Root at roof
In the future cities we will be luck of the space and land.

Solution

In the future cities we will be luck of the space and land. And we will have to find other ways to grow vegetables, and food. Every roof may be turned in the garden. So in the every building may exist a sort of farm, and somebody who is working there and taking care of plants. Everybody will be available to buy freshly picked/harvested herbs in their own building. Plants cultivated that way will not use soil to grow, some of them may be set upside down. In that way they may lay in layers while root will be carefully connected with source of water with all nutritient they need. Sistem will be well controled and balanced.

Future of feeding also will go in directon of better control how much and what we eat. Food allergies are more often, and we should check all allergens at the beggining of our lives. So do diet should be balanced, and everybody will have some gadget that can control needs and what we should eat to have enough mineral and nutrients.

So, future people will take their gadget and go to roof, and by what they need for that day.