What were some effects of the columbian exchange? africa grew wealthy from the slave trade, the americas gained gold from europe, and the merchant class of europe was born. africa’s population declined, the americas flourished with plants from europe, and wealth flowed in the european economy. african society was torn apart by the slave trade, the americas exported finished goods to europe, and european countries invested in the american stock market. west africa began agricultural farming, the americas were introduced to horses, and europe started funding state banks.