I think that the concept of vertical gardens is really underutilised considering how desperately we need to be sequestering CO2 from the atmosphere, and considering the issue that land-use is. If local councils would start planting vertical gardens, or even climbers up the sides of buildings etc, I think this could have a real impact. Particularly considering the indirect effects - for example the plants helping to keep cities cool. The feel of being around nature is also proven to be good for peoples' mental health. And of course, it would look nice. My idea is for everyone (governments, councils, individuals) to start getting around the little things we can do to make a difference. When we all do a little thing, it can have big effects.