What were some effects the transatlantic slave trade had?
One effect was felt directly in Africa—the European need for chattel slavery made the slave trade grow exponentially. African tribes searched for more and more slaves and became dependent on European trade goods. This would eventually impoverish Africa, making it easier to colonize in the nineteenth century. While slavery had existed in Africa well before the time of Europeans, Europeans made slavery generational.
African slavery also made large-scale agriculture in the Americas practical. Native Americans were quick to run away from their European masters, and English indentured servants often died of mosquito-borne diseases. The Europeans used Africans because they were not familiar with the territory and, therefore, were less of a flight risk. Also, Africans were less likely to catch diseases like malaria. African labor made the sugarcane and tobacco fields possible, thus making a small number of whites very wealthy and enriching the imperial powers who owned the colonies.
Finally, the transatlantic slave trade enriched many port cities. Before the Revolutionary War, New York and Boston were common ports for slave catchers to stop and sell their cargo. This increased business around the cities, as the trade needed auctioneers to sell the slaves. There was also a need for taverns and boardinghouses for people coming from out of town to buy slaves. In the early days of America, the slave trade was a major part of the national economy, though some were complaining about the social issues that slavery raised even back then.
The effect of the transatlantic slave trade depends largely upon the area being studied.
For example in West Africa the effects of the slave trade were devastating; an estimated 12 to 15 millions people were forced to leave the continent by European slave traders, approximately two-thirds of these being adult males (ref: Christopher R. DeCorse West Africa During the Atlantic Slave Trade – 2001. Page 38). For the population left behind this meant a gender imbalance (i.e. more women than men) leading to economic and social difficulties (reduced workforce and eligible young men). This also had a political impact; communities would raid one another for slaves, in an effort to protect their own young men from slave traders and seeking economic recompense. This in turn led to an increase in localised warfare and civil unrest. There is an argument to be made that the destabilising effect of the transatlantic slave trade is still felt deeply in modern West Africa.
In Europe however the effect was very different; in Britain for example port towns such a London progressed as a direct result of slave trading. Profits were obtained not only from the sale of slaves but then also from the products those slaves produced such as sugar. The scale and success of the workforce established led to a rapid economic growth in the British economy. It also saw a rapid expansion of the British military and merchant navy. The introduction of cotton grown in the colonies led to the industrialisation of the cotton production process which in turn led to a single worker being able to produce two hundred times as much cotton cloth as before. Without the cheaply available raw cotton from the plantations in the Americas, this industrialisation would not have been possible nor encouraged. Essentially the transatlantic slave trade was an important factor in the industrial revolution.
For the Caribbean meanwhile the slave plantations became the primary source of income; the slave trade there led to a massive displaced population of forced migrants the impact of which can still be seen today in the form of racism and poverty, whilst on the other hand producing a great deal of wealth for the white population.