Question

Why did Spanish colonists begin to rely more heavily on the Atlantic slave trade by the mid-1500s?

Answer 1

Spanish colonists began to rely more heavily on the Atlantic slave trade by the mid-1500s because they started massive construction products for which they needed a lot of free labor force, they also started trading with slaves and wanted to gain a lot of profit from it. 

Answer 2

Answer:

"Legal restrictions and outbreaks of disease made it difficult to get sufficient labor from indigenous populations."

I hope this helps guys!