How did the Columbian Exchange result in substantial reduction in the population of indigenous peoples

At the time of the exchange, there were contacts with each other, which was disastrous for the natives.

Explanation:

Contacts between Europeans and Native Americans were disastrous for the Indians. Coming to the New World, Europeans brought infectious diseases to which the natives had no immunity. Smallpox, flu, and similar diseases decimated the Indian tribes. A huge number of natives perished, and complete tribes disappeared.

yes.

explanation:

because it let the japanese know who had the upper hand in the war.

it was the first major victory for the colonists.