Ooh, what you have there is an interesting point..
1: Plant more cannabis
2: reduce C02 stuffs, as plant like to use it to produce energy.
3:Everyone gets high, as its now legalised to, less wars are fought.
4: ?????
5: Profit!
I like the idea, but since we would be burning it after anyways, then it might not turn out to be so beneficial.
Still has to be better than the current situation.