers around the world.


But, you don't want to be living underground in a flood plain for example, unless you are living in some sort of submarine capable of dealing with that during flooding of your area. But I suppose some people might like living in a submarine especially if they once served in the Navy on a submarine and got used to it.

So, more likely you are going to see people living underground on the sides of hills and mountains outside of flood plains where they might just have one glass wall looking out from a hill or mountain and three walls underground.

There are all sorts of ways to do this and people have been experimenting with ways to do this for thousands of years already all over the world.

You especially see that living underground is useful in places where it gets very hot in the summers like in deserts where it can still stay cool underground while temperatures might be in the 100s Fahrenheit during the summers in the day time there.

But, also in places very cold living underground is equally useful because it doesn't take very much to heat a facility underground either especially if it is under 2500 square feet in floor space.