2300 Jet liners parked 'cause of Great Depression II

Aviation Week has a graph of grounded (parked and retired) airliners going back to 1989. Pretty steady rise from 400 in 1989 to 2300 today. The post 9/11 peak was only 2100. Two questions. What can you do with elderly airliners? How can Boeing's backlog of almost 900 orders for the 787 hold up with 2500 old but flyable planes sitting in the Arizona desert for cheap?