That's pretty cool.

Part of my reply to Vladimir addresses your question; I think [North] American farmers aren't all that oblivious, but I suspect that they are still more optimistic than they ought to be. 20 years also might be too short a time window; 50 years might be more appropriate, and the problem still remains.

If nothing else, psychology tells us that once we start talking about a 50 year time window, we should have a very high prior for people being overly optimistic and insufficiently discounting future costs.