The slaves already had been exposed to the European diseases unlike the Natives so they had grown some immunity to them. They had experience in agriculture and cattle keeping, and they also brought new techniques in the agriculture field as well. The Americas had a bit more tropical climate than the European were used to, which caused them to get some tropical diseases, but the slave were used to the tropical climate and diseases. They were very good workers way better than the Native Americans and they could easily be taught how to work on a plantation. The slaves would not try to escape since they did not know the land like the Natives had and even if they did try to escape they would be easy to recapture due to the color of their skin. Slaves helped tremendously in many ways in the social developments in the Americas, but they mainly help in the areas of culture and the economy in their new lands. Some of the colonies in the Americas may not have even survived through and beyond this time period without the labor the slaves provided for