European diseases such as smallpox, measles, and yellow fever decimated the indigenous populations of the Americas, wiping out entire communities and leaving others vulnerable to European colonization. This led to a labor shortage in the Portuguese colonies, as the African slaves who had been brought over to work in the mines and fields were also dying from disease.
In response to this labor shortage, the Portuguese began to enslave the indigenous people of Brazil and other Portuguese colonies in South America. These indigenous peoples were forced to work in the same harsh conditions as the African slaves, and they often suffered from the same diseases and abuses.
The use of indigenous labor was not limited to the Portuguese; other European colonizers also enslaved indigenous peoples in the Americas, as well as in Africa and Asia. This practice continued for centuries and had a devastating impact on the indigenous populations of the world.