Jonah Hansen: Rooftop forests are the future

Whenever I fly above Salt Lake City and look out at all the blank and boring rooftops in the valley, I wish there was something better to do with that empty space.It turns out there is. And it might just save us.If each rooftop were a forest, no one would even be able to spot where the mountains end and the city begins. Everyone who flies into the Wasatch Front would be amazed by the greenery and the hidden civilization beneath it.Rooftop forests would be tree gardens installed on the top of dep