Urban Greening
Of course the city has to have places to rest body and the eye, so trees and plants are installed and planted. I guess a gardener will not often think about allergies, since he then would probably not work in this field. So: besides of thinking about the impact of global warming, they could also think about allergy potential of plants. Then choose greening accordingly. I hear people more and more complain about feeling the pollens, so, maybe this would be a good step to do. Visually and because of the smell I mostly like fir trees. But this is optional.
I was thinking about how it would be to plant a lot of maple trees, so we could start to harvest maple sirup. They give the best sugar in my opinion. Hmm?