I'm thinking of a bunch of other cool side effects of this. If we plant really tall buildings we get a different elevation and possibly a different environment and ecosystem. Can we plant rainforests up there? If we plant enough roofs we might be able to get a totally new and independent ecosystem. Most of the roofs are not accesible to the public.
I'm thinking "Lost World of Roi Rama!" Anyone up for an expedition in the future?
Addition by Author: Rainforests have very poor and shallow soil so I suspect the trees have shallow roots, which would work for the rooftops (hate to see the CEO's desk pierced with a tree root in the middle of a board meeting). I also just found out that Kenosha, WI (Wisconsin, not West Indies) has green roofs that they populated with sheep! How cool is that! Next they'll have to put wolves or coyotes up there to cull the herds. Oo I feel so many stories a-brewin'.