It’s liberal fantasy math. It doesn’t have to make sense. Nor does the author need to know anything about agriculture. If people can figure out how to make the economics of this work out, however, it would be great. Nothing wrong with finding an adaptive use for otherwise dead space. But this is New York. I thought all the rooftops were going to have solar panels and wind turbines.
They should plant crops on the solar panels and on e blades of the wind turbines. That should work.