"Ecosystems are always changing at the landscape level, but normally the rate of change is too slow for humans to notice," said Steven Running, the University of Montana Regents Professor and a co-author of the study. "Now the rate of change is fast enough we can see it."
Even though the rate of change has increased, these processes will take time, the scientists said. A greater stability of forest composition will not be attained anytime soon, perhaps for centuries.
"There's not a lot we can do to really control these changes," Waring said. "For instance, to keep old trees alive during drought or insect attacks that they are no longer able to deal with, you might have to thin the forest and remove up to half the trees. These are very powerful forces at work."
One of the best approaches to plan for an uncertain future, the researchers said, is to maintain "connective corridors" as much as possible so that trees can naturally migrate to new areas in a changing future and not be stopped by artificial boundaries.