Many eminent people are suggesting to take up the rooftop agricultural activities.  I have analysed the reasons as follows :
1. The Industrialisation and commercialisation had depleted the quantity of Agricultural lands. The same has to be reinvented.
2. on the other hand, due to the urbanisation, the rooftop space availability has increased . The same has to be utilised.
3. Presently, there is a lot of emphasis on the health consious. But, people are not aware whether the vegetables are free of pesticides and fertilisers. To harvest the fresh vegetables,  rooftop  agricultural is required.
4. As the population is growing,  there is need to discover new lands and new methods  ( horizontal / vertical ).
5. It creates the cooler atmosphere in the surroundings.
6. The release of oxygen,  control of carbon dioxide,  containing pollution,  Global warming, etc. are remain same like other trees and plants does it.
7. Availability of fresh and nutritional foods are similar to that of kitchen gardens.

Pictures are showing the methods existing in the rooftop agricultural.