If it had been left up to the Native Americans, the buffalo would never even have come close to being extinct. They took only what they needed and there weren't too many parts of the buffalo they didn't use. They knew when to quit. Unlike us, they weren't motivated by greed or high fashion.
Not true, at least in the idea that plains Indians lived in harmony with the buffalo. Of course, the plains Indians only existed in the first place because they were pushed out of more productive regions by competition with other tribes, who were in turn competing with European settlers. So if Europeans never showed up, Native American buffalo culture would not have existed anyway, or at least not for a long, long time.
Native Americans hunted the buffalo at an unsustainable rate by the 1780s and possibly as early as 1730, according to several studies. This is only 50 years after the creation of Native American horse culture that made life on the plains possible, based upon hunting bison exclusively. More importantly, the ecology of the plains simply couldn't support the bison herds and the presence of growing Native American populations post-1680 Pueblo Revolt, which introduced horses to Native Americans and moved them onto the Great Plains.
Certainly, the great herds were definitely in decline by the 1830s, long before the slaughters of the 1870s that get all the attention. Those simply capped off the extermination that had been going on for a century or more at that point.
Native American hunting is an undeniable factor in the decimation of bison. Famously, In 1856, an Indian Affairs officer reported that the five tribes in the upper Arkansas River basin, which totaled about 12,000 Native Americans, killed about 115,000 annually. All combined, Native Americans had been harvesting buffalo at an unsustainable rate. Much of this hunting was commercial in nature, Native Americans traded buffalo robes just as much as they traded beaver pelts (which nearly wiped out the beaver population too) and was driven by their desire for manufactured goods and arms they couldn't produce themselves. Still, according to estimates, simply subsistence harvesting of bison exceeded the ability of the herds to reproduce.
Another cause is ecological in nature - a great drought in the 1840s decimated some of the herds. Morever, the vast horse herds introduced by the Native Americans to the west meant that Native Americans now competed with buffalo for the same grazing and water resources. By the 1800s, horses represented class within Native American societies, and were used to barter. Tribes would have sizeable horse herds, tens of thousands in some cases.
This accelerated with the introduction of cattle into the region on a broad level through the use of oxen and cows on the Oregon and Santa Fe trails, also competing for the same resources, and introduced bovine diseases that bison had not been previously exposed to, which also ravaged the herds.
Finally, the introduction of the railroads in the west commercialized bison hunting in ways not possible before, and that simply finished off the herds.
It's been a while since I've looked at the literature, but studies by Elliot and West, along with Hamalain (spelling?) pretty much destroy the myth that Native Americans lived in harmony with the herds. Once the Native Americans became wholly dependent upon bison, rather than a more diversified existence, the tribal harvesting of buffalo outpaced the ability of herds to reproduce. It would have been a much slower extermination, but it would have still happened. The introduction of widespread Anglo-American activity in the West just made it happen much, much quicker.
I apologize for the long post, this topic is something I've looked at and lectured about to classes, as it invariably comes up when discussing the settlement of the West.
