I must have forgotten what I learned in biology but I always thought a herd of 500,000 animals should start the year off with about 250,000 offspring. This is out in the remote tundra. The herd migrates every winter closer to where SOME of the native hunters have access to them. Other predators aside, that would mean those few hunters, even if they are taking more than what you or I could harvest, would have to take at least a number equivalent to the years offspring before the herd declined. Does that seem like a harvesting problem to you?
For many decades prior to the decline, the herd was so self-sustaining that in addition to natives taking what they wanted, non-indiginous could get 5 tags per year as well. And the herd maintained. There has been no significant increase in human population all the while. While I don't agree with the rights or hunting methods of natives, to proclaim they (or any hunting for that matter) are the cause of the decline is ridiculous. As to whether they and their hunting "rights" will prevent the herd from recovering is another topic altogether.