It would need to be put in the context of what a normal annual die-off is. I expect it's not 0%, and perhaps it's normal for keepers to need to re-establish some fraction of their hives each year.

Of course, 50-60% sounds alarmingly high, but I don't know enough to be sure.

Actually, I just followed the link in the article (good job detailing their sources!) and it looks like 40% is pretty typical, but with large error bars. 62% is definitely high, but not as earth shattering as it first appears.