What it does not account for is the impact on ecosystems.
Accelerated erosion can change the environment too rapidly for organisms to adapt.
What you may also not be aware of is that the tree hugger, hiker, organizations are much more involved with land preservation which is how the parks get created in the first place. I really don't think that they are being selfish but rather protective of the land that they worked hard tp preserve. Maybe you have confusion in the difference between an advocacy group and race promotion. Yes, each of us must be part-time advocates, but there are efforts involved that are full time jobs and it is great that someone is willing to live with less pay, and devote their lives just to help you have someplace to ride.