Vertical farming is a new concept. By growing crops indoors under lights, the crops grow far faster and so can be harvested multiple times a year. Furthermore, by using artificial lights it is possible to have many layers of food.
A new study has found that using a 10 layer indoor vertical farm, yields could be between 220-600 times that of current methods. Given we currently have 1.7 million hectares of wheat (this is 6500 square miles), we could reduce this to just 28 square km of these buildings.
It suggests that we could allow far more of the UK land to return to a more natural state (or indeed use it for a different purpose). One issue, is that it is very energy intensive which means that until the price of energy falls it would not be financially competitive though if we fully engage in Solar and wind, that could change fast.