I believe that the cash crops and the need for those cause a lot of slave trading. Americans used a lot of slaves to help build up cash quickly.
The crop failures were caused by late blight, a disease that destroys both the leaves and the edible roots, or tubers, of the potato plant. The causative agent of late blight is the water mold Phytophthora infestans. The Irish famine was the worst to occur in Europe in the 19th century
