I used to visit some greenhouse farming farms, and as the OP mentioned, I found that in the case I visited, it was simply a locality that was not suitable for farming such as farming rice, corn, potatoes, ... but mainly clean foods are green vegetables and fruits. I think the problem of agricultural diversion has not only just begun, but people have also seen the dangers of land shortage or climate change for future solutions, there are friends of mine right in the city. People in the city also have a sense of self-sufficiency about growing their own vegetables in their own homes, just a few cardboard boxes and providing them with enough water, light, fertilizer, ... they also have can partially solve the household food story.