I just think that if the message of the environmentalists is going to be about changes in butterfly colors, you are going to have a difficult time galvanizing enough support to make a difference. The permian-triassic event is associated with a huge uptick in volcanic eruptions, or an asteroid hitting the earth, or something along those lines. No question that the ramifications of whatever happened resulted in warming the earth and greenhouse issues, etc., but I don't think there is any suggestion that the primary cause of that event was anything other than a colossal event as opposed to a general warming trend. A similar event would be something like a true nuclear war, or an asteroid event, or a dramatic uptick in volcanic eruptions.
Again, I think global warming is undeniable. I think it is undeniable that it is caused, at least in significant part, by man. I think it is a bummer that the salmon may die off. However, anyone who wants to create sweeping change is going to have to demonstrably show the negative, objective impact warming will have on mankind as a whole (or at least the US population specifically). Some people don't give a fuck about the salmon, and certainly aren't going to prioritize their lives around making sure the salmon's spawning grounds stay at a consistent temperature. It just won't register with enough people.
And, as you indicated - you believe humans will survive regardless. If that is the conclusion of even an informed, passionate environmentalist, then the chances for any radical change in behavior in the foreseeable future are slim to none.