Urban gradening would be better in terms of the following reasons.
・It will contribute to reduction of carbon deoxide
・In tropical cities, it will cool down rooftop temperature, and then cause to reduce energy consumption by air conditioning
・plants will be grown more rapidly because of high concentration of carbon deoxide
But, because of narrow space, urban gradening tends to be less cost-effective. It means vegetable harvested in urban rooftop is not competitive with conventional vegetable from countryside.
The next stage that we have to think about would be how to reduce cost o grow vegetable in urbanized area.
