Answer: The increased importation of African Slaves
Explanation:
The enslavement of the Natives happened for centuries after the Americas were colonized with millions of natives enslaved and sent to work in brutal conditions. Normally it was cheaper to use Native enslaved people than to import Africans but the Native population went on the decline due to disease, and continued war.
The colonists therefore turned to African slaves who had the advantage of being knowledgeable in Arable farming. With the increased importation of African slaves, the need for the enslavement of Natives was minimized.