What actions by whites destroyed the buffalo population?

Answer 1

Contrary to popular myth, the White buffalo hunters did not exterminate the bison; it was the wholesale slaughter by Native Americans that did it. The fault of the Anglos was in not providing the natives with accurate firearms. In his journal, buffalo hunter Billy Dixon lamented that his appeals for the army to provide rifles to the Indians fell on deaf ears. Lacking a way to selectively kill buffalo, the natives generally stuck with their time-honored method: driving an entire herd over a cliff and then taking a few choice cuts of meat from the mass of dead animals. The White hunters, who were selective in what they shot and tried to market everything they could (even the bones) were incensed by the wanton destruction of a valuable resource -- especially because they accurately foresaw that it would destroy their livelihood.

Answer 2

Over hunting for hides and meat. Often, trainloads of hunters would follow the great herds, killing indiscriminately.