This looks to me like it's just to keep some distance between the cranes and the construction. I could be wrong, but that fence certainly looks like it's just a temporary barrier.
@ZooElephantMan, the far side is all of the space currently accessible to the cranes.
@Neil chace, that I what I assumed as well. It is definitely not a permanent barrier. Because of the visibly newer fencing in both pictures, I'm thinking that the red panda building will eventually be a barrier for the crane enclosure on that side.
