The fact that we are still facing this waste resources and pollution problem terestrially and now in space kind of gives you the notion that it will be an awful long time before we are truly ready to venture out further and colonise other worlds, naturally or artificially created, without leaving a trail of destruction behind us.
I wonder if aliens, if they exist, have become extreme recylclers throughout their evolution and are much more biologically efficient in order to help them adapt and survive the rigours of survival itself?