That's a good question.
I think the big wild cards in that equation centre around climate change for sure, because I think we've yet to see how their impacts are going to play out. The mountain pine beetle is a really good example of that. Native species--no one would have guessed that if you change the temperature regime slightly, this thing can go crazy and eat half of central British Columbia and maybe move across to the boreal. That is a huge wild card. And there are other factors besides: changes in insect outbreak or fungus or bacteria that could have an impact on forest health and our ability to extract forest resources.
Given that we know we're going to have significant climate change and that some of these ecosystem impacts we haven't foreseen are going to occur, we need to be managing our forests in a way that creates resilience. There has been a lot of discussion of this in British Columbia. The chief forester in British Columbia has talked pointedly about the need to move forest management there to one that is much more cautious to be able to maintain a harvest level and wood flow in products and community benefits that can be sustained in the face of a high degree of uncertainty because of climate change.